A radio service is a specific, tangible implementation of a wireless technology intended for a specific use. Wireless services are generally recognized and regulated by governmental organizations and may vary based on where the radio service is employed. Examples include Digital Television, Amateur radio, and 3G cellular services.A "radio service" differs from a "radio application" in that radio services are specific, recognized uses whereas radio applications are more general concepts, or rumored uses not widely substantiated. Examples of a radio application include general terms such as 'weather radar', or secret service radio channels whose use is rumored but whose implementation details are highly classified. A radio service also differs from a "wireless technology". A "wireless technology" is a specific body of knowledge used in implementing wireless products and radio services. Wireless technologies can generally can be distinguished from the specific implementations and conventions recognized by governments and regulatory organizations.
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The Landsat program is the longest running enterprise for acquisition of satellite imagery of Earth. On July 23, 1972 the Earth Resources Technology Satellite was launched. This was eventually renamed to Landsat. The most recent, Landsat 7, was launched on April 15, 1999. The instruments on the Landsat satellites have acquired millions of images. The images, archived in the United States and at Landsat receiving stations around the world, are a unique resource for global change research and applications in agriculture, cartography, geology, forestry, regional planning, surveillance, education and national security. Landsat 7 data has eight spectral bands with spatial resolutions ranging from 15 to 60 meters; the temporal resolution is 16 days.
Hughes Santa Barbara Research Center initiated design and fabrication of the first three MSS Multispectral Scanners in the same year man landed on the moon, 1969. The first prototype MSS was completed within nine months by fall of 1970 when it was tested by scanning Half Dome at Yosemite National Park.
The program was called the Earth Resources Technology Satellites Program when it was initiated in 1966, but the name was changed to Landsat in
Rural Radiotelephone Service (RRTS) provides basic, analog communications service between locations deemed so remote that traditional wireline service or service by other means is not feasible. RRTS uses channelized radio to provide radiotelephone services such as Basic Exchange Telephone Radio Service between a fixed subscriber location and a remote central office, private line service between a two fixed locations or interconnection between two or more central offices. RRTS does not enable mobile communications.
In the United States, the Federal Communications Commission issues initial Rural Radiotelephone Service licenses on a site-by-site basis. Once a license is issued, the licensee can sell or lease the license to another party.
The FCC service rules for Rural Radiotelephone are located in 47 C.F.R. Part 22 Subpart F.
In the United States, the ULS radio service code and description for Rural Radiotelephone licenses is CR – Rural Radiotelephone. The licensed spectrum is divided in 44 channels of 20 kHz each.
A traffic collision avoidance system or traffic alert and collision avoidance system (both abbreviated as TCAS) is an aircraft collision avoidance system designed to reduce the incidence of mid-air collisions between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of mid-air collision (MAC). It is a type of airborne collision avoidance system mandated by the International Civil Aviation Organization to be fitted to all aircraft with a maximum take-off mass (MTOM) of over 5700 kg (12,586 lbs) or authorized to carry more than 19 passengers.
Official definition from PANS-ATM (Nov 2007): ACAS / TCAS is an aircraft system based on secondary surveillance radar (SSR) transponder signals, which operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft that are equipped with SSR transponders.
In modern glass cockpit aircraft, the TCAS display may be integrated in the Navigation Display (ND) or Electronic Horizontal Situation
The Space-Based Infrared System (SBIRS) is a consolidated system intended to meet the United States' infrared space surveillance needs through the first two to three decades of the 21st century. The SBIRS program is designed to provide key capabilities in the areas of missile warning, missile defense and battlespace characterization.
SBIRS is an integrated "system of systems" that will include satellites in geosynchronous orbit (GEO), sensors hosted on satellites in highly elliptical orbit (HEO), and ground-based data processing and control. A complement of satellites in low earth orbit was planned as part of the program (SBIRS Low), but this has been moved into the STSS program. SBIRS ground software integrates infrared sensor programs of the U.S. Air Force (USAF) with new IR sensors. SBIRS continues to struggle with cost overruns, with Nunn-McCurdy breaches occurring in 2001 and 2005. By September 2007, the expected project cost had increased to $10.4 billion.
The original contract consisted of 2 HEO satellite sensors and 2-3 GEO sensors (and satellites) with an option to buy a total of 5 GEOs. In December 2005, following the third SBIRS Nunn-McCurdy violation, the government
Distance measuring equipment (DME) is a transponder-based radio navigation technology that measures slant range distance by timing the propagation delay of VHF or UHF radio signals.
Developed in Australia, it was invented by Edward George "Taffy" Bowen while employed as Chief of the Division of Radiophysics of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). Another engineered version of the system was deployed by Amalgamated Wireless Australasia Limited in the early 1950s operating in the 200 MHz VHF band. This Australian domestic version was referred to by the Federal Department of Civil Aviation as DME(D) (or DME Domestic), and the later international version adopted by ICAO as DME(I).
DME is similar to secondary radar, except in reverse. The system was a post-war development of the IFF (identification friend or foe) systems of World War II. To maintain compatibility, DME is functionally identical to the distance measuring component of TACAN.
Aircraft use DME to determine their distance from a land-based transponder by sending and receiving pulse pairs – two pulses of fixed duration and separation. The ground stations are typically co-located with VORs.
XM Satellite Radio (XM) is one of two satellite radio (SDARS) services in the United States and Canada, operated by Sirius XM Radio. It provides pay-for-service radio, analogous to cable television. Its service includes 73 different music channels, 39 news, sports, talk and entertainment channels, 21 regional traffic and weather channels and 23 play-by-play sports channels. XM channels are identified by Arbitron with the label "XM" (e.g. "XM32").
The company has its origins in the 1988 formation of the American Mobile Satellite Corporation (AMSC), a consortium of several organizations originally dedicated to satellite broadcasting of telephone, fax, and data signals. In 1992, AMSC established a unit called the American Mobile Radio Corporation dedicated to developing a satellite-based digital radio service; this was spun off as XM Satellite Radio Holdings, Inc. in 1999. The satellite service was officially launched on September 25, 2001.
On July 29, 2008, XM and former competitor Sirius Satellite Radio formally completed their merger, following U.S. Federal Communications Commission (FCC) approval, forming Sirius XM Radio, Inc. with XM Satellite Radio, Inc. as its subsidiary. On
The Aegis Combat System is an integrated naval weapons system developed by the Missile and Surface Radar Division of RCA, and now produced by Lockheed Martin. It uses powerful computers and radars to track and guide weapons to destroy enemy targets.
Initially used by the United States Navy, Aegis is now used also by the Japan Maritime Self-Defense Force, Spanish Navy, Royal Norwegian Navy, and Republic of Korea Navy. Over 100 Aegis-equipped ships have been deployed in five navies worldwide. The Royal Australian Navy has selected the Aegis system for placement on its new Air Warfare Destroyers, and it's part of NATO's European missile defence system.
The word "Aegis" is a reference that dates back to Greek mythology, with connotations of a protective shield, as the Aegis was the buckler (shield) of Athena.
The Aegis Combat System (ACS) is an advanced command and control (command and decision, or C&D, in Aegis parlance), and weapon control system (WCS) that uses powerful computers and radars to track and guide weapons to destroy enemy targets.
The ACS is composed of the Aegis Weapon System (AWS), the fast-reaction component of the Aegis Anti-Aircraft Warfare (AAW) capability, along
A video surveillance system consists of networks of closed-circuit television (CCTV), multiple display monitors and a team of security personnel. The deployment of CCTVs has to be carefully considered to provide a full coverage of key areas to be under surveillance.
An Intelligent Video Surveillance (IVS) System involves the use of video analytics in video surveillance system which automates the decision-making process of humans in identifying potential threats. The word ￢ﾀﾜintelligent￢ﾀﾝ signifies the use of smart programming software as assistance to humans during the surveillance process.
The first generation video surveillance involves CCTV cameras using video tapes for recording. A multiplexer serves the purpose of collecting various images for displaying on monitors which are monitored by security officials only.
The second generation video surveillance replaces video tapes with digital video recorder (DVR). Automatic event detection enables recordings to be triggered by motion events in the scene to save up memory space.
The third generation video surveillance involves more advanced technologies and the integration of intelligent algorithms. IP cameras were used in
A micro air vehicle (MAV), or micro aerial vehicle, is a class of unmanned aerial vehicles (UAV) that has a size restriction and may be autonomous. Modern craft can be as small as 15 centimetres. Development is driven by commercial, research, government, and military purposes; with insect-sized aircraft reportedly expected in the future. The small craft allows remote observation of hazardous environments inaccessible to ground vehicles. MAVs have been built for hobby purposes, such as aerial robotics contests and aerial photography.
A new trend in the MAV community is to take inspiration from flying insects or birds to achieve unprecedented flight capabilities. Biological systems are not only interesting to MAV engineers for their use of unsteady aerodynamics with flapping wings; they are increasingly inspiring engineers for other aspects such as distributed sensing and acting, sensor fusion and information processing. Symposiums bringing together biologists and aerial roboticists have been held in 2007 and some books have recently been published on this topic.
In January 2010, the Tamkang University (TKU) in Taiwan realized autonomous control of the flight altitude of an 8-gram,
The industrial, scientific and medical (ISM) radio bands are radio bands (portions of the radio spectrum) reserved internationally for the use of radio frequency (RF) energy for industrial, scientific and medical purposes other than communications. Examples of applications in these bands include radio-frequency process heating, microwave ovens, and medical diathermy machines. The powerful emissions of these devices can create electromagnetic interference and disrupt radio communication using the same frequency, so these devices were limited to certain bands of frequencies. In general, communications equipment operating in these bands must tolerate any interference generated by ISM equipment, and users have no regulatory protection from ISM device operation.
Despite the intent of the original allocation, in recent years the fastest-growing uses of these bands have been for short-range, low power communications systems. Cordless phones, Bluetooth devices, NFC devices, and wireless computer networks all use the ISM bands.
The ISM bands are defined by the ITU-R in 5.138, 5.150, and 5.280 of the Radio Regulations. Individual countries' use of the bands designated in these sections may
A picocell is a small cellular basestation typically covering a small area, such as in-building (offices, shopping malls, train stations, stock exchanges, etc.), or more recently in-aircraft. In cellular networks, picocells are typically used to extend coverage to indoor areas where outdoor signals do not reach well, or to add network capacity in areas with very dense phone usage, such as train stations. Picocells provide coverage and capacity in areas difficult or expensive to reach using the more traditional Macrocell approach.
In cellular wireless networks, such as GSM, the picocell base station is typically a low cost, small (typically the size of a ream of A4 paper), reasonably simple unit that connects to a Base Station Controller (BSC). Multiple picocell 'heads' connect to each BSC: the BSC performs radio resource management and hand-over functions, and aggregates data to be passed to the Mobile Switching Centre (MSC) and/or the Gateway GPRS Support Node (GGSN).
Connectivity between the picocell heads and the BSC typically consists of in-building wiring. Although originally deployed systems (1990s) used PDH links such as E1/T1 links, more recent systems use Ethernet cabling.
iBurst (or HC-SDMA, High Capacity Spatial Division Multiple Access) is a wireless broadband technology originally developed by ArrayComm. It optimizes the use of its bandwidth with the help of smart antennas. Kyocera is the manufacturer of iBurst devices.
iBurst is a mobile broadband wireless access system that was first developed by ArrayComm, and announced with partner Sony in April 2000. It was adopted as the High Capacity – Spatial Division Multiple Access (HC-SDMA) radio interface standard (ATIS-0700004-2005) by the Alliance for Telecommunications Industry Solutions (ATIS). The standard was prepared by ATIS’ Wireless Technology and Systems Committee’s Wireless Wideband Internet Access subcommittee and accepted as an American National Standard in 2005.
HC-SDMA was announced as considered by ISO TC204 WG16 for the continuous communications standards architecture, known as Communications, Air-interface, Long and Medium range (CALM), which ISO is developing for intelligent transport systems (ITS). ITS may include applications for public safety, network congestion management during traffic incidents, automatic toll booths, and more. An official liaison was established between WTSC
A personal area network (PAN) is a computer network used for communication among computerized devices, including telephones and personal digital assistants. PANs can be used for communication among the personal devices themselves (intrapersonal communication), or for connecting to a higher level network and the Internet (an uplink). A wireless personal area network (WPAN) is a PAN carried over wireless network technologies such as IrDA, Bluetooth, Wireless USB, Z-Wave, ZigBee, or even Body Area Network. The reach of a WPAN varies from a few centimeters to a few meters. A PAN may also be carried over wired computer buses such as USB and FireWire.
A wireless personal area network (WPAN) is a personal area network — a network for interconnecting devices centered around an individual person's workspace — in which the connections are wireless. Wireless PAN is based on the standard IEEE 802.15. The two kinds of wireless technologies used for WPAN are Bluetooth and Infrared Data Association.
A WPAN could serve to interconnect all the ordinary computing and communicating devices that many people have on their desk or carry with them today; or it could serve a more specialized purpose such
Specific Area Message Encoding (SAME) is the protocol used to encode the Emergency Alert System (EAS) and NOAA Weather Radio's SAME Public Warning System in the U.S. and Weatheradio Canada in Canada.
From the 1960s to the 1980s, a special feature of the NOAA Weather Radio system was the transmission of a single tone at 1050 Hz prior to the broadcast of any message alerting the general public of significant weather events. This became known as the Warning Alarm Tone (WAT). Although it has served NOAA Weather Radio well, there were many drawbacks: without staff at media facilities to manually evaluate the need to rebroadcast a Weather Radio message using the Emergency Broadcast System (EBS), automatic rebroadcasting of all messages preceded by just the WAT was unacceptable and impractical. Even if stations and others with that type of need were willing to allow for this type of automatic capture, assuming the events for activation were critical, there was no way for automated equipment at the station to know when the message was complete and restore it back to normal operation.
In 1985, the National Weather Service forecast offices began experimenting with putting special digital
Fixed wireless is the operation of wireless devices or systems used to connect two fixed locations (e.g., buildings) with a radio or other wireless link, such as laser bridge. Usually, fixed wireless is part of a wireless LAN infrastructure. The purpose of a fixed wireless link is to enable data communications between the two sites or buildings. Fixed wireless data (FWD) links are often a cost-effective alternative to leasing fiber or installing cables between the buildings.
The point-to-point signal transmissions occur through the air over a terrestrial microwave platform rather than through copper or optical fiber; therefore, fixed wireless does not require satellite feeds or local telephone service. The advantages of fixed wireless include the ability to connect with users in remote areas without the need for laying new cables and the capacity for broad bandwidth that is not impeded by fiber or cable capacities. Fixed wireless devices usually derives their electrical power from the public utility mains, unlike mobile wireless or portable wireless devices which tend to be battery powered.
Fixed wireless services typically use a directional radio antenna on each end of the signal
Geophysics ( /dʒiːoʊfɪzɪks/) is the physics of the Earth and its environment in space; also the study of the Earth using quantitative physical methods. The term geophysics sometimes refers only to the geological applications: Earth's shape; its gravitational and magnetic fields; its internal structure and composition; its dynamics and their surface expression in plate tectonics, the generation of magmas, volcanism and rock formation. However, modern geophysics organizations use a broader definition that includes the hydrological cycle including snow and ice; fluid dynamics of the oceans and the atmosphere; electricity and magnetism in the ionosphere and magnetosphere and solar-terrestrial relations; and analogous problems associated with the Moon and other planets.
Although geophysics was only recognized as a separate discipline in the 19th century, its origins go back to ancient history. The first magnetic compasses date back to the fourth century BC and the first seismoscope was built in 132 BC. Geophysical methods were developed for navigation; Isaac Newton applied his theory of mechanics to the tides and the precession of the equinox; and instruments were developed to measure
The Tracking and Data Relay Satellite System (TDRSS) is a network of American communications satellites (each called a Tracking and Data Relay Satellite (TDRS)) and ground stations used by NASA for space communications. The system was designed to replace an existing network of ground stations that had supported all of NASA's manned flight missions. The prime design goal was to increase the time spacecraft were in communication with the ground and improve the amount of data that could be transferred. Many Tracking and Data Relay Satellites were launched in the 1980s and 1990s with the Space Shuttle and made use of the Inertial Upper Stage, a two-stage solid rocket booster developed for the shuttle. Other TDRS were launched by Atlas IIa and Atlas V rockets.
The most recent generation of satellites provides ground reception rates of 300 Mbit/s in the Ku- and Ka-bands and 800 Mbit/s in the S-band.
The term TDRSS is analogous to Space Network.
To satisfy the requirement for long-duration, highly-available space-to-ground communications, NASA created the Spacecraft Tracking and Data Acquisition Network (STADAN). Consisting of parabolic dish antennas and telephone switching equipment
Space-based radar refers to space-borne radar systems that may have any of a variety of purposes. A number of earth-observing radar satellites, such as RadarSat, have employed synthetic aperture radar (SAR) to obtain terrain and land-cover information about the Earth.
Space-Based Radar (SBR) is a proposed constellation of active radar satellites for the United States Department of Defense. The SBR system would allow detection and tracking of aircraft, ocean-going vessels (similar to the Soviet RORSAT program), and potentially land vehicles from space. This information would then be relayed to regional and national command centers, as well as E-10 MC2A airborne command posts.
Use of radar sensor for Earth observation purposes was started by NASA/JPL's Seasat satellite, which carried 3 different radar sensors:
After Seasat, SARs, altimeters and scatterometers have been flown on several other space missions.
While the SAR is, in principle, similar to its airborne counterparts (with the advantage of the increased coverage and worldwide access offered by the satellite platform), the other two are specific to satellite operations.
A satellite radar-altimeter is a nadir-looking radar with
High Energy Radio Frequency weapons (HERF) or High Power Radio Frequency weapons (HPRF) are weapons that use high intensity radio waves to disrupt electronics. They are a type of directed-energy weapon. They operate similarly to electromagnetic pulse (EMP) devices, by inducing destructive voltage within electronic wiring. They are usually directional and can be focused on a specific target using a parabolic reflector. Faraday cages may be used to provide protection from most HERF and EMP effects.
Loren Thompson, chief operating officer of the Lexington Institute in Virginia states that: “The relevant [electromagnetic weapon] technology is well within the grasp of some countries and transnational terrorist groups," and further states that U.S. hardware is susceptible to microwave and other directed-energy weapons.
Suitable materials and tools to create electromagnetic weapons are commonly available. "The threat of electromagnetic bomb proliferation is very real."
In the United States of America, the University of Texas-Austin Institute for Advanced Technology (IAT) conducts basic research to advance electrodynamics and hypervelocity physics related to electromagnetic weapons.
The Goldstone Deep Space Communications Complex (GDSCC) — commonly called the Goldstone Observatory — is located in California's Mojave Desert. Operated by ITT Corporation for the Jet Propulsion Laboratory, its main purpose is to track and communicate with space missions. It includes the Pioneer Deep Space Station, which is a U.S. National Historic Landmark. The current observatory is part of NASA's Deep Space Network. The Goldstone Deep Space Communications Complex is one of just three in the world; the others being the Madrid Deep Space Communication Complex and the Canberra Deep Space Communication Complex.
Goldstone antennas have also been used as sensitive radio telescopes for such scientific investigations as mapping quasars and other celestial radio sources; radar mapping planets, the Moon, comets and asteroids; spotting comets and asteroids with the potential to strike Earth; and the search for ultra-high energy neutrino interactions in the moon by using large-aperture radio antennas.
It is commonly believed that the first U.S. satellite, Explorer I, was confirmed to be in orbit by the use of the phrase "Goldstone has the bird". However, Goldstone was not in operation at
High-definition television (HDTV) provides a resolution that is substantially higher than that of standard-definition television.
HDTV may be transmitted in various formats:
The letter "p" here stands for progressive scan while "i" indicates interlaced.
When transmitted at two megapixels per frame, HDTV provides about five times as many pixels as SD (standard-definition television).
The term high definition once described a series of television systems originating from the late 1930s; however, these systems were only high definition when compared to earlier systems that were based on mechanical systems with as few as 30 lines of resolution. The on going competition between companies and nations to create true "HDTV" spanned the entire 20th century, as each new system became more HD than the last.
The British high-definition TV service started trials in August 1936 and a regular service on 2 November 1936 using both the (mechanical) Baird 240 line and (electronic) Marconi-EMI 405 line (377i) systems. The Baird system was discontinued in February 1937. In 1938 France followed with their own 441-line system, variants of which were also used by a number of other countries. The US NTSC
Specialized Mobile Radio (SMR) may be an analog or digital trunked two-way radio system, operated by a service in the VHF, 220, UHF, 700, 800 or 900 MHz bands. Some systems with advanced features are referred to as an Enhanced Specialized Mobile Radio, (ESMR). Specialized Mobile Radio is a term defined in US Federal Communications Commission (FCC) regulations. The term is of US regulatory origin but may be used in other regions to describe similar commercial systems which offer a radio communications service to businesses.
SMRs were created when the Federal Communications Commission began to license business and commercial 800 MHz two-way radio systems in the late 1970s.
Any company, such as a taxi service, towing service, or construction company, may use an SMR service. These concerns may rent radios from the SMR operator or may buy compatible radios. SMR systems use differing protocols, frequency ranges, and modulation schemes: not every radio is compatible with every SMR system.
These systems generally consist of one or more repeaters used to maintain communications between a dispatch fleet of mobile or hand-held walkie talkie radios. One- to five-channel systems may be
1worldspace, formerly known as 'WorldSpace', is an almost but not yet completely defunct satellite radio network that in its heyday provided service to over 170,000 subscribers in eastern and southern Africa, the Middle East, and much of Asia with 96% coming from India. Timbre Media along with Saregama India plan to relaunch the company.
However a mystery about the final fate of the original Worldspace satellite radio service still remains because despite the company's very public insolvency and the liquidation of all of its various commercial entities two or more years ago (in 2008/09). The company's Afristar and Asiastar satellites still continue to remain in geostationary orbit to this day. Currently, the channels WRN 1 and WRN 2 can be received on Afristar with audio. On AsiaStar, there are 2 channels broadcasting (the old Maestro channel and Sai Global Harmony which is an Indian religious channel). The precise commercial basis on which the Afristar and Asiastar satellites currently continue to be maintained in working satellite orbit by Intelsat is not known at the present time.
The company headquarters were located in Silver Spring, MD and additional studios were located in
Wi-Fi ( /ˈwaɪfaɪ/, also spelled Wifi or WiFi) is a popular technology that allows an electronic device to exchange data wirelessly (using radio waves) over a computer network, including high-speed Internet connections. The Wi-Fi Alliance defines Wi-Fi as any "wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards". However, since most modern WLANs are based on these standards, the term "Wi-Fi" is used in general English as a synonym for "WLAN".
A device that can use Wi-Fi (such as a personal computer, video-game console, smartphone, tablet, or digital audio player) can connect to a network resource such as the Internet via a wireless network access point. Such an access point (or hotspot) has a range of about 20 meters (65 feet) indoors and a greater range outdoors. Hotspot coverage can comprise an area as small as a single room with walls that block radio waves or as large as many square miles — this is achieved by using multiple overlapping access points.
"Wi-Fi" is a trademark of the Wi-Fi Alliance and the brand name for products using the IEEE 802.11 family of standards. Only Wi-Fi products
The Deep Space Network, or DSN, is a world-wide network of large antennas and communication facilities that supports interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected Earth-orbiting missions. DSN is part of the NASA Jet Propulsion Laboratory (JPL). Other similar networks include ESTRACK of the European Space Agency, the Soviet Deep Space Network, the Indian Deep Space Network, and the Chinese Deep Space Network.
Tracking vehicles in deep space is quite different from tracking missions in low Earth orbit (LEO). Deep space missions are visible for long periods of time from a large portion of the Earth's surface, and so require few stations (the DSN has only three main sites). These few stations, however, require huge antennas, ultra-sensitive receivers, and powerful transmitters in order to transmit and receive over the vast distances involved.
Deep space is defined in two different ways. The first is when a mission gets sufficiently far from Earth that it is always in view of one of the tracking stations. This distance, about 20-30,000 km or 10-16,000 miles, was
Sirius Satellite Radio is a satellite radio (SDARS) service operating in North America, owned by Sirius XM Radio.
Headquartered in New York City, with smaller studios in Los Angeles and Memphis, Sirius was officially launched on July 1, 2002 and currently provides 69 streams (channels) of music and 65 streams of sports, news and entertainment to listeners. Music streams on Sirius carry a wide variety of genres, broadcasting 24 hours daily, commercial-free, and uncensored. A subset of Sirius music channels is included as part of the Dish Network satellite television service. Sirius channels are identified by Arbitron with the label "SR" (e.g. "SR120", "SR9", "SR17").
Its business model is to provide pay-for-service radio, analogous to the business model for premium cable television. Music channels are presented without commercials while talk channels, such as Howard Stern's Howard 100 and Howard 101 and The Opie & Anthony Channel, do have regular commercials. At approximately 6 minutes per hour, the number of commercials are still less than the average on terrestrial radio or television. Furthermore, all channels are free from FCC content regulation, thus songs are played unedited
Direct-To-Home is a term that describes satellite television service that is delivered via communication satellite. The TV signal is delivered from satellite's transponder direct to receiving antenna of TV set, without relay of re-broadcasting stations.See also Direct Broadcast Satellite.
DirecTV, branded as DIRECTV, is an American direct broadcast satellite service provider and broadcaster based in El Segundo, California. Its satellite service, launched on June 17, 1994, transmits digital satellite television and audio to households in the United States, Ibero-America, and the Anglophone Caribbean. Its primary competitors are Dish Network and cable television providers. At the end of 2011, DirecTV had 19.89 million subscribers.
DirecTV provides television and audio services to subscribers through satellite transmissions. Services include the equivalent of many local television stations, broadcast television networks, subscription television services, satellite radio services, and private video services. Subscribers have access to hundreds of channels, so its competitors are cable television service and other satellite-based services.
Most subscribers use reception antennas which are much smaller than the first generation antennas, which were typically a few yards (meters) across. Advances in antenna technology, including fractal antenna layouts, have allowed a general reduction in antenna size across all industries and applications. Receiving equipment includes a
The Unlicensed National Information Infrastructure (U-NII) radio band is part of the radio frequency spectrum used by IEEE-802.11a devices and by many wireless ISPs. It operates over three ranges:
Wireless ISPs generally use 5.725-5.825 GHz.
U-NII is an FCC regulatory domain for 5- GHz wireless devices. U-NII power limits are defined by the United States CFR Title 47 (Telecommunication), Part 15 - Radio Frequency Devices, Subpart E - Unlicensed National Information Infrastructure Devices, Paragraph 15.407 - General technical requirements. Regulatory use in individual countries may differ.
The European HiperLAN standard operates in same frequency band as the U-NII.
Except where noted, all information taken from Annex J of IEEE 802.11-2007 modified by amendments k, y and n.
Countries apply their own regulations to both the allowable channels, allowed users and maximum power levels within these frequency ranges. Consult your local authorities as these regulations may be out of date as they are subject to change at any time.
In 2007 the FCC (United States) began requiring that devices in operating in channels 52, 56, 60 and 64 must have dynamic frequency selection (DFS) capabilities.
Airfone was a brand of air-ground radiotelephone service offered by Verizon. Airfone allows passengers to make telephone calls in-flight. An Airfone telephone is usually located in the seatback of the seat in front of the passenger, there may only be one per row in coach class, while first class may have one per seat. Airfone phone calls are usually quite expensive compared to ground-based telephone calls, costing $3.99 per call and $4.99 per minute in 2006.
Bell Mobility used the Airfone technology on Air Canada flights, but brands its service Skytel (no relation to the Verizon-owned paging firm of the same name).
Calls were often discounted or free for customers of airplane-based catalogs like Sky Mall, and Verizon Wireless subscribers can pay $10 per month and 10 cents a call or a flat 69 cents per call with no monthly fee. Airfone could be used for very slow modem calls, and attempts at data service were made in 2003 and 2004 using an on-board email proxy server.
Many of the in-flight calls made by victims of 9/11 were made over Airfone and Air One.
Airfone's primary competitor was Air One, operated by AT&T Wireless division Claircom Communications Group, and was available
A transient electromagnetic device (TED) is a device that emits a transient pulse of electromagnetic radiation of a few picoseconds in length. TEDs generally use spark gap switches, in oil or in pressurized gas pulse storage lines, or explosively pumped flux compression generator.
TEDs have been examined by the US military for their threat potential as a weapon that harms computer system.
The Joint Tactical Information Distribution System (JTIDS) is an L band TDMA network radio system used by the United States armed forces and their allies to support data communications needs, principally in the air and missile defense community. It provides high-jam-resistance, high-speed, crypto-secure computer-to-computer connectivity in support of every type of military platform from Air Force fighters to Navy submarines. The full development of JTIDS commenced in 1981 when a contract was placed with Singer-Kearfott (later GEC-Marconi Electronic Systems, now BAE Systems E&IS). Fielding proceeded slowly throughout the late 1980s and early 1990s with rapid expansion (following 9/11) in preparation for Operation Enduring Freedom (Afghanistan) and Operation Iraqi Freedom. Development is now carried out by Data Link Solutions, a joint BAE/Rockwell Collins company.
JTIDS is one of the family of radio equipment implementing what is called Link 16. Link 16, a highly-survivable radio communications design to meet the most stringent requirements of modern combat, provides reliable Situational Awareness (SA) for fast-moving forces. Link 16 equipment has proven, in detailed field
The air traffic control radar beacon system (ATCRBS) is a system used in air traffic control (ATC) to enhance surveillance radar monitoring and separation of air traffic. ATCRBS assists ATC surveillance radars by acquiring information about the aircraft being monitored, and providing this information to the radar controllers. The controllers can use the information to identify radar returns from aircraft (known as targets) and to distinguish those returns from ground clutter.
The system consists of transponders, installed in aircraft, and secondary surveillance radars (SSRs), installed at air traffic control facilities. The SSR is co-located with the primary surveillance radar, or PSR. These two radar systems work in conjunction to produce a synchronized surveillance picture. The SSR transmits interrogations and listens for any replies. Transponders that receive an interrogation decode it, decide whether to reply, and then respond with the requested information when appropriate. Note that in common informal usage, the term "SSR" is sometimes used to refer to the entire ATCRBS system, however this term (as found in technical publications) properly refers only to the ground radar
A satellite navigation or SAT NAV system is a system of satellites that provide autonomous geo-spatial positioning with global coverage. It allows small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few metres using time signals transmitted along a line-of-sight by radio from satellites. Receivers calculate the precise time as well as position, which can be used as a reference for scientific experiments. A satellite navigation system with global coverage may be termed a global navigation satellite system or GNSS.
As of October 2011, only the United States NAVSTAR Global Positioning System (GPS) and the Russian GLONASS are fully globally operational GNSSs. China is in the process of expanding its regional Beidou navigation system into the global Compass navigation system by 2020. The European Union's Galileo positioning system is a GNSS in initial deployment phase, scheduled to be fully operational by 2020 at the earliest. Several countries including France, Japan and India. are in the process of developing regional navigation systems.
Global coverage for each system is generally achieved by a satellite constellation of 20–30 medium
A ground proximity warning system (GPWS) is a system designed to alert pilots if their aircraft is in immediate danger of flying into the ground or an obstacle. The United States Federal Aviation Administration defines GPWS as a type of terrain awareness warning system (TAWS). More advanced systems, introduced in 1996, are known as enhanced ground proximity warning systems (EGPWS), although sometimes confusingly called terrain awareness warning systems.
In the late 1960s, a series of controlled flight into terrain (CFIT) accidents took the lives of hundreds of people. (A CFIT accident is one where a properly functioning airplane under the control of a fully qualified and certificated crew is flown into terrain (or water or obstacles) with no apparent awareness on the part of the crew.)
Beginning in the early 1970s, a number of studies looked at the occurrence of CFIT accidents. Findings from these studies indicated that many such accidents could have been avoided if a warning device called a ground proximity warning system (GPWS) had been used. As a result of these studies and recommendations from the U.S. National Transportation Safety Board (NTSB), in 1974 the FAA required all
A bhangmeter is a non-imaging radiometer installed on reconnaissance and navigation satellites to detect atmospheric nuclear detonations and determine the yield of the nuclear weapon.
The bhangmeter was invented, and the first proof-of-concept device was built, in 1948 to measure the nuclear test detonations of Operation Sandstone. Prototype and production instruments were later built by EG&G, and the name “bhangmeter” was coined in 1950. Bhangmeters became standard instruments used to observe US nuclear tests. A Mod II bhangmeter was developed to observe the detonations of Operation Buster-Jangle (1951) and Operation Tumbler-Snapper (1952).
US president John F. Kennedy and the First Secretary of the Communist Party of the Soviet Union Nikita Khrushchev signed the Partial Test Ban Treaty on August 5, 1963, under the condition that each party could use its own technical means to monitor the ban on nuclear testing in the atmosphere or in outer space.
Bhangmeters were first installed, in 1961, aboard a modified US KC-135B aircraft monitoring the pre-announced Soviet test of Tsar Bomba.
The Vela satellites were the first space-based observation devices jointly developed by the U.S. Air
Differential Global Positioning System (DGPS) is an enhancement to Global Positioning System that provides improved location accuracy, from the 15-meter nominal GPS accuracy to about 10 cm in case of the best implementations.
DGPS uses a network of fixed, ground-based reference stations to broadcast the difference between the positions indicated by the satellite systems and the known fixed positions. These stations broadcast the difference between the measured satellite pseudoranges and actual (internally computed) pseudoranges, and receiver stations may correct their pseudoranges by the same amount. The digital correction signal is typically broadcast locally over ground-based transmitters of shorter range.
The term can refer both to the generalized technique as well as specific implementations using it. For instance, the United States Coast Guard (USCG) and Canadian Coast Guard (CCG) each run such a system in the U.S. and Canada on the longwave radio frequencies between 285 kHz and 325 kHz near major waterways and harbors. The USCG's DGPS system is nationwide and comprises 86 broadcast sites located throughout the inland and coastal portions of the United States including Alaska,
HughesNet (formerly DirecWay) is the brand name of the one-way and two-way satellite broadband Internet technology and service in U.S. and Europe owned by Hughes Network Systems. The service was originally called DirecPC and was only available as a one-way satellite Internet option, as uploading was accomplished with a dial-up modem connection. The original consumer DirecPC service launched in October 1996
On March 27, 2006, DirecWay officially changed its name to HughesNet. The previous DirecWay name was fully retired on April 22, 2006. HughesNet solutions and services are marketed directly by HUGHES and its authorized resellers and distributors throughout North America, Europe, India and Brazil. In all other regions of the world, Hughes products and services are available from a growing family of value-added providers and resellers.
An airborne early warning and control (AEW&C) system is an airborne radar system designed to detect aircraft, ships and vehicles at long ranges and control and command the battle space in an air engagement by directing fighter and attack aircraft strikes. AEW&C units are also used to carry out surveillance, including over ground targets and frequently perform C2BM (command and control, battle management) functions similar to an Airport Traffic Controller given military command over other forces. Used at a high altitude, the radars on the aircraft allow the operators to distinguish between friendly and hostile aircraft hundreds of miles away.
AEW&C aircraft are used for both defensive and offensive air operations, and are to the NATO and USA forces trained or integrated Air Forces what the Command Information Center is to a Navy Warship, plus a highly mobile and powerful radar platform. The system is used offensively to direct fighters to their target locations, and defensively in order to counter attacks by enemy forces, both air and ground. So useful is the advantage of command and control from a high altitude, the United States Navy operates AEW&C aircraft off its Supercarriers
Mars Pathfinder (MESUR Pathfinder) was an American spacecraft that landed a base station with a roving probe on Mars in 1997. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight (10.6 kg/23 lb) wheeled robotic Mars rover named Sojourner.
Launched on December 4, 1996 by NASA aboard a Delta II booster a month after the Mars Global Surveyor was launched, it landed on July 4, 1997 on Mars's Ares Vallis, in a region called Chryse Planitia in the Oxia Palus quadrangle. The lander then opened, exposing the rover which conducted many experiments on the Martian surface. The mission carried a series of scientific instruments to analyze the Martian atmosphere, climate, geology and the composition of its rocks and soil. It was the second project from NASA's Discovery Program, which promotes the use of low-cost spacecraft and frequent launches under the motto "cheaper, faster and better" promoted by the then administrator, Daniel Goldin. The mission was directed by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology, responsible for NASA's Mars Exploration Program. The project manager was JPL's Tony Spear.
This mission was
Terminal High Altitude Area Defense (THAAD), formerly Theater High Altitude Area Defense, is a United States Army system to shoot down short, medium, and intermediate ballistic missiles in their terminal phase using a hit-to-kill approach. The missile carries no warhead but relies on the kinetic energy of the impact. THAAD was designed to hit Scuds and similar weapons, but also has a limited capability against ICBMs.
The THAAD system is being designed, built, and integrated by Lockheed Martin Space Systems acting as prime contractor. Key subcontractors include Raytheon, Boeing, Aerojet, Rocketdyne, Honeywell, BAE Systems, and MiltonCAT. Development was budgeted at over USD$700 million for 2004.
Although originally a U.S. Army program, THAAD has come under the umbrella of the Missile Defense Agency. The Navy has a similar program, the sea-based Aegis Ballistic Missile Defense System. THAAD was originally scheduled for deployment in 2012, but initial deployment took place May 2008.
The THAAD missile defense concept was proposed in 1987, with a formal request for proposals submitted to industry in 1990. In September 1992, the U.S. Army selected Lockheed Martin as prime contractor for
The Tropical Rainfall Measuring Mission (TRMM) is a joint space mission between NASA and the Japan Aerospace Exploration Agency (JAXA) designed to monitor and study tropical rainfall. The term refers to both the mission itself and the satellite that the mission uses to collect data. TRMM is part of NASA's Mission to Planet Earth, a long-term, coordinated research effort to study the Earth as a global system. The satellite was launched on November 27, 1997 from the Tanegashima Space Center in Tanegashima, Japan.
The Precipitation Radar is the first spaceborne instrument designed to provide three-dimensional maps of storm structure. The measurements yield information on the intensity and distribution of the rain, on the rain type, on the storm depth and on the height at which the snow melts into rain. The estimates of the heat released into the atmosphere at different heights based on these measurements can be used to improve models of the global atmospheric circulation.
The TRMM Microwave Imager (TMI) is a passive microwave sensor designed to provide quantitative rainfall information over a wide swath under the TRMM satellite. By carefully measuring the minute amounts of microwave
The Air Force Satellite Control Network (AFSCN) provides support for the operation, control, and maintenance of a variety of United States Department of Defense and some non-DoD satellites. This involves continual execution of Telemetry, Tracking, and Commanding (TT&C) operations. In addition, the AFSCN provides prelaunch checkout and simulation, launch support, and early orbit support while satellites are in initial or transfer orbits and require maneuvering to their final orbit. The AFSCN provides tracking data to help maintain the catalog of space objects and distributes various data such as satellite ephemeris, almanacs, and other information.
The AFSCN consists of satellite control centers, tracking stations, and test facilities located around the world. Satellite Operations Centers (SOCs) are located at Schriever Air Force Base near Colorado Springs, Colorado, and various other locations throughout the continental United States. These SOCs are manned around the clock and are responsible for the command and control of their assigned satellite systems. The SOCs are linked to remote tracking stations (RTSs) around the world. Space vehicle checkout facilities are used to test
The Allen Telescope Array (ATA), formerly known as the One Hectare Telescope (1hT), was a joint effort by the SETI Institute and the Radio Astronomy Laboratory (RAL) at the University of California, Berkeley to construct a radio interferometer that is dedicated to astronomical observations and a simultaneous search for extraterrestrial intelligence. UC Berkeley completed divestment from the project in April 2012 and the facility is now managed by SRI International, an independent, nonprofit research institute.
The ATA is under construction at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California. When completed, the array is expected to consist of 350 antennas. The first phase with 42 antennas (ATA-42) is complete and became operational on 11 October 2007. However, in April 2011, the ATA was placed in operational hibernation due to funding shortfalls. In August 2011, short-term funding was found, and operation of the ATA was resumed on December 5, 2011.
First conceived by SETI pioneer Frank Drake, the idea has been a dream of the SETI Institute for years. However, it was not until early 2001 that research and development commenced after a
The Broadband Global Area Network (BGAN) is a global Satellite Internet Network with telephony using portable terminals. The terminals are normally used to connect a laptop computer to broadband Internet in remote locations, although as long as line-of-sight to the satellite exists, the terminal can be used anywhere. The value of BGAN terminals is that unlike other satellite Internet services which require bulky and heavy satellite dishes to connect, a BGAN terminal is about the size of a laptop and thus can be carried easily. The network is provided by Inmarsat and uses three geostationary satellites called I-4 to provide almost global coverage.
Downlink speeds of high-end BGAN terminals are up to 492 kbit/s and upload speeds are also up to 492 kbit/s - Best Effort as BGAN Background IP (BIP) is a contended (shared) channel. As with all geosynchronous satellite connections, latency is an issue. Common latency is 1–1.5 seconds round trip for the Background IP service. It is slightly better for the Streaming services at 800 ms – 1 second. This latency is mainly due to the great distance that has to be traveled before a packet can reach the Internet, but is slightly exacerbated by
A heart rate monitor is a personal monitoring device which allows a subject to measure his or her heart rate in real time or record his or her heart rate for later study. It is largely used by performers of various types of physical exercise.
Early models consisted of a monitoring box with a set of electrode leads which attached to the chest. The first wireless EKG Heart rate monitor was invented in 1977 as a training aid for the Finnish National Cross Country Ski team and as 'intensity training' became a popular concept in athletic circles in the mid-80s, retail sales of wireless personal heart monitors started from 1983.
Modern heart rate monitors usually comprise two elements: a chest strap transmitter and a wrist receiver or mobile phone (which usually doubles as a watch or phone). In early plastic straps water or liquid was required to get good performance. Later units have used conductive smart fabric with built-in microprocessors which analyse the EKG signal to determine heart rate.
Strapless heart rate monitors now allow the user to just touch two sensors on a wristwatch display for a few seconds to view their heart rate. These are popular for their comfort and ease of use
The Personal Handy-phone System (PHS), also marketed as the Personal Access System (PAS) and commercially branded as Xiaolingtong (Chinese: 小灵通) in Mainland China, is a mobile network system operating in the 1880–1930 MHz frequency band, used mainly in Japan, China, Taiwan, and some other Asian countries and regions.
PHS is essentially a cordless telephone like DECT, with the capability to handover from one cell to another. PHS cells are small, with transmission power of base station a maximum of 500 mW and range typically measures in tens or at most hundreds of metres (some can range up to about 2 kilometres in line-of-sight), contrary to the multi-kilometre ranges of CDMA and GSM. This makes PHS suitable for dense urban areas, but impractical for rural areas, and the small cell size also makes it difficult if not impossible to make calls from rapidly moving vehicles.
PHS uses TDMA/TDD for its radio channel access method, and 32 kbit/s ADPCM for its voice codec. Modern PHS phone can also support many value-added services such as high speed wireless data/Internet connection (64 kbit/s and higher), WWW access, e-mailing, text messaging and even color image transfer.
VHF omnidirectional radio range (VOR), is a type of short-range radio navigation system for aircraft, enabling aircraft to determine their position and stay on course by receiving radio signals transmitted by a network of fixed ground radio beacons, with a receiver unit. It uses radio frequencies in the very high frequency (VHF) band from 108 to 117.95 MHz. Developed in the US beginning in 1937 and deployed by 1946, VOR is the standard air navigational system in the world, used by both commercial and general aviation. There are about 3000 VOR stations around the world.
A VOR ground station sends out a master signal, and a highly directional second signal that varies in phase 30 times a second compared to the master. This signal is timed so that the phase varies as the secondary antenna spins, such that when the antenna is 90 degrees from north, the signal is 90 degrees out of phase of the master. By comparing the phase of the secondary signal to the master, the angle (bearing) to the station can be determined. This bearing is then displayed in the cockpit of the aircraft, and can be used to take a fix as in earlier radio direction finding (RDF) systems, although it is, in theory,
A wireless local area network (WLAN) links two or more devices using some wireless distribution method (typically spread-spectrum or OFDM radio), and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network. Most modern WLANs are based on IEEE 802.11 standards, marketed under the Wi-Fi brand name.
Wireless LANs have become popular in the home due to ease of installation, and in commercial complexes offering wireless access to their customers; often for free. Large wireless network projects are being put up in many major cities: New York City, for instance, has begun a pilot program to provide city workers in all five boroughs of the city with wireless Internet access.
Norman Abramson, a professor at the University of Hawaii, developed the world’s first wireless computer communication network, ALOHAnet, using low-cost ham-like radios. The system included seven computers deployed over four islands to communicate with the central computer on the Oahu Island without using phone lines.
"In 1979, F.R. Gfeller and U. Bapst published a paper in the IEEE
The VHF Data Link or VHF Digital Link (VDL) is a means of sending information between aircraft and ground stations (and in the case of VDL Mode 4, other aircraft). Aeronautical VHF data links use the band 117.975 – 137 MHz assigned by the International Telecommunication Union to Aeronautical Mobile Route Services. There are ARINC standards for ACARS on VHF and other data links installed on approximately 14,000 aircraft and a range of ICAO standards defined by the Aeronautical Mobile Communications Panel (AMCP) in the 1990s. Mode 2 is the only VDL mode being implemented operationally to support Controller Pilot Data Link Communications (CPDLC).
The ICAO AMCP defined this Mode for validation purposes. It was the same as VDL Mode 2 except that it used the same VHF link as VHF ACARS so it could be implemented using analog radios before VHF Digital Radio implementation was completed. The ICAO AMCP completed validation of VDL Modes 1&2 in 1994, after which the Mode 1 was no longer needed and was deleted from the ICAO standards.
The ICAO VDL Mode 2 is the main version of VDL. It has been implemented in a Eurocontrol Link 2000+ program and is specified as the primary link in the EU Single
The Millennium Project is an independent international think tank with 40 "nodes" around the world that gathers and accesses information on futures studies that produces the annual State of the Future report since 1997 and the Futures Research Methodology series Versions 1-3.
The Project was formed by the Futures Group International, the Smithsonian Institution, the United Nations University, and the American Council for the UNU via a three year feasibility study in 1992 funded by the United States Environmental Protection Agency, United Nations Development Programme, and UNESCO. Since the beginning of operations in 1996, nearly 5,000 futurists, scholars, decision-makers, and business planners from over 50 countries have contributed with their views to the Millennium Project research.
The Project now has "Nodes" in 38 countries and 2 others are global/functional nodes: Cyber Node and the Arts/Media Node. Nodes are independent organizations (composed of both organizations and individuals from different institutional categories - government, corporations, NGOs, universities, individuals, and UN or international organizations - which acts like a transinstitution) which co-operate with
NEXRAD or Nexrad (Next-Generation Radar) is a network of 159 high-resolution S-band Doppler weather radars operated by the National Weather Service, an agency of the National Oceanic and Atmospheric Administration (NOAA) within the United States Department of Commerce. Its technical name is WSR-88D, which stands for Weather Surveillance Radar, 1988, Doppler. NEXRAD detects precipitation and atmospheric movement or wind. It returns data which when processed can be displayed in a mosaic map which shows patterns of precipitation and its movement. The radar system operates in two basic modes, selectable by the operator – a slow-scanning clear-air mode for analyzing air movements when there is little or no activity in the area, and a precipitation mode, with a faster scan for tracking active weather. NEXRAD has an increased emphasis on automation, including the use of algorithms and automated volume scans.
In the 1970s, the US Department of Commerce, Department of Defense, and the Transportation Department found the need to replace the existing national radar network, consisting of non-Doppler WSR-74 and WSR-57 radars developed in 1974 and 1957, respectively, to better serve their
Pay television, premium television, or premium channels refers to subscription-based television services, usually provided by both analog and digital cable and satellite, but also increasingly via digital terrestrial and internet television. Subscription television began in Multi-Channel Transition and transitioned into the Post Network Era. Some parts of the world, notably in France and the US, have also offered encrypted analog terrestrial signals, available for subscription.
Subscription based or pay television has resulted in a change in what type of content is broadcast by these networks. This model has led to networks creating much more specialized types of shows to influence viewers to subscribe. Subscription networks are most concerned with providing content that will make people want to subscribe as well as renew subscriptions rather than who is watching and when this viewing is taking place.
Most premium channels air movies, as well as specials, sporting events and original television series. These services are also commonly devoid of traditional commercial advertising with programs uninterrupted by television commercials, instead breaks are inserted between programs that
A Synthetic Vision System (SVS) is a computer-mediated reality system for aerial vehicles, that uses 3D to provide pilots with clear and intuitive means of understanding their flying environment.
Synthetic Vision was developed by NASA and the U.S. Air Force in the late 1970s and 1980s in support of advanced cockpit research, and in 1990s as part of the Aviation Safety Program. Development of the High Speed Transport (HST) fueled NASA research in the 1980s and 1990s. In the early 1980s, the USAF recognized the need to improve cockpit situation awareness to support piloting ever more complex aircraft, and pursued SVS (sometimes called pictorial format avionics) as an integrating technology for both manned and remotely piloted systems. NASA initiated industry involvement in early 2000 with major avionics manufacturers. Researchers like E. Theunissen at Delft University of Technology in the Netherlands contributed greatly to the development of SVS technology.
Synthetic Vision provides situational awareness to the operators by using terrain, obstacle, geo-political, hydrological and other databases. A typical SVS application uses a set of databases stored on board the aircraft, an image
The Earth Observing System (EOS) is a program of NASA comprising a series of artificial satellite missions and scientific instruments in Earth orbit designed for long-term global observations of the land surface, biosphere, atmosphere, and oceans of the Earth. The satellite component of the program was launched in 1997. The program is centerpiece of NASA's Earth Science Enterprise (ESE).
Enhanced 911, E-911 or E911 is a system used in North America that links emergency callers with the appropriate public resources. The three-digit emergency telephone number originated in the United Kingdom in 1937 and has spread to continents and countries across the globe. Other easy dial codes, including the 112 number adopted by the European Union in 1991, have been deployed to provide free-of-charge emergency calls.
In North America, where 9-1-1 was chosen as the easy access code, the system tries to automatically associate a location with the origin of the call. This location may be a physical address or other geographic reference information such as X/Y map coordinates. The caller's telephone number is used in various ways to derive a location that can be used to dispatch police, fire, emergency medical and other response resources. Automatic location of the emergency makes it quicker to locate the required resources during fires, break-ins, kidnappings, and other events where communicating one's location is difficult or impossible.
In North America the incoming 9-1-1 call is typically answered at the Public Safety Answering Point (PSAP) of the governmental agency that has
Broadband Radio Service (BRS) formerly known as Multichannel Multipoint Distribution Service (MMDS), also known as Wireless Cable, is a wireless telecommunications technology, used for general-purpose broadband networking or, more commonly, as an alternative method of cable television programming reception. MMDS is used in The United States, Canada, Mexico, Dominican Republic, Iceland, Ireland, Ukraine, Russia, Slovakia, Bolivia, Brazil, Barbados, Australia, Nigeria, Pakistan, Panama, Sri Lanka, Thailand, Uruguay, India, Belarus, Lebanon, Cambodia and Kazakhstan. It is most commonly used in sparsely populated rural areas, where laying cables is not economically viable, although some companies may also offer MMDS services in urban areas.
The BRS band uses microwave frequencies at 2.1 GHz and from 2.5 GHz to 2.7 GHz. Reception of BRS-delivered television and data signals is done with a rooftop microwave antenna. The antenna is attached to a down-converter or transceiver to receive and transmit the microwave signal and convert them to frequencies compatible with standard TV tuners (much like on satellite dishes where the signals are converted down to frequencies more compatible with
In telecommunications, 4G is the fourth generation of cell phone mobile communications standards. It is a successor of the third generation (3G) standards. A 4G system provides mobile ultra-broadband Internet access, for example to laptops with USB wireless modems, to smartphones, and to other mobile devices. Conceivable applications include amended mobile web access, IP telephony, gaming services, high-definition mobile TV, video conferencing and 3D television. Recently, Android and Windows-enabled cellular devices have fallen in the 4G category. One base advantage of 4G is that it can at any point of travelling time provide an internet data transfer rate higher than any existing cellular services (excluding broadband and Wi-Fi connections)
Two 4G candidate systems are commercially deployed: the Mobile WiMAX standard (at first in South Korea in 2006), and the first-release Long Term Evolution (LTE) standard (in Scandinavia since 2009). It has however been debated if these first-release versions should be considered as 4G or not, as the technical definition below.
In the U.S. Sprint Nextel has deployed Mobile WiMAX networks since 2008, and MetroPCS was the first operator to offer
The Wide Area Augmentation System (WAAS) is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area.
WAAS uses a network of ground-based reference stations, in North America and Hawaii, to measure small variations in the GPS satellites' signals in the western hemisphere. Measurements from the reference stations are routed to master stations, which queue the received Deviation Correction (DC) and send the correction messages to geostationary WAAS satellites in a timely manner (every 5 seconds or better). Those satellites broadcast the correction messages back to Earth, where WAAS-enabled GPS receivers use the corrections while computing their positions to improve accuracy.
The International Civil Aviation Organization (ICAO) calls this type of system a satellite-based augmentation system (SBAS). Europe and Asia are developing their own SBASs, the Indian GPS Aided Geo Augmented Navigation
Synthetic-aperture radar (SAR) is a form of radar whose defining characteristic is its use of relative motion, between an antenna and its target region, to provide distinctive long-term coherent-signal variations, that are exploited to obtain finer spatial resolution than is possible with conventional beam-scanning means. It originated as an advanced form of side-looking airborne radar (SLAR).
SAR is usually implemented by mounting, on a moving platform such as an aircraft or spacecraft, a single beam-forming antenna from which a target scene is repeatedly illuminated with pulses of radio waves at wavelengths anywhere from a meter down to millimeters. The many echo waveforms received successively at the different antenna positions are coherently detected and stored and then post-processed together to resolve elements in an image of the target region.
Current (2010) airborne systems provide resolutions to about 10 cm, ultra-wideband systems provide resolutions of a few millimeters, and experimental terahertz SAR has provided sub-millimeter resolution in the laboratory.
SAR images have wide applications in remote sensing and mapping of the surfaces of both the Earth and other
Aircell is a private company started in 1991 developing broadband for both private and commercial aviation. Aircell is the only company in the United States authorized by the Federal Communications Commission (FCC) and Federal Aviation Administration (FAA) to use frequencies in the 800 MHz band for inflight communications. Aircell successfully bid $31.3 million for a 3 MHz air-to-ground spectrum in an FCC auction in June 2006. The system is based on the TIA-856-A Evolution Data Optimized (EV-DO) standard.
Aircell holds over 20 patents relating to technology for airborne telecommunications. Formation, based in Moorestown, NJ, developed two critical hardware components of Aircell's Gogo Inflight Internet system: its Central Processor Unit (ACPU) and the custom built Cabin Wireless Access Point (CWAP).
The company states that the idea for Aircell began in a barbecue restaurant in Denison, Texas, where company founder Jimmy Ray first made sketches on a paper napkin for an affordable telephone system for airplanes. Jimmy Ray subsequently formed Aircell.
On August 1, 2007, American Airlines partnered with Aircell to offer broadband on American's flights. On September 13, 2007, Virgin
The Atacama Large Millimeter/sub-millimeter Array (ALMA) is an array of radio telescopes in the Atacama desert of northern Chile. Since a high and dry site is crucial to millimeter wavelength operations, the array is being constructed on the Chajnantor plateau at 5000 metres altitude. Consisting of 66 12-meter and 7-meter diameter radio telescopes observing at millimeter and sub-millimeter wavelengths, ALMA is expected to provide insight on star birth during the early universe and detailed imaging of local star and planet formation.
ALMA is an international partnership between Europe, the United States, Canada, East Asia and the Republic of Chile. Costing more than a billion US dollars, it is the most expensive ground-based telescope currently under construction. ALMA began scientific observations in the second half of 2011 and the first images were released to the press on 3 October 2011. The project is scheduled to be fully operational by the end of 2012.
The initial ALMA array will be composed of 66 high-precision antennas, and operate at wavelengths of 0.3 to 9.6 mm. The array will have much higher sensitivity and higher resolution than existing sub-millimeter telescopes such
A Search and Rescue Transponder (SART) is a self contained, waterproof radar transponder intended for emergency use at sea. The radar-SART is used to locate a survival craft or distressed vessel by creating a series of dots on a rescuing ship's radar display. A SART will only respond to a 9 GHz X-band (3 cm wavelength) radar. It will not be seen on S-band (10 cm) or other radar. Shipboard Global Maritime Distress Safety System (GMDSS) include one or more search and rescue locating devices. These devices may be either a radar-SART (Search and Rescue Transponder), or a GPS-based AIS-SART (Automatic Identification System Search and Rescue Transmitter).
The radar-SART may be triggered by any X-band radar within a range of approximately 8 nautical miles (15 kilometers). Each radar pulse received causes the SART to transmit a response which is swept repetitively across the complete radar frequency band. When interrogated, it first sweeps rapidly (0.4 microsecond) through the band before beginning a relatively slow sweep (7.5 microseconds) through the band back to the starting frequency. This process is repeated for a total of twelve complete cycles. At some point in each sweep, the
A microwave landing system (MLS) is an all-weather, precision landing system originally intended to replace or supplement instrument landing systems (ILS). MLS has a number of operational advantages, including a wide selection of channels to avoid interference with other nearby airports, excellent performance in all weather, a small "footprint" at the airports, and wide vertical and horizontal "capture" angles that allowed approaches from wider areas around the airport.
Although some MLS systems became operational in the 1990s, the widespread deployment initially envisioned by its designers never became a reality. GPS-based systems, notably WAAS, allowed the expectation of the same level of positioning detail with no equipment needed at the airport. GPS/WAAS dramatically lowers the cost of implementing precision landing approaches, and since its introduction most existing MLS systems in North America have been turned off. GPS/WAAS-based LPV 'Localizer Performance with Vertical guidance' approaches provide vertical guidance comparable to ILS Category I and FAA-published LPV approaches currently outnumber ILS approaches at US airports.
MLS continues to be of some interest in Europe,
Fixed Service Satellite (FSS) is the official classification (used chiefly in North America) for geostationary communications satellites used for broadcast feeds for television stations and radio stations and broadcast networks, as well as for telephony, telecommunications and data communications.
FSSs have also been used for Direct-To-Home (DTH) satellite television channels in North America since the late 1970s. This role has been mostly supplanted by direct broadcast satellite (DBS) television systems starting in 1994 when DirecTV launched the first DBS television system. However, FSSs in North America are also used to relay channels of cable TV networks from their originating studios to local cable headends and to the operations centers of DBS services (such as DirecTV and Dish Network) to be re-broadcast over their DBS systems.
FSSs were the first geosynchronous communications satellites launched in space (such as Intelsat 1 (Early Bird), Syncom 3, Anik 1, Westar 1, Satcom 1 and Ekran) and new ones are still being launched and utilized to this day.
FSSs operate in either the C band (from 3.7 to 4.2 GHz) or the FSS Ku bands (from 11.45 to 11.7 and 12.5 to 12.75 GHz in Europe,
Earth-Moon-Earth, also known as moon bounce, is a radio communications technique which relies on the propagation of radio waves from an Earth-based transmitter directed via reflection from the surface of the Moon back to an Earth-based receiver.
The use of the Moon as a passive communications satellite was proposed by Mr. W.J. Bray of the British General Post Office in 1940. It was calculated that with the available microwave transmission powers and low noise receivers, it would be possible to beam microwave signals up from Earth and reflect off the Moon. It was thought that at least one voice channel would be possible.
The "moon bounce" technique was developed by the United States Military in the years after World War II, with the first successful reception of echoes off the Moon being carried out at Fort Monmouth, New Jersey on January 10, 1946 by John H. DeWitt as part of Project Diana. The Communication Moon Relay project that followed led to more practical uses, including a teletype link between the naval base at Pearl Harbor, Hawaii and United States Navy headquarters in Washington, DC. In the days before communications satellites, a link free of the vagaries of ionospheric
The Hubble Space Telescope (HST) is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4-meter (7.9 ft) aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared. The telescope is named after the astronomer Edwin Hubble.
Hubble's orbit outside the distortion of Earth's atmosphere allows it to take extremely sharp images with almost no background light. Hubble's Ultra-Deep Field image, for instance, is the most detailed visible-light image ever made of the universe's most distant objects. Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.
Although not the first space telescope, Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy. The HST was built by the United States space agency NASA, with contributions from the European Space Agency, and is operated by the Space Telescope Science Institute. The HST is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the
In a conventional, analog two-way radio system, a standard radio has noise squelch or carrier squelch which allows a radio to receive all transmissions. Selective calling is used to address a subset of all two-way radios on a single radio frequency channel. Where more than one user is on the same channel, (co-channel users,) selective calling can address a subset of all receivers or can direct a call to a single radio. Selective calling features fit into two major categories: individual calling and group calling. Individual calls generally have longer time-constants: it takes more air-time to call an individual radio unit than to call a large group of radios.
Selective calling is akin to the use of a lock on a door. A radio with carrier squelch is unlocked and will let any signal in. Selective calling locks out all signals except ones with the correct 'key', in this case a specific digital code. Selective calling systems can overlap; a radio may have (group call) and DTMF individual calling.
Selective calling prevents you from hearing others on a shared channel. It does not eliminate interference from co-channel users (other users on the same radio channel). If another user is
Time division multiple access (TDMA) is a channel access method for shared medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel capacity. TDMA is used in the digital 2G cellular systems such as Global System for Mobile Communications (GSM), IS-136, Personal Digital Cellular (PDC) and iDEN, and in the Digital Enhanced Cordless Telecommunications (DECT) standard for portable phones. It is also used extensively in satellite systems, combat-net radio systems, and PON networks for upstream traffic from premises to the operator. For usage of Dynamic TDMA packet mode communication, see below.
TDMA is a type of Time-division multiplexing, with the special point that instead of having one transmitter connected to one receiver, there are multiple transmitters. In the case of the uplink from a mobile phone to a base station this becomes particularly difficult because the mobile phone can move
CT2 is a cordless telephony standard that was used in the early 1990s to provide short-range proto-mobile phone service in some countries in Europe. It is considered the precursor to the popular DECT system. CT2 is frequently referred to by the marketing name "Telepoint."
CT2 is a digital FDMA system that uses Time Division Duplexing technology to share carrier frequencies between handsets and base stations. Features of the system are:
Unlike DECT, CT2 was a voice-only system, though like any minimally-compressed voice system, users could deploy analog modems to transfer data. In the early nineties, Apple Computer sold a CT2 modem called the PowerBop to make use of France's Bibop CT2 network. Although CT2 is a microcellular system, fully capable of supporting handoff, unlike DECT it does not support "forward handoff", meaning that it has to drop its former radio link before establishing the subsequent one, leading to a sub-second dropout in the call during the handover.
CT2 was deployed in a number of countries, including Britain and France. In Britain, the Ferranti Phonezone system was the first public network to go live in 1989, and the much larger Rabbit network operated from
The International Space Station (ISS) is a habitable artificial satellite in low Earth orbit. It follows the Salyut, Almaz, Skylab and Mir stations as the ninth space station to be inhabited. The ISS is a modular structure whose first component was launched in 1998. Like many artificial satellites, the station can be seen from Earth without any equipment (referred to as naked eye). The ISS consists of pressurised modules, external trusses, solar arrays and other components. ISS components have been launched by American Space Shuttles as well as Russian Proton and Soyuz rockets. Budget constraints led to the merger of three space station projects with the Japanese Kibō module and Canadian robotics. In 1993 the partially built Soviet/Russian Mir-2, the proposed American Freedom, and the proposed European Columbus merged into a single multinational programme. The Russian Federal Space Agency (RSA/RKA) is using the ISS as a work site to assemble their next space station, called OPSEK. Modules and components for the new station began arriving on orbit in 2010, and the RSA plans to commission the new station before the remainder of the ISS is de-orbited.
The ISS serves as a microgravity
NAVTEX (Navigational Telex) is an international automated medium frequency direct-printing service for delivery of navigational and meteorological warnings and forecasts, as well as urgent marine safety information to ships. It was developed to provide a low-cost, simple, and automated means of receiving this information aboard ships at sea within approximately 370 km (200 nautical miles) off shore. NAVTEX stations in the U.S. are operated by the United States Coast Guard. There are no user fees associated with receiving NAVTEX broadcasts.
Where the messages contain weather forecasts, an abbreviated format very similar to the shipping forecast is used.
NAVTEX is a component of the International Maritime Organization/International Hydrographic Organization Worldwide Navigation Warning Service (WWNWS). NAVTEX is also a major element of the Global Maritime Distress Safety System (GMDSS). International Convention for the Safety of Life at Sea (SOLAS) mandated certain classes of vessels must carry NAVTEX, beginning August 1, 1993.
NAVTEX transmissions are also called narrow-band direct printing (NBDP). The transmissions are layered on top of SITOR collective B-mode. SITOR-B is a forward
A radar altimeter, radio altimeter, low range radio altimeter (LRRA) or simply RA measures altitude above the terrain presently beneath an aircraft or spacecraft. This type of altimeter provides the distance between the plane and the ground directly below it, as opposed to a barometric altimeter which provides the distance above a pre-determined datum, usually sea level.
As the name implies, radar (radio detection and ranging) is the underpinning principle of the system. Radio waves are transmitted towards the ground and the time it takes them to be reflected back and return to the aircraft is timed. Because speed, distance and time are all related to each other, the distance from the surface providing the reflection can be calculated as the speed of the radio wave and therefore the time it takes to travel a distance are known quantities.
Alternatively, Frequency Modulated Continuous-wave radar can be used. The greater the frequency shift the further the distance travelled. This method can achieve much better accuracy than the aforementioned for the same outlay and radar altimeters that use frequency modulation are industry standard.
In 1924, American engineer Lloyd Espenschied
The AN/SPQ-11 Cobra Judy is a PESA radar found on the Observation Island-class missile range instrumentation ship.
It is used for space tracking, ballistic missiles tracking and other instrumentation.
Cobra Judy is the sea component of the COBRA program for monitoring missile launches and outer space.
Dedicated short-range communications are one-way or two-way short- to medium-range wireless communication channels specifically designed for automotive use and a corresponding set of protocols and standards. In October 1999, the United States Federal Communications Commission (FCC) allocated in the USA 75MHz of spectrum in the 5.9GHz band for DSRC to be used by Intelligent Transportation Systems ITS. Also, in Europe in August 2008 the European Telecommunications Standards Institute (ETSI) has allocated 30 MHz of spectrum in the 5.9GHz band for ITS.
Currently its main use in Europe and Japan is in electronic toll collection. DSRC systems in Europe, Japan and U.S. are not, at present, compatible.
Other possible applications are:
Other short range wireless protocols are IEEE 802.11, Bluetooth and CALM.
In the European standardization organisation CEN, sometimes in co-operation with the International Organization for Standardization (ISO) the following DSRC standards have been developed:
Each standard addresses different layers in the OSI model communication stack.
Short Range Agent Communications (SRAC) was also adopted by Western intelligence agencies during the Cold War yet in the
The Educational Broadband Service (EBS) was formerly known as the Instructional Television Fixed Service (ITFS). ITFS was a band of twenty (20) microwave channels available to be licensed by the U.S. Federal Communications Commission (FCC) to local credit granting educational institutions. It was designed to serve as a means for educational institutions to deliver live or pre-recorded Instructional television to multiple sites within school districts and to higher education branch campuses. In recognition of the variety and quantity of video materials required to support instruction at numerous grade levels and in a range of subjects, licensees were typically granted a group of four channels. Its low capital and operating costs as compared to broadcast television, technical quality that compared favorably with broadcast television, and its multi-channel per licensees feature made ITFS an extremely cost effective vehicle for the delivery of Educational television materials.
The FCC changed the name of this service to the Educational Broadband Service (EBS) and changed the allocation so each licensee would not have four 6 MHz wide channels but instead would have one 6 MHz channel and
Teledesic was a company founded in the 1990s to build a commercial broadband satellite constellation for Internet services. Using low-earth orbiting satellites small antennas could be used to provide uplinks of as much as 100 Mbit/second and downlinks of up to 720 Mbit/second. The original 1995 proposal was extremely ambitious, costing over US$9 billion and originally planning 840 active satellites with in-orbit spares at an altitude of 700 km. In 1997 the scheme was scaled back to 288 active satellites at 1400 km and was later scaled back further in complexity and number of satellites as the projected market demand continued to decrease.
The commercial failure of the similar Iridium and Globalstar ventures (composed of 66 and 48 operational satellites, respectively) and other systems, along with bankruptcy protection filings, were primary factors in halting the project, and Teledesic officially suspended its satellite construction work on October 1, 2002.
Teledesic was notable for gaining early funding from Microsoft (investing US$30 million for an 8.5% stake), Craig McCaw, Bill Gates, Paul Allen, and Saudi prince Alwaleed bin Talal, and for achieving allocation on the Ka-band
Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing cdmaOne technology. UMTS uses Wideband Code Division Multiple Access (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators.
UMTS specifies a complete network system which uses, covering the radio access network (UMTS Terrestrial Radio Access Network, or UTRAN), the core network (Mobile Application Part, or MAP) and the authentication of users via SIM cards (Subscriber Identity Module).
The technology described in UMTS is sometimes also referred to as Freedom of Mobile Multimedia Access (FOMA) or 3GSM.
Unlike EDGE (IMT Single-Carrier, based on GSM) and CDMA2000 (IMT Multi-Carrier), UMTS requires new base stations and new frequency allocations.
UMTS supports maximum theoretical data transfer rates of 42 Mbit/s when HSPA+ is implemented in the network.
Inmarsat-4 F3 is a communications satellite operated by the British satellite operator Inmarsat. It was launched into a geosynchronous orbit at 22:43 GMT on 18 August 2008, by a Proton-M/Briz-M Enhanced carrier rocket. It is currently located at 98° West of the Greenwich Meridian, providing coverage of the Americas. It entered service on 7 January 2009.
Like the earlier Inmarsat-4 F1 and F2 satellites, Inmarsat-4 F3 was constructed by EADS Astrium, using a Eurostar E3000 bus. It has a mass of 5,960 kilograms, and is expected to operate for 13 years. It was originally slated for launch using an Atlas V 531, but was transferred to Proton due to a large backlog of Atlas launches.
Bell Laboratories Layered Space-Time (BLAST) is a transceiver architecture for offering spatial multiplexing over multiple-antenna wireless communication systems. Such systems have multiple antennas at both the transmitter and the receiver in an effort to exploit the many different paths between the two in a highly-scattering wireless environment. BLAST was developed by Gerard Foschini at Lucent Technologies' Bell Laboratories (now Alcatel-Lucent Bell Labs). By careful allocation of the data to be transmitted to the transmitting antennas, multiple data streams can be transmitted simultaneously within a single frequency band — the data capacity of the system then grows directly in line with the number of antennas (subject to certain assumptions). This represents a significant advance on current, single-antenna systems.
V-BLAST (Vertical-Bell Laboratories Layered Space-Time) is a detection algorithm to the receipt of multi-antenna MIMO systems. Available for the first time in 1996 at Bell Laboratories in New Jersey in the United States by Gerard J. Foschini. He proceeded simply to eliminate interference caused successively issuers.
Its principle is quite simple: to make a first
Meteor burst communications (MBC), also referred to as meteor scatter communications, is a radio propagation mode that exploits the ionized trails of meteors during atmospheric entry to establish brief communications paths between radio stations up to 2,250 kilometres (1,400 mi) apart.
As the earth moves along its orbital path, billions of particles known as meteors enter the earth's atmosphere every day; a small fraction of which have properties useful for point to point communication. When these meteors begin to burn up, they create a trail of ionized particles in the E layer of the atmosphere that can persist for up to several seconds. The ionization trails can be very dense and thus used to reflect radio waves. The frequencies that can be reflected by any particular ion trail are determined by the intensity of the ionization created by the meteor, often a function of the initial size of the particle, and are generally between 30 MHz and 50 MHz.
The distance over which communications can be established is determined by the altitude at which the ionization is created, the location over the surface of the Earth where the meteor is falling, the angle of entry into the atmosphere,
An airport surveillance radar (ASR) is a radar system used at airports to detect and display the position of aircraft in the terminal area.
The Digital Airport Surveillance Radar (DASR) is a new terminal air traffic control radar system that replaces current analog systems with new digital technology. The United States Air Force Electronics Systems Center, the US Federal Aviation Administration, US Army and the US Navy are in the process of procuring DASR systems to upgrade existing radar facilities for US Department of Defense (DoD) and civilian airfields. The DASR system detects aircraft position and weather conditions in the vicinity of civilian and military airfields. The civilian nomenclature for this radar is the ASR-11. The ASR-11 will replace existing ASR-7, ASR-8, and ASR-9 models. The military nomenclature for the radar is the AN/GPN-30. The older radars, some up to 20 years old, are being replaced to improve reliability, provide additional weather data, reduce maintenance cost, improve performance, and provide digital data to new digital automation systems for presentation on air traffic controller displays. The Iraqi Air Force has received the DASR system.
ASR data is
Mobile Satellite Service (MSS) is a satellite system which uses portable terrestrial terminals. MSS terminals may be mounted on a ship, an airplane, or an automobile. MSS terminals may even be carried by an individual.
The most promising application of Mobile Satellite Service is portable satellite telephones which will enable phone service anywhere on the globe.
In the last few years MSS was one of the fast grwoing services, due to the simplisity and cost of the services. The coomen thinking would be to posisioned MSS in area where there is not any cellular coverage, but in fact the varity of soultions is provided also in places that are well covered by mobile services.
MSS is an essential communications services to and from remote areas where no other form of communication is available. Whether at sea, on land or in flight, this service ideally suit the Maritime, Aviation, Government/Military, emergency/humanitarian services, mining, forestry, oil and gas, heavy equipment, transportation and utilities industries.
From the South American rain forests to the African Savanna, from the waters of the Pacific Ocean to the sand seas of the Sahara, mobile satellite services keep
IS-54 and IS-136 are second-generation (2G) mobile phone systems, known as Digital AMPS (D-AMPS). It was once prevalent throughout the Americas, particularly in the United States and Canada in the 1990's. D-AMPS is considered end-of-life, and existing networks have mostly been replaced by GSM/GPRS or CDMA2000 technologies.
This system is most often referred to as TDMA. That name is based on the abbreviation for time division multiple access, a common multiple access technique which is used by multiple protocols, including GSM, as well as in IS-54 and IS-136. However, D-AMPS has been competing against GSM and systems based on code division multiple access (CDMA) for adoption by the network carriers, although it is now being phased out in favor of GSM/GPRS and CDMA2000 technology.
D-AMPS uses existing AMPS channels and allows for smooth transition between digital and analog systems in the same area. Capacity was increased over the preceding analog design by dividing each 30 kHz channel pair into three time slots (hence time division) and digitally compressing the voice data, yielding three times the call capacity in a single cell. A digital system also made calls more secure because
A multichannel video programming distributor (MVPD) is a service provider delivering video programming services, usually for a subscription fee (pay TV). These operators include cable television (CATV) systems, direct-broadcast satellite (DBS) providers, and wireline video providers including Verizon FiOS as well as AT&T U-verse and competitive local exchange carriers (CLECs) using IPTV.
Section 602 (13) of The Communications Act of 1934 (as amended by the Telecommunications Act of 1996) defines an MVPD as
a person such as, but not limited to, a cable operator, a multichannel multipoint distribution service, a direct broadcast satellite service, or a television receive-only satellite program distributor, who makes available for purchase, by subscribers or customers, multiple channels of video programming.
In 1992, nearly all MVPD customers had cable. By 2012, satellite dishes had 30 percent of the market.
On January 7, 2009, independent U.S. Senator Bernie Sanders of Vermont introduced the Digital TV Transition Fairness Act. He introduced the idea in a September 19, 2008, letter to Federal Communications Commission chairman Kevin Martin which stated, in part, "Americans should not
A racon is a radar transponder commonly used to mark maritime navigational hazards. The word is a portmanteau of RAdar and beaCON.
When a racon receives a radar pulse, it responds with a signal on the same frequency which puts an image on the radar display. This takes the form of a short line of dots and dashes forming a Morse character radiating away from the location of the beacon on the normal plan position indicator radar display. The length of the line usually corresponds to the equivalent of a few nautical miles on the display.
Within the United States, the United States Coast Guard operates about 80 racons, and other organisations also operate them, for example the owners of oil platforms. Their use for purposes other than aids to navigation is prohibited, and they are used to mark:
In other parts of the World they are also used to indicate:
Their characteristics are defined in the ITU-R Recommendation M.824, Technical Parameters of Radar Beacons (RACONS). Racons usually operate on the 9320 MHz to 9500 MHz marine radar band (X-band), and most also operate on the 2920 MHz to 3100 MHz marine radar band (S-band). Modern racons are frequency-agile; they have a wide-band receiver
NASA's Space Shuttle program, officially called Space Transportation System (STS), was the United States government's manned launch vehicle program from 1981 to 2011. The winged Space Shuttle orbiter was launched vertically, usually carrying four to seven astronauts (although eight have been carried) and up to 50,000 lb (22,700 kg) of payload into low Earth orbit (LEO). When its mission was complete, the Shuttle could independently move itself out of orbit using its Maneuvering System (it oriented itself appropriately and fired its main OMS engines, thus slowing it down) and re-enter the Earth's atmosphere. During descent and landing the orbiter acted as a re-entry vehicle and a glider, using its OMS system and flight surfaces to make adjustments.
The Shuttle is the only winged manned spacecraft to have achieved orbit and land, and the only reusable space vehicle that has ever made multiple flights into orbit (though winged, the Russian shuttle Buran made only one unmanned spaceflight). Its missions involved carrying large payloads to various orbits (including segments to be added to the International Space Station), provided crew rotation for the International Space Station, and
The SPACEWAY system was originally envisioned as a global Ka band communications system by Hughes Electronics. When the project to build the system was taken over by Hughes Network Systems, a subsidiary of Hughes Electronics, it was transformed into a phased deployment initially only launching a North American satellite system. This is in comparison to other more ambitious systems such as Teledesic and Astrolink which retained their full global nature and which subsequently failed to complete their systems. Hughes Network Systems working with Hughes Electronics subsidiary Hughes Space and Communications (and subsequently sold to Boeing and called Boeing Satellite Systems and later the Boeing Satellite Development Center) completed and built the North American SPACEWAY system meant to provide broadband capabilities of up to 512 kbit/s, 2 Mbit/s, and 16 Mbit/s uplink data communication rates with fixed Ka-band satellite terminal antennas sized as small as 74 cm (29 in). The broadband SPACEWAY system was standardized by Telecommunications Industry Association and European Telecommunications Standards Institute as the Regenerative Satellite Mesh - A Air Interface.
After News Corp
A private cable operator (also known as PCO) is a private small independent cable company competing directly with Multi system operators (MSO). PCOs typically offer services to multi-family dwellings, gated communities, hotels and other small businesses. In some small municipalities in the city may be a PCO.
In some cases PCOs offer voice, wireless and data services as well. The U.S. Federal Communications Commission (FCC) currently has rules regarding the exclusive contracts that used to be granted to cable providers.
Amateur radio (also called ham radio) is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication. The term "amateur" is used to specify persons interested in radio technique solely with a personal aim and without direct pecuniary interest, and to differentiate it from commercial broadcasting, public safety (such as police and fire), or professional two-way radio services (such as maritime, aviation, taxis, etc.).
The amateur radio service (amateur service and amateur satellite service) is established by the International Telecommunication Union (ITU) through the International Telecommunication Regulations. National governments regulate technical and operational characteristics of transmissions and issue individual stations licenses with an identifying call sign. Prospective amateur operators are tested for their understanding of key concepts in electronics and the host government's radio regulations. Radio amateurs use a variety of voice, text, image, and data communications modes and have access to frequency allocations throughout the RF spectrum to
The Arecibo Observatory is a radio telescope in the mailing area of the city of Arecibo, Puerto Rico. This observatory is operated by the company SRI International under cooperative agreement with the National Science Foundation. This observatory is also called the National Astronomy and Ionosphere Center, although "NAIC" refers to both the observatory and the staff that operates it.
The 305 m (1,000 ft) radio telescope here is the world's largest single-aperture telescope. It is used in three major areas of research: radio astronomy, aeronomy, and radar astronomy observations of the larger objects of the Solar System. Scientists who want to use the telescope submit proposals, and these are evaluated by an independent scientific board.
Since it is visually distinctive, this telescope has made notable appearances in motion picture and television productions. The telescope received additional recognition in 1999 when it began to collect data for the SETI@home project.
This radio telescope has been listed on the American National Register of Historic Places beginning in 2008. It was the featured listing in the National Park Service's weekly list of October 3, 2008. The center was
Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances (using short-wavelength radio transmissions in the ISM band from 2400–2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with high levels of security. Created by telecoms vendor Ericsson in 1994, it was originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices, overcoming problems of synchronization.
Bluetooth is managed by the Bluetooth Special Interest Group, which has more than 17,000 member companies in the areas of telecommunication, computing, networking, and consumer electronics. The SIG oversees the development of the specification, manages the qualification program, and protects the trademarks. To be marketed as a Bluetooth device, it must be qualified to standards defined by the SIG. A network of patents is required to implement the technology and are licensed only for those qualifying devices.
The word "Bluetooth" is an anglicised version of the Scandinavian Blåtand/Blåtann, the epithet of the tenth-century king Harald I of Denmark and parts of Norway who united dissonant Danish tribes into a single
The Defense Satellite Communications System (DSCS) provides the United States with military communications to support globally distributed military users. DSCS will be replaced by the Wideband Global SATCOM system. A total of 14 DSCS III satellites were launched between the early 1980s and 2003. Two satellites were launched aboard the Space Shuttle Atlantis in 1985 during STS-51J. According to the USAF, in early 2008 most of the satellites were still working.
DSCS went though three major phases. Since the first launch, DSCS has been the "workhorse" of military satellite communications. DSCS III satellites currently exceed their 10-year design life.
DSCS II provided secure voice and data communications for the U.S. military. The program was managed by the Defense Communications Agency (DCA), now the Defense Information Systems Agency.
The space vehicles were spin stabilized with a de-spun antenna platform. The body was mounted with solar cells which produced 535 watts. Three NiCd batteries provided electrical power and it was supported by a hydrazine propulsion subsystem.
The communications payload included two 20-watt X-band channels. The transponders were supported by steerable
Dish Network Corporation (NASDAQ: DISH), commonly known as DISH, is a United States satellite broadcaster, providing direct broadcast satellite service—including satellite television, audio programming, and interactive television services—to 14.337 million commercial and residential customers in the United States. Dish Network has approximately 24,500 employees, most of whom are located within the U.S. The corporate office is based in Meridian, an unincorporated area of Douglas County, Colorado.
EchoStar Satellite L.L.C. was founded by Charlie Ergen, his wife Candy and their friend Jim DeFranco as a satellite television equipment distributor in 1980. EchoStar was officially re-branded as Dish Network in March 1996. This branding came after the successful launch of its first satellite, EchoStar I in December 1995 and marked the beginning of the company offering subscription television services. The company has since launched numerous satellites, with 14 owned and leased satellites currently in its fleet.
As of January 2008, Dish Network split from EchoStar, with each entity becoming a separate company. EchoStar is the key technology partner to Dish Network, which focuses only on
Globalstar is a low Earth orbit (LEO) satellite constellation for satellite phone and low-speed data communications, somewhat similar to the Iridium satellite constellation and Orbcomm satellite systems.
The Globalstar project was launched in 1991 as a joint venture of Loral Corporation and Qualcomm. On March 24, 1994, the two sponsors announced formation of Globalstar LP, a limited partnership established in the U.S., with financial participation from eight other companies, including Alcatel, AirTouch, Deutsche Aerospace, Hyundai and Vodafone. At that time, the company predicted the system would launch in 1998, based on an investment of $1.8 billion.
Globalstar received its US spectrum allocation from the FCC in January 1995, and continued to negotiate with other nations for rights to use the same radio frequencies in their countries.
The first satellites were launched in February 1998, but system deployment was delayed due to a launch failure in September 1998 that resulted in the loss of 12 satellites in a launch by the Russian Space Agency. In February 2000, it launched the last of 52 satellites — 48 satellites and four in-orbit spares (reduced from the original plan of eight
Personal communications network (PCN) is the European digital cellular mobile telephone network, developed in accordance with GSM standards.
The PCN system was first initiated by Lord Young, UK Secretary of State for Trade and Industry, in 1988. The main characteristics of PCN are as follows:
PCN uses the DCS-1800 systems, which is similar to GSM, but up converts the frequency to 1.7–1.88 GHz, therefore the network structure, the signal structure and the transmission characteristics are similar between PCN and GSM, but operational frequencies are different.
The search for extraterrestrial intelligence (SETI) is the collective name for a number of activities people undertake to search for intelligent extraterrestrial life. Some of the most well known projects are run by Harvard University, the University of California, Berkeley and the SETI Institute. SETI projects use scientific methods to search for intelligent life on other planets. For example, electromagnetic radiation is monitored for signs of transmissions from civilizations on other worlds. The United States government contributed to early SETI projects, but recent work has been primarily funded by private sources.
There are great challenges in searching across the cosmos for a first transmission that could be characterized as intelligent, since its direction, spectrum and method of communication are all unknown beforehand. SETI projects necessarily make assumptions to narrow the search, the foremost being that electromagnetic radiation would be a medium of communication for advanced extraterrestrial life.
Many radio frequencies penetrate our atmosphere quite well, and this led to radio telescopes that investigate the cosmos using large radio antennas. Furthermore, human
TV Martí was created by the US government to provide news and current affairs programming to Cuba. It is named after Cuban independence leader José Martí, and is the television equivalent to Radio Marti.
It began broadcasting on March 27, 1990. Currently TV Martí is an element of the International Broadcasting Bureau (IBB) with its complement Radio Martí. The sister elements of TV Martí in the IBB are Voice of America (VoA), Radio Sawa, Radio Free Europe/Radio Liberty (RFE/RL), and Radio Free Asia. The IBB and the Broadcasting Board of Governors are independent federal entities spun off from the now defunct U.S. Information Agency.
The studios are currently located in Miami.
TV Martí broadcasts daily programs in Spanish via a transmitter affixed to an aerostat balloon located 10,000 feet (3,048 m) above Cudjoe Key, Florida. As a result of Hurricane Dennis, the broadcasting aerostat (which the locals named "Fat Albert") was destroyed by wind.
The Cuban government has insisted the penetration of their airwaves violates international law. This claim has not been elucidated; however, Cuba responds to these broadcasts by jamming the signals.
National Public Radio's On the Media has
A very small aperture terminal (VSAT), is a two-way satellite ground station or a stabilized maritime Vsat antenna with a dish antenna that is smaller than 3 meters. The majority of VSAT antennas range frop 75 cm to 1.2 m. Data rates typically range from 56 kbit/s up to 4 Mbit/s. VSATs access satellite(s) in geosynchronous orbit to relay data from small remote earth stations (terminals) to other terminals (in mesh topology) or master earth station "hubs" (in star topology).
VSATs are most commonly used to transmit narrowband data (point of sale transactions such as credit card, polling or RFID data; or SCADA), or broadband data (for the provision of satellite Internet access to remote locations, VoIP or video). VSATs are also used for transportable, on-the-move (utilising phased array antennas) or mobile maritime communications.
The concept of the geostationary orbit was originated by Russian theorist Konstantin Tsiolkovsky, who wrote articles on space travel at the turn of the century. In the 1920s, Hermann Oberth and Herman Potocnik, aka Herman Noordung described an orbit at an altitude of 35,900 kilometers whose period exactly matched the Earth's rotational period, making it
Automatic dependent surveillance-broadcast (ADS-B) is a surveillance technology for tracking aircraft as part of the Next Generation Air Transportation System (NextGen). The United States will require the majority of aircraft operating within its airspace to be equipped with some form of ADS-B Out by January 1, 2020.
ADS-B, which consists of two different services, "ADS-B Out" and "ADS-B In", will be replacing radar as the primary surveillance method for controlling aircraft worldwide. In the United States, ADS-B is an integral component of the NextGen national airspace strategy for upgrading/enhancing aviation infrastructure and operations. The ADS-B system can also provide traffic and government generated graphical weather information through TIS-B and FIS-B applications. ADS-B enhances safety by making an aircraft visible, realtime, to ATC and to other appropriately equipped ADS-B aircraft with position and velocity data transmitted every second. ADS-B data can be recorded and downloaded for post-flight analysis. ADS-B also provides the data infrastructure for inexpensive flight tracking, planning, and dispatch.
The system relies on two avionics components—a high-integrity
ECHELON is a name used in global media and in popular culture to describe a signals intelligence (SIGINT) collection and analysis network operated on behalf of the five signatory states to the UKUSA Security Agreement (Australia, Canada, New Zealand, the United Kingdom, and the United States, referred to by a number of abbreviations, including AUSCANNZUKUS and Five Eyes). It has also been described as the only software system which controls the download and dissemination of the intercept of commercial satellite trunk communications.
ECHELON was reportedly created to monitor the military and diplomatic communications of the Soviet Union and its Eastern Bloc allies during the Cold War in the early 1960s.
The system has been reported in a number of public sources. Its capabilities and political implications were investigated by a committee of the European Parliament during 2000 and 2001 with a report published in 2001, and by author James Bamford in his books on the National Security Agency of the United States. The European Parliament stated in its report that the term ECHELON is used in a number of contexts, but that the evidence presented indicates that it was the name for a
A software-defined radio system, or SDR, is a radio communication system where components that have been typically implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system. While the concept of SDR is not new, the rapidly evolving capabilities of digital electronics render practical many processes which used to be only theoretically possible.
A basic SDR system may consist of a personal computer equipped with a sound card, or other analog-to-digital converter, preceded by some form of RF front end. Significant amounts of signal processing are handed over to the general-purpose processor, rather than being done in special-purpose hardware. Such a design produces a radio which can receive and transmit widely different radio protocols (sometimes referred to as waveforms) based solely on the software used.
Software radios have significant utility for the military and cell phone services, both of which must serve a wide variety of changing radio protocols in real time.
In the long term, software-defined radios are expected by proponents like the SDRForum
A tactical air navigation system, commonly referred to by the acronym TACAN, is a navigation system used by military aircraft. It provides the user with bearing and distance (slant-range) to a ground or ship-borne station. It is a more accurate version of the VOR/DME system that provides bearing and range information for civil aviation. The DME portion of the TACAN system is available for civil use; at VORTAC facilities where a VOR is combined with a TACAN, civil aircraft can receive VOR/DME readings. Aircraft equipped with TACAN avionics can use this system for enroute navigation as well as non-precision approaches to landing fields. The space shuttle is one such vehicle that was designed to use TACAN navigation (although it has since been upgraded with GPS as a replacement).
The typical TACAN onboard user panel has control switches for setting the channel (corresponding to the desired surface station's assigned frequency), the operation mode for either Transmit/Receive (T/R, to get both bearing and range) or Receive Only (REC, to get bearing but not range). Capability was later upgraded to include an Air-to-Air mode (A/A) where two airborne users can get relative slant-range
A studio-transmitter link (or STL) sends a radio station's or television station's audio and video from the broadcast studio to a radio transmitter or television transmitter in another location.
This is often necessary because the best locations for an antenna are on top of a mountain, where a much shorter tower is required, but where a studio is completely impractical. Even in flat regions, the center of the station's allowed coverage area may not be near the studio location or within a populated area where a transmitter would be frowned upon by the community, so the antenna must be placed several miles or kilometres away.
Depending on the locations that must be connected, a station may choose either a point to point (PTP) link on another special radio frequency, or a newer all-digital wired link via a dedicated T1 or E1 (or larger-capacity) line. Radio links can also be digital, or the older analog type, or a hybrid of the two. Even on older all-analog systems, multiple audio and data channels can be sent using subcarriers.
Stations that employ an STL usually also have a transmitter-studio link (or TSL) to return telemetry information. Both the STL and TSL are considered
A HAPS (High-Altitude Platform System or High Altitude Pseudo-Satellite), is an unmanned aerial vehicle (UAV) which is to remain relatively stationary at high altitude.
They can be used as communications platforms, for weather surveys, traffic reports etc. Because of their relative short distance from earth compared to satellites (20 km compared to up to 40,000 km) they could even be used to provide mobile telecommunication, without the need for ground based antennas, and without the long delays associated with satellite communication.
Low-power broadcasting is electronic broadcasting at very low power and low cost, to a small community area.
The terms "low-power broadcasting" and "micropower broadcasting" (more commonly "microbroadcasting") should not be used interchangeably, because the markets are not the same. The former term is more often used to describe stations who have applied for and received official licenses. The relationship between broadcasting power and signal range is a function of many things, such as the frequency band it uses e.g., Medium Wave, Shortwave or FM, the topography of the geographical area in which it operates (mountainous or flat), atmospheric conditions, and finally the amount of radio frequency energy it transmits. As a general rule, the more energy a station transmits, the further its signal goes.
LPFM, LPAM, and LPTV are in various levels of use across the world, varying widely based on the laws and their enforcement.
Low Power FM, or LPFM is a form of FM Broadcasting that uses a low amount of energy to broadcast a signal that does not travel very far. FM, or frequency modulation radio is often transmitted on a higher frequency than AM radio. Because of the low power usage and
National missile defense (NMD) is a generic term for a type of missile defense intended to shield an entire country against incoming missiles, such as intercontinental ballistic missile (ICBMs) or other ballistic missiles.
This is also used to refer to the American nationwide antimissile program the United States has had in development since the 1990s. After the renaming in 2002, the term now refers to the entire program, not just the ground-based interceptors and associated facilities. This article focuses mainly on this system and a brief history of earlier systems which led to it.
Other elements yet to be integrated into NMD may include anti-ballistic missiles, or sea-based, space-based, laser, and high altitude missile systems. The NMD program is limited in scope and designed to counter a relatively small ICBM attack from a less sophisticated adversary. Unlike the earlier Strategic Defense Initiative program, it is not designed to be a robust shield against a large attack from a technically sophisticated adversary.
The term "national missile defense" has several meanings:
The role of defense against nuclear missiles has been a heated military and political topic for several
A satellite telephone, satellite phone, or satphone is a type of mobile phone that connects to orbiting satellites instead of terrestrial cell sites. They provide similar functionality to terrestrial mobile telephones; voice, short messaging service and low-bandwidth internet access are supported through most systems.
Depending on the architecture of a particular system, coverage may include the entire Earth, or only specific regions.
The mobile equipment, also known as a terminal, varies widely. Early satellite phone handsets had a size and weight comparable to that of a late-1980s or early-1990s mobile phone, but usually with a large retractable antenna. More recent satellite phones are similar in size to a regular mobile phone while some prototype satellite phones have no distinguishable difference from an ordinary smartphone. Satphones are popular on expeditions into remote areas where terrestrial cellular service is unavailable.
A fixed installation, such as one used aboard a ship, may include large, rugged, rack-mounted electronics, and a steerable microwave antenna on the mast that automatically tracks the overhead satellites. Smaller installations using VoIP over a two-way
A competitive local exchange carrier (CLEC), in the United States, is a telecommunications provider company (sometimes called a "carrier") competing with other, already established carriers (generally the incumbent local exchange carrier (ILEC)).
Local exchange carriers (LECs) are divided into incumbent (ILECs) and competitive (CLECs). The ILECs are usually the original, monopoly LEC in a given area, and receive different regulatory treatment from the newer CLECs. A data local exchange carrier (DLEC) is a CLEC specializing in DSL services by leasing lines from the ILEC and reselling them to Internet service providers (ISPs).
CLECs evolved from the competitive access providers (CAPs) that began to offer private line and special access services in competition with the ILECs beginning in 1985. The CAPs (such as Teleport Communications Group (TCG) and Metropolitan Fiber Systems (MFS)) deployed fiber optic systems in the central business districts of the largest US cities (New York, Chicago, Boston, etc.). A number of state public utilities commissions, particularly New York, Illinois, and Massachusetts, encouraged this competition. By the early 1990s, the CAPs began to install switches
Ultra-wideband (also known as UWB, ultra-wide band and ultraband) is a radio technology pioneered by Robert A. Scholtz and others which may be used at a very low energy level for short-range, high-bandwidth communications using a large portion of the radio spectrum. UWB has traditional applications in non-cooperative radar imaging. Most recent applications target sensor data collection, precision locating and tracking applications.
Similar to spread spectrum, UWB communications transmit in a way which does not interfere with conventional narrowband and carrier wave uses in the same frequency band. Unlike spread spectrum, however, ultra-wideband does not employ frequency-hopping (FHSS).
Ultra-wideband is a technology for transmitting information spread over a large bandwidth (>500 MHz); this should, in theory and under the right circumstances, be able to share spectrum with other users. Regulatory settings by the Federal Communications Commission (FCC) in the United States intend to provide an efficient use of radio bandwidth while enabling high-data-rate personal area network (PAN) wireless connectivity; longer-range, low-data-rate applications; and radar and imaging systems.
International Mobile Telecommunications-2000 (IMT-2000) is the global standard for third generation (3G) wireless communications as defined by the International Telecommunication Union. In 1999 ITU approved five radio interfaces for IMT-2000 as a part of the ITU-R M.1457 Recommendation:
On 18 October 2007 The ITU Radiocommunication Assembly took a decision to include WiMAX-derived technology in the framework of the IMT-2000 set of standards as the sixth element:
The Defense Support Program (DSP) is a program of the U.S. Air Force that operates the reconnaissance satellites which form the principal component of the Satellite Early Warning System currently used by the United States.
DSP satellites, which are operated by the Air Force Space Command, detect missile or spacecraft launches and nuclear explosions using sensors that detect the infrared emissions from these intense sources of heat. During Desert Storm, for example, DSP was able to detect the launches of Iraqi Scud missiles and provide timely warnings to civilians and military forces in Israel and Saudi Arabia.
The satellites are in geostationary orbits, and are equipped with infrared sensors operating through a wide-angle Schmidt camera. The entire satellite spins so that the linear sensor array in the focal plane scans over the earth six times every minute.
Typically, DSP satellites were launched on Titan IVB boosters with Inertial Upper Stages. However, one DSP satellite was launched using the Space Shuttle Atlantis on mission STS-44 (November 24, 1991).
The last one (flight 23) was launched in 2007 aboard the first operational flight of the Delta IV Heavy rocket, as the Titan IV
The Global Positioning System (GPS) is a space-based satellite navigation system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites. It is maintained by the United States government and is freely accessible to anyone with a GPS receiver.
The GPS program provides critical capabilities to military, civil and commercial users around the world. In addition, GPS is the backbone for modernizing the global air traffic system.
The GPS project was developed in 1973 to overcome the limitations of previous navigation systems, integrating ideas from several predecessors, including a number of classified engineering design studies from the 1960s. GPS was created and realized by the U.S. Department of Defense (DoD) and was originally run with 24 satellites. It became fully operational in 1994.
Advances in technology and new demands on the existing system have now led to efforts to modernize the GPS system and implement the next generation of GPS III satellites and Next Generation Operational Control System (OCX). Announcements from the Vice President and the White House in 1998
A Home Node B, or HNB, is the 3GPP's term for a 3G femtocell.
A Node B is an element of a 3G macro Radio Access Network, or RAN. A femtocell performs many of the function of a Node B, but is optimized for deployment in the home.
The following 3GPP documents are currently available:
Within an HNB Access Network there are three new network elements: the Home Node B (or femtocell), the Security Gateway (SeGW) and the Home Node B Gateway, or HNB-GW.
Between the HNB and the HNB-GW is a new interface known as Iu-h.
Home Node B (HNB) – Connected to an existing residential broadband service, an HNB provides 3G radio coverage for 3G handsets within a home. HNBs incorporate the capabilities of a standard Node B as well as the radio resource management functions of a standard Radio Network Controller RNC.
Home eNode B (HeNB) - Connected to an existing residential broadband service, an HeNB provides LTE radio coverage for LTE handsets within a home. HeNBs incorporate the capabilities of a standard eNodeB.
Security Gateway (SeGW) - Installed in an operator’s network, the Security Gateway establishes IPsec tunnels with HNBs using IKEv2 signaling for IPsec tunnel management. IPsec tunnels are
Inmarsat plc (LSE: ISAT) is a British satellite telecommunications company, offering global, mobile services. It provides telephony and data services to users worldwide, via portable or mobile terminals which communicate to ground stations through eleven geostationary telecommunications satellites. Inmarsat's network provides communications services to a range of governments, aid agencies, media outlets and businesses with a need to communicate in remote regions or where there is no reliable terrestrial network. The company is listed on the London Stock Exchange and is a constituent of the FTSE 250 Index as of December 2011.
The company was originally founded in 1979 as the International Maritime Satellite Organization (Inmarsat), a not-for-profit international organization, set up at the behest of the International Maritime Organization (IMO), a UN body, for the purpose of establishing a satellite communications network for the maritime community. It began trading in 1982. From the beginning, the acronym "Inmarsat" was used. The intent was to create a self-financing body which would improve safety of life at sea. The name was changed to "International Mobile Satellite
The Submillimeter Wave Astronomy Satellite (SWAS) was an astronomical observatory launched on December 5, 1998 as part of the Small Explorer program within NASA. Investigators at Smithsonian Astrophysical Observatory and Goddard Space Flight Center designed the telescope and the spacecraft, respectively.
The satellite examined microwaves from 487–556 GHz that originated in water molecules, molecular oxygen, atomic carbon, and carbon monoxide in space. This corresponds to wavelengths of about 0.54 to 0.61 millimeters (540 to 610 μm).
SWAS made observations until July 21, 2004. In June 2005, the spacecraft was reactivated for a 3 month period (after a year of stand-by operation) in order to observe the effects of the Deep Impact probe's collision with comet P/Tempel 1.
The main optic of SWAS is a 55 cm x 71 cm elliptical off-axis Cassegrain telescope, sending light into a pair of Schottky diode receivers.
SWAS observed a unique area of the spectrum alternately described as submillimeter (for the wavelength of light seen), microwave, radio, and/or far infrared.
Standard-definition television (SDTV) is a television system that uses a resolution that is not considered to be either high-definition television (HDTV 720p and 1080p) or enhanced-definition television (EDTV 480p). The two common SDTV signal types are 576i, with 576 interlaced lines of resolution, derived from the European-developed PAL and SECAM systems; and 480i based on the American National Television System Committee NTSC system.
In the US, digital SDTV is broadcast in the same 4:3 aspect ratio as NTSC signals. However, in other parts of the world that used the PAL or SECAM analog standards, standard-definition television is now usually shown with a 16:9 aspect ratio, with the transition occurring between the mid-1990s and mid-2000s. Older programs with a 4:3 aspect ratio are shown in 4:3.
Standards that support digital SDTV broadcast include DVB, ATSC and ISDB. The last two were originally developed for HDTV, but are more often used for their ability to deliver multiple SD video and audio streams via multiplexing, than for using the entire bitstream for one HD channel.
In ATSC Standards, SDTV can be broadcast in 720 pixels × 480 lines with 16:9 aspect ratio (40:33
An automated highway system (AHS) or Smart Road is a proposed intelligent transportation system technology designed to provide for driverless cars on specific rights-of-way. It is most often touted as a means of traffic congestion relief, as it would drastically reduce following distances and headway, thus allowing more cars to occupy a given stretch of road.
In one scheme, the roadway has magnetized stainless-steel spikes driven one meter apart in its center. The car senses the spikes to measure its speed and locate the center of the lane. Furthermore, the spikes can have either magnetic north or magnetic south facing up. The roadway thus has small amounts of digital data describing interchanges, recommended speeds, etc.
The cars have power steering and automatic speed controls, which are controlled by a computer.
The cars organize themselves into platoons of eight to twenty-five cars. The platoons drive themselves a meter apart, so that air resistance is minimized. The distance between platoons is the conventional braking distance. If anything goes wrong, the maximum number of harmed cars should be one platoon.
The origin of research on AHS was done by a team from The Ohio State
Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time tactical digital communications of information of immediate value in the local area. In addition, all such data is ingested into the APRS Internet system (APRS-IS) and distributed globally for ubiquitous and immediate access. Along with messages, alerts, announcements and bulletins, the most visible aspect of APRS is its map display. Anyone may place any object or information on his or her map, and it is distributed to all maps of all users in the local RF network or monitoring the area via the Internet. Any station, radio or object that has an attached GPS is automatically tracked. Other prominent map features are weather stations, alerts and objects and other map-related amateur radio volunteer activities including Search and Rescue and signal direction finding.
APRS has been developed since the late 1980s by Bob Bruninga, callsign WB4APR, currently a senior research engineer at the United States Naval Academy. He still maintains the main APRS website. The acronym "APRS" was derived from his callsign.
Bob Bruninga implemented the earliest ancestor of APRS on an Apple II computer in 1982. This
ENG is a broadcasting (usually television) industry acronym which stands for electronic news gathering. It can mean anything from a lone broadcast journalist reporter taking a single professional video camera out to shoot a story, to an entire television crew taking a production truck or satellite truck on location to do a live television news report for a remote broadcast newscast.
The term ENG was created as television news departments moved from film based news gathering to electronic field production (EFP) generated images on video tape. All film requires a trip through a chemical bath (processing) before it can be viewed and edited. This generally added at least an hour from the time the film arrived back at the television station until it was ready to be seen by the viewing public (as in the cliché "Film at 11!"). Film was also difficult to handle, subject to easy scratching and other damage. Film editing was done by hand on what was known as "color reversal" film, meaning there was no negative film. Edits could not be changed without cutting segments out of the film itself. It was not that rare for the splices used for film edits to break on the air when the film was being
The LoJack Stolen Vehicle Recovery System is an aftermarket vehicle tracking system that allows vehicles to be tracked by police, with the aim of recovering them in case of theft. The manufacturer claims a 90% recovery rate. The name "LoJack" was coined to be the "antithesis of hijack", wherein "hijack" refers to the theft of a vehicle through force.
LoJack’s core business comprises the tracking and recovery of cars, trucks, construction equipment, commercial vehicles and motorcycles. However, LoJack is expanding into new markets through licensing agreements and investments in areas such as cargo security and people at risk of wandering (probationers, parolees, and Alzheimer's patients). LoJack Corporation claims that over 300,000 vehicles have been recovered worldwide since the product was introduced more than two decades ago.
The core of the LoJack Stolen Vehicle Recovery System is a small, silent radio transceiver that is clandestinely installed in a vehicle. The vehicle is not marked as possessing a LoJack transceiver, and the location of the transceiver within the vehicle varies from one car to the next. Once installed, the unit and the vehicle's VIN are registered in a
In telecommunications and radio communication, spread-spectrum techniques are methods by which a signal (e.g. an electrical, electromagnetic, or acoustic signal) generated with a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference, noise and jamming, to prevent detection, and to limit power flux density (e.g. in satellite downlinks).
This is a technique in which a (telecommunication) signal is transmitted on a bandwidth considerably larger than the frequency content of the original information.
Spread-spectrum telecommunications is a signal structuring technique that employs direct sequence, frequency hopping, or a hybrid of these, which can be used for multiple access and/or multiple functions. This technique decreases the potential interference to other receivers while achieving privacy. Spread spectrum generally makes use of a sequential noise-like signal structure to spread the normally narrowband information signal over a relatively wideband (radio) band of
The Very Long Baseline Array (VLBA) is a system of ten radio telescopes which are operated remotely from their Array Operations Center located in Socorro, New Mexico, as a part of the National Radio Astronomy Observatory (NRAO). These ten radio antennas work together as an array that forms the longest system in the world that uses very long baseline interferometry. The longest baseline available in this interferometer is about 8,611 kilometres (5,351 mi).
The construction of the VLBA began in February 1986 and it was completed in May 1993. The first astronometrical observation using all ten antenna was carried out on May 29, 1993. The total cost of building the VLBA was about 85 million dollars.
Each receiver in the VLBA consists of a parabolic dish antenna 25 meters (82 feet) in diameter, along with its adjacent control building. This contains the supporting electronics and machinery for the receiver, including low-noise electronics, digital computers, data storage units, and the antenna-pointing machinery. Each of the antennas is about as tall as a ten-story building when the antenna is pointed straight up, and each antenna weighs about 218 metric tons (240 short tons).
In telecommunications, identification, friend or foe (IFF) is an identification system designed for command and control. It enables military and national (civilian-located ATC) interrogation systems to identify aircraft, vehicles or forces as friendly and to determine their bearing and range from the interrogator.
IFF was first developed during World War II. The term is something of a misnomer, as IFF can only positively identify friendly targets but not hostile ones. If an IFF interrogation receives no reply or an invalid reply, the object cannot be identified as friendly but is not positively identified as a foe.
There are many reasons for friendly aircraft not to reply to IFF, such as battle damage or equipment failure, loss of encryption keys, and wrong encryption keys. Terrain-hugging aircraft are very often poor candidates for microwave line-of-sight systems such as the IFF system. Microwaves cannot penetrate terrain, and very often atmospheric effects (referred to as anomalous propagation) cause timing, range, and azimuth issues.
The world's first IFF, FuG 25a "Erstling" (English: "Debut"), was developed in Germany in 1940. It received the radar frequencies on 125 MHz (Freya
Astrotech Corporation (NASDAQ: ASTC), formerly Spacehab Inc., is an aerospace company headquartered in Austin, Texas which provides commercial space products and services to NASA, the U.S. Department of Defense, international space agencies, and global commercial customers. The Company changed its name to Astrotech Corporation in 2009 to align the corporate name with the company's core business offering, Astrotech Space Operation. Astrotech Space Operations provides all support necessary for government and commercial customers to successfully process their satellite hardware for launch, including planning; construction and use of unique equipment and facilities; and spacecraft checkout, encapsulation, fueling, and transport. In its 29 year history, Astrotech has supported the processing of more than 290 spacecraft without impacting a customer’s launch schedule.
The company was founded by Bob Citron with the help and support of CSP Associates from Cambridge, MA. The team from CSP Associates included founder David W. Lippy along with his partners Brad Meslin and Marc Oderman. It was one of CSP's consultants, Dr. David Williamson who conceived of the idea to increase the cargo space
The Army Ballistic Missile Agency (ABMA) was the agency formed to develop the US Army's first intermediate range ballistic missile. It was established at Redstone Arsenal on February 1, 1956 and commanded by Major General John B. Medaris with Doctor Wernher von Braun.
In the March, 1958 ABMA was placed under the new Army Ordnance Missile Command (AOMC) along with Redstone Arsenal, the Jet Propulsion Laboratory, White Sands Proving Ground and the Army Rocket and Guided Missile Agency (ARGMA). General Medaris was placed in command of AOMC and BG John A. Barclay took command of ABMA.
The Redstone missile was the first major project assigned to ABMA. After the US Naval Research Laboratory's Project Vanguard was chosen by the DOD Committee on Special Capabilities, over the ABMA's proposal to use a modified Redstone ballistic missile as a satellite launch vehicle, ABMA was ordered to stop work on satellites and focus, instead, on intermediate missiles.
Von Braun, disobeying orders, continued work on the design for what became the Jupiter-C IRBM. This was a three-stage rocket, which, by coincidence, could be used to launch a satellite in the Juno I configuration. In September 1956, the
The Digital Electronic Message Service (DEMS) is a two-way wireless radio service for passing of message and facsimile data using the 10.6 and 24 GHz band. As of 1997, Associated Communications was expected to use the band to create a network in 31 U.S. cities. In October 2005, the FCC moved part of the DEMS service from the 18/19 GHz band to 24 GHz.
Ground speed radar is a non-mechanical way of measuring the speed of a vehicle. The Speed sensor fires a radar beam towards the ground and measures the angle of the returning beam. This information is then sent to the engine control unit which calculates the forward speed.
The Naval Ocean Surveillance System (NOSS), reportedly also called White Cloud and PARCAE, refers to one or several systems of SIGINT satellites which conducted ELINT for the U.S. Navy beginning in the early 1970s.
The system is operated by the United States Navy and its main purpose was tactical geolocation of Soviet fleet assets during the Cold War. The NOSS satellites operate in clusters in low Earth orbit to detect radio transmissions from ships at sea and locate them using the "Time Difference Of Arrival" technique.
The costs of the NOSS satellites (excluding costs for the launch vehicle), which were destroyed in a Titan IV launch failure in 1993, were US$ 800 million (inflation adjusted US$ 1.3 billion in 2012).
Digital Audio Radio Service (DARS) refers to any type of digital radio service. In the United States it is the official FCC term for digital radio services.
The most popular type of DARS in the U.S. and Canada is SDARS: Satellite Digital Audio Radio Service, operated by XM Radio and Sirius. XM and Sirius both operate in the 2.3-GHz S band, from 2320 to 2345 MHz.
In areas with weak signals, such as downtown areas with tall buildings or parking garages which block satellite signals, Terrestrial repeaters are installed to re-broadcast the signal to ensure continuous coverage.
Increasing the spectrum available for more services would be difficult, since unlike C-band and Ku band services, which allow over 200 locations for satellites, S-band satellites must be spaced too far apart for current technology. Existing vehicle antennas would not allow reception of two different stations on the same frequency, though new technology, requiring different receivers, might be possible.
WorldSpace also operates a DARS network outside of the United States and Canada with a footprint covering Europe, Asia, the Middle East and Africa using the L-band.
HiperLAN (High Performance Radio LAN) is a Wireless LAN standard. It is a European alternative for the IEEE 802.11 standards (the IEEE is an international organization). It is defined by the European Telecommunications Standards Institute (ETSI). In ETSI the standards are defined by the BRAN project (Broadband Radio Access Networks). The HiperLAN standard family has four different versions.
Planning for the first version of the standard, called HiperLAN/1, started 1991, when planning of 802.11 was already going on. The goal of the HiperLAN was the high data rate, higher than 802.11. The standard was approved in 1996. The functional specification is EN300652, the rest is in ETS300836.
The standard covers the Physical layer and the Media Access Control part of the Data link layer like 802.11. There is a new sublayer called Channel Access and Control sublayer (CAC). This sublayer deals with the access requests to the channels. The accomplishing of the request is dependent on the usage of the channel and the priority of the request.
CAC layer provides hierarchical independence with Elimination-Yield Non-Preemptive Multiple Access mechanism (EY-NPMA). EY-NPMA codes priority choices and
Light Airborne Multi-Purpose System (LAMPS) is the United States Navy's program that developed manned helicopters that assist the surface fleet in anti-submarine warfare.
A Mk II version was planned, but was canceled in favor of the more advanced Mk III.
StarBand is a two-way satellite broadband Internet service available in the U.S.. StarBand Communications Inc. was initially a joint venture between Gilat Satellite Networks, EchoStar and Microsoft, and the StarBand service was launched in 2000. StarBand Communications filed for Chapter 11 bankruptcy in 2002 and emerged from bankruptcy in 2003. In March 2005, StarBand Communications was acquired by Spacenet, a division of Gilat Satellite Networks, which continues to operate the service. As of mid-2005, StarBand had approximately 32,000 subscribers.
The StarBand satellite Internet system is a VSAT platform that uses Ku band satellites for transmission of data from users' PCs to the StarBand network operations center. Two-way bandwidth for residential users is up to 1.5 Mbit/s download speed and 256 kbit/s upload speed, with unlimited usage and online hours. A 0.75 meter satellite dish is needed; the antenna is sufficiently small that Home Owner Associations cannot prohibit its installation.
StarBand offered the first residential two-way satellite Internet service in the United States market. Launched in November 2000, StarBand began selling the Gilat Satellite Networks SkyBlaster
The Karl G. Jansky Very Large Array (VLA) is a radio astronomy observatory located on the Plains of San Agustin, between the towns of Magdalena and Datil, some fifty miles (80 km) west of Socorro, New Mexico, USA. The VLA has made key observations of black holes and protoplanetary disks around young stars, discovered magnetic filaments and traced complex gas motions at the Milky Way's center, probed the Universe's cosmological parameters, and provided new knowledge about the physical mechanisms that produce radio emission.
The VLA stands at an elevation of 6970 ft (2124 m) above sea level. It is a component of the National Radio Astronomy Observatory (NRAO).
U.S. Route 60 passes through the complex, which is adjacent to the Boy Scout Double H High Adventure Base.
The observatory consists of 27 independent antennas, each of which has a dish diameter of 25 meters (82 feet) and weighs 209 metric tons (230 Short tons). The antennas are arrayed along the three arms of a Y-shape (each of which measures 21 km/13 miles long). Using the rail tracks that follow each of these arms—and that, at one point, intersect with U.S. Route 60 at a level crossing—and a specially designed lifting
Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. It allows observations of an object that are made simultaneously by many telescopes to be combined, emulating a telescope with a size equal to the maximum separation between the telescopes.
Data received at each antenna in the array is paired with timing information, usually from a local atomic clock, and then stored for later analysis on magnetic tape or hard disk. At that later time, the data is correlated with data from other antennas similarly recorded, to produce the resulting image. The resolution achievable using interferometry is proportional to the observing frequency and the distance between the antennas farthest apart in the array. The VLBI technique enables this distance to be much greater than that possible with conventional interferometry, which requires antennas to be physically connected by coaxial cable, waveguide, optical fiber, or other type of transmission line. The greater telescope separations are possible in VLBI due to the development of the closure phase imaging technique by Roger Jennison in the 1950s, allowing VLBI to produce images with superior
3G, short for 3rd Generation, is a term used to represent the 3rd generation of mobile telecommunications technology. This is a set of standards used for mobile devices and mobile telecommunication services and networks that comply with the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union. 3G finds application in wireless voice telephony, mobile Internet access, fixed wireless Internet access, video calls and mobile TV.
Several telecommunications companies market wireless mobile Internet services as 3G, indicating that the advertised service is provided over a 3G wireless network. Services advertised as 3G are required to meet IMT-2000 technical standards, including standards for reliability and speed (data transfer rates). To meet the IMT-2000 standards, a system is required to provide peak data rates of at least 200 kbit/s (about 0.2 Mbit/s). However, many services advertised as 3G provide higher speed than the minimum technical requirements for a 3G service. Recent 3G releases, often denoted 3.5G and 3.75G, also provide mobile broadband access of several Mbit/s to smartphones and mobile modems in laptop
The Air Route Surveillance Radar is used by the United States Air Force and the Federal Aviation Administration to control airspace within and around the borders of the United States.
The ARSR-4 is the FAA's most recent (late 80s, early 90s) addition to the "Long Range" series of radars, which are search radars with a range of at least 200 nautical miles (370 km). The Westinghouse system is solid state and has a 250-nautical-mile (460 km) range. In addition, the ARSR-4 features a "look down" capability that enables the radar to detect aircraft attempting to elude detection by flying at low altitudes, advanced clutter reduction via hardware and software post-processing, and enhanced poor-weather detection of aircraft. A Beacon system, the ATCBI-6M (a monopulse system), is installed along with each ARSR-4. However, since the ARSR-4 is a 3D radar, it is capable of determining aircraft altitude independently of its associated Beacon (albeit less accurately).
ARSR-4 systems are installed along the borders and coastal areas of the CONUS, Guantanamo Bay Naval Base in Cuba, the municipality of Yigo on Guam, and a training site at the FAA's Mike Monroney Aeronautical Center in Oklahoma
AMSAT is a name for amateur radio satellite organizations worldwide, but in particular the Radio Amateur Satellite Corporation (AMSAT-NA) with headquarters at Silver Spring, Maryland, near Washington DC. AMSAT organizations design, build, arrange launches for, and then operate (command) satellites carrying amateur radio payloads, including the OSCAR series of satellites. Other informally affiliated national organizations exist, such as AMSAT Germany (AMSAT-DL) and AMSAT Japan (JAMSAT).
AMSAT-NA was founded in 1969 in Washington DC to continue the efforts begun by Project OSCAR. Its first project was to coordinate the launch of OSCAR 5, constructed by students at the University of Melbourne. Some design modifications were needed and were made by AMSAT members, and the satellite was successfully launched on January 30, 1970 on a NASA Thor Delta launch vehicle.
AMSAT's next launch was AMSAT-OSCAR 6 (AO-6) on October 15, 1972. AO-6 was AMSAT's first long-life satellite, and was built with participants from Australia and West Germany. Command stations in Australia, Canada, Great Britain, Hungary, Morocco, New Zealand, the United States and West Germany controlled the satellite,
The Basic Exchange Telephone Radio Service or BETRS is a fixed radio service where a multiplexed, digital radio link is used as the last segment of the local loop to provide wireless telephone service to subscribers in remote areas. BETRS technology was developed in the mid-1980s and allows up to four subscribers to use a single radio channel pair, simultaneously, without interfering with one another.
In the U.S., this service may operate in the paired 152/158 and 454/459 MHz bands and on 10 channel blocks in the 816-820/861-865 MHz bands. BETRS may be licensed only to state-certified carriers in the area where the service is provided and is considered a part of the public switched telephone network (PSTN) by state regulators.
Regulation of this service currently resides in parts 1 and 22 of the Code of Federal Regulations (CFR), Subtitle 47 on Telecommunications, and may be researched or ordered through the Government Printing Office (GPO).
Source: Federal Communications Commission (Wireless Bureau)
GLONASS (Russian: ГЛОНАСС; IPA: [ɡlɐˈnas] - Глобальная Навигационная Спутниковая Система), acronym for Globalnaya Navigatsionnaya Sputnikovaya Sistema or Global Navigation Satellite System, is a radio-based satellite navigation system operated for the Russian government by the Russian Aerospace Defence Forces. It both complements and provides an alternative to the United States' Global Positioning System (GPS) and is the only alternative navigational system in operation with global coverage and of comparable precision.
Development of GLONASS began in the Soviet Union in 1976. Beginning on 12 October 1982, numerous rocket launches added satellites to the system until the "constellation" was completed in 1995. In the 2000s (decade), under Vladimir Putin's presidency, the restoration of the system was made a top government priority and funding was substantially increased. GLONASS is the most expensive program of the Russian Federal Space Agency, consuming a third of its budget in 2010.
By 2010, GLONASS had achieved 100% coverage of Russia's territory and in October 2011, the full orbital constellation of 24 satellites was restored, enabling full global coverage. The GLONASS
The High Performance Wireless Research and Education Network (HPWREN) is a network research program, funded by the National Science Foundation. The program includes the creation, demonstration, and evaluation of a non-commercial, prototype, high-performance, wide-area, wireless network in its Southern California service area.
The HPWREN program is a collaborative, interdisciplinary and multi-institutional cyber-infrastructure for research and education purposes. The program also provides data, and data transmission capabilities, to emergency first responders in its service area.
The program includes the creation, demonstration, and evaluation of a non-commercial, prototype, high-performance, wide-area, wireless network in its service area. Currently, the HPWREN network is used for network analysis research, and it also provides high-speed Internet access to field researchers.
Southern California, specifically San Diego, Riverside, and Imperial counties.
The network includes backbone nodes located at the University of California, San Diego (UCSD) and San Diego State University (SDSU) campuses, as well as a number of “hard-to-reach” areas in remote environments.
The HPWREN backbone
Hydropower or water power is power derived from the energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as watermills, sawmills, textile mills, dock cranes, domestic lifts and paint making.
Since the early 20th century, the term is used almost exclusively in conjunction with the modern development of hydro-electric power, which allowed use of distant energy sources. Another method used to transmit energy used a trompe, which produces compressed air from falling water. Compressed air could then be piped to power other machinery at a distance from the waterfall.
Water's power is manifested in hydrology, by the forces of water on the riverbed and banks of a river. When a river is in flood, it is at its most powerful, and moves the greatest amount of sediment. This higher force results in the removal of sediment and other material from the riverbed and banks of the river, locally causing erosion, transport and, with lower flow, sedimentation downstream.
Early uses of waterpower date back to Mesopotamia and ancient Egypt, where irrigation has been used
Milstar, originally meaning Military Strategic and Tactical Relay, is a constellation of communications satellites in geostationary orbit, which are operated by the United States Air Force, and provide secure and jam resistant worldwide communications to meet the requirements of the Armed Forces of the United States. Six spacecraft were launched between 1994 and 2003, of which five are operational, and the sixth was lost in a launch failure.
The first Milstar satellite was launched on 7 February 1994 aboard the first Titan IV(401)A rocket. It was followed by a second spacecraft on 7 November 1995. The first two satellites were Block I spacecraft, also known as Milstar Development Flight Satellites, or Milstar-DFS. The four later satellites were Block II spacecraft, which featured an additional medium data-rate payload. The first Block II satellite was launched on 30 April 1999, using a Titan IV(401)B rocket. Due to a programming error affecting the Centaur upper stage of its carrier rocket, it was placed into a lower orbit than had been planned, and it could not be raised into its operational orbit. It was the third consecutive, and last, failure of a Titan IV rocket. The remaining
MVDDS (Multichannel Video and Data Distribution Service) is a type of television and Internet delivery technology licensed for use in the United States by the Federal Communications Commission (FCC). This was subsequently tested by The MITRE Corporation for the FCC. A report was filed in the 98-206 Docket before the FCC.
This terrestrial based wireless transmission method reuses Direct Broadcast Satellite (DBS) frequencies for distribution of multichannel video and data over large distances.
The spectrum is in the 12.2 - 12.7 GHz range, offering fast downloads but requiring other frequencies for uploads. It is seen as a potential competitor to cable for delivery of triple play or triple-threat services (voice, data, video).
The MVDDS service was created as a result of a "Spectrum Grab" by the now defunct Northpoint Technology L.L.C. While Northpoint was fighting with the DBS companies, MDS America Inc provided the FCC with engineering information to assist the FCC in formulating the first US MVDDS rules. MDS America was granted permission to conduct experimental testing of their service in Clewiston Florida. This testing was completed by LCC International under the direction of
An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without a human pilot on board. Its flight is either controlled autonomously by computers in the vehicle, or under the remote control of a navigator, or pilot (in military UAVs called a Combat Systems Officer on UCAVs) on the ground or in another vehicle.
There are a wide variety of drone shapes, sizes, configurations, and characteristics. Historically, UAVs were simple remotely piloted aircraft, but autonomous control is increasingly being employed.
They are predominantly deployed for military applications, but also used in a small but growing number of civil applications, such as firefighting and nonmilitary security work, such as surveillance of pipelines. UAVs are often preferred for missions that are too 'dull, dirty, or dangerous' for manned aircraft.
The earliest attempt at a powered unmanned aerial vehicle was A. M. Low's "Aerial Target" of 1916. Nikola Tesla described a fleet of unmanned aerial combat vehicles in 1915. A number of remote-controlled airplane advances followed, including the Hewitt-Sperry Automatic Airplane, during and after World War I, including the first scale RPV (Remote Piloted
Airport Surface Detection Equipment, Model X, or ASDE-X, is a runway-safety tool that enables air traffic controllers to detect potential runway conflicts by providing detailed coverage of movement on runways and taxiways. By collecting data from a variety of sources, ASDE-X is able to track vehicles and aircraft on airport surfaces and obtain identification information from aircraft transponders.
Originally the FAA installed 38 ASDE-3A radar systems at the nation's busiest airports. The cost-effective alternative to the ASDE-3/AMASS capability, referred to as ASDE-X, is one of the first new runway safety program technologies aimed at improving ATCS situational awareness by providing tools to supplement their tasks (McAnulty, Doros, & Poston, 2001). The data that ASDE-X uses comes from a surface movement radar located on the airport traffic control tower or remote tower, multilateration sensors, ADS-B (Automatic Dependent Surveillance-Broadcast) sensors, terminal radars, the terminal automation system, and from aircraft transponders. By fusing the data from these sources, ASDE-X is able to determine the position and identification of aircraft and vehicles on the airport surfaces,
The AN/FPS-108 COBRA DANE radar is an active electronically scanned array installation operated by the United States Air Force at Eareckson Air Station on the island of Shemya, Alaska. This radar system was built in 1976 and brought on-line in 1977 for the primary mission of intelligence gathering in support of verification of the SALT II arms limitation treaty. Its single face radar with a 29 m (95 ft) diameter phased array radar antenna 52°44′14″N 174°05′29″E / 52.7373°N 174.0914°E / 52.7373; 174.0914 faces the Kamchatka Peninsula and Kura Test Range. Cobra Dane operates in the 1215-1400 MHz band.
It initially employed a Control Data Corporation Cyber 74 mainframe computer for data processing. Data from the radar is sent to the North American Aerospace Defense Command (NORAD) at Peterson Air Force Base, Colorado. It is also listed as a partner of the NASA Orbital Debris Program Office and works with the Missile Defense Agency.
The Ku band (/ˌkeɪˈjuː/) is a portion of the electromagnetic spectrum in the microwave range of frequencies. This symbol refers to (originally German: Kurz-unten)—in other words, the band directly below the K-band. In radar applications, it ranges from 12-18 GHz according to the formal definition of radar frequency band nomenclature in IEEE Standard 521-2002.
Ku band is primarily used for satellite communications, most notably for fixed and broadcast services, and for specific applications such as NASA's Tracking Data Relay Satellite used for both space shuttle and ISS communications. Ku band satellites are also used for backhauls and particularly for satellite from remote locations back to a television network's studio for editing and broadcasting. The band is split into multiple segments that vary by geographical region by the International Telecommunication Union (ITU). NBC was the first television network to uplink a majority of its affiliate feeds via Ku band in 1983.
Some frequencies in this radio band are used for vehicle speed detection by law enforcement, especially in Europe.
Segments in most of The Americas are represented by ITU Region 2 from 11.7 to 12.2 GHz (Local
The Local Area Augmentation System (LAAS) is an all-weather aircraft landing system based on real-time differential correction of the GPS signal. Local reference receivers located around the airport send data to a central location at the airport. This data is used to formulate a correction message, which is then transmitted to users via a VHF Data Link. A receiver on an aircraft uses this information to correct GPS signals, which then provides a standard ILS-style display to use while flying a precision approach. The International Civil Aviation Organization (ICAO) calls this type of system a Ground Based Augmentation System (GBAS).
The Local Area Augmentation System (LAAS) is designed to correct some of the errors inherent to GPS. One problem is the lack of a real-time, rapid-response monitoring system. Category I equipment will normally alert the user of the problem within ten seconds of detecting a problem. GPS has no such rapid-warning system. For example, if a satellite develops a clock problem, there is no way to rapidly warn the user not to use that satellite. WAAS, LAAS and other differential solutions fix this problem and provide GPS system integrity. Another problem is
Signals intelligence (often contracted to SIGINT) is intelligence-gathering by interception of signals, whether between people ("communications intelligence"—COMINT), whether involving electronic signals not directly used in communication ("electronic intelligence"—ELINT), or combinations of the two. As sensitive information is often encrypted, signals intelligence often involves the use of cryptanalysis. Also, traffic analysis—the study of who is signaling whom and in what quantity—can often produce valuable information, even when the messages themselves cannot be decrypted.
As a means of collecting intelligence, signals intelligence is a subset of intelligence collection management, which, in turn, is a subset of intelligence cycle management.
Intercepting written but encrypted communications, and extracting information, probably did not wait long after the development of writing. A simple encryption system, for example, is the Caesar cipher. Electronic interception appeared as early as 1900, during the Boer Wars. The Boers had captured some British radios, and, since the British were the only people transmitting at the time, no special interpretation of the signals was
An aerostat (From Greek ἀήρ aer (air) + στατός statos (standing) through French) is a craft that remains aloft primarily through the use of buoyant lighter than air gases, which impart lift to a vehicle with nearly the same overall density as air. Aerostats include free balloons, airships, and moored balloons. An aerostat's main structural component is its envelope, a lightweight skin containing a lifting gas to provide buoyancy, to which other components are attached. One of the most recent deployments of an aerostat was seen at the opening ceremony of the nineteenth 2010 Commonwealth Games, held in Delhi, India. The aerostat used in the ceremony was the largest in the world.
Aerostats are so named because they use "aerostatic" lift which is a buoyant force that does not require movement through the surrounding air mass. This contrasts with aerodynes that primarily use aerodynamic lift which requires the movement of at least some part of the aircraft through the surrounding air mass.
There are two distinct senses for the scope of term aerostat. In the broader sense, the term refers to all systems that remain aloft primarily using aerostatic buoyancy. In the narrower sense, the
Digital television (DTV) is the transmission of audio and video by digitally processed and multiplexed signal, in contrast to the totally analog and channel separated signals used by analog TV. It is an innovative service that represents a significant evolution in television technology since color television in the 1950s. Many countries are replacing broadcast analog television with digital television to allow other uses of the television radio spectrum. Several regions of the world are in different stages of adaptation and are implementing different broadcasting standards. There are four different digital television terrestrial broadcasting standards (DTTB) and they are: Advanced Television System Committee (ATSC) uses eight-level vestigial sideband (8 VSB) for terrestrial broadcasting. This standard has been adopted in the United States and in other countries. Digital Video Broadcasting-Terrestrial (DVB-T) uses coded orthogonal frequency-division multiplexing (C-OFDM) modulation and supports hierarchical transmission. This standard has been adapted in Europe and Australia. Terrestrial Integrated Services Digital Broadcasting (ISDB-T) is a system designed to provide good reception
DigitalGlobe (NYSE: DGI), of Longmont, Colorado, USA, is a commercial vendor of space imagery and geospatial content, and operator of civilian remote sensing spacecraft. The company went public on the New York Stock Exchange on 14 May 2009, selling 14.7 million shares at $19.00 each to raise $279 million in capital.
Worldview Imaging Corporation was founded in January 1992 in Oakland, California in anticipation of the 1992 Land Remote Sensing Policy Act (enacted in October 1992) which permitted private companies to enter the satellite imaging business. Its founder was Dr Walter Scott, who was joined by co-founder and CEO Doug Gerull in late 1992, The company had received the first high resolution commercial remote sensing satellite license issued under the 1992 Act. The company was initially funded with private financing from Silicon Valley sources and interested corporations in N. America, Europe, and Japan. Dr. Scott was head of the Lawrence Livermore Laboratories "Brilliant Pebbles" and "Brilliant Eyes" projects which were part of the Strategic Defense Initiative. Doug Gerull was the executive in charge of the Mapping Sciences division at the Intergraph Corporation. The
Galileo was an unmanned NASA spacecraft which studied the planet Jupiter and its moons. Named after the Renaissance astronomer Galileo Galilei, it was launched on October 18, 1989, by the Space Shuttle Atlantis on the STS-34 mission. Galileo arrived at Jupiter on December 7, 1995, via gravitational assist flybys of Venus and Earth, becoming the first spacecraft to orbit Jupiter. Despite suffering from antenna problems, Galileo conducted the first asteroid flyby near 951 Gaspra and discovered the first asteroid moon, Dactyl, around the asteroid 243 Ida. It furthermore launched the first probe into Jupiter's atmosphere. The mission's total cost was estimated at approximately US$1.4 billion.
The spacecraft measured the atmospheric composition of Jupiter and directly observed ammonia clouds, which seem to be created by an outflow from the lower depths of Jupiter's atmosphere. Galileo also registered Io's volcanism and the plasma interactions between its and Jupiter's atmospheres. Other data gave support for the popular theory of a liquid ocean under the icy surface of Europa. There were furthermore indications of similar liquid-saltwater layers under the surfaces of Ganymede and
The Iridium satellite constellation is a large group of satellites providing voice and data coverage to satellite phones, pagers and integrated transceivers over Earth's entire surface. Iridium Communications Inc. owns and operates the constellation and sells equipment and access to its services.
The constellation consists of 66 active satellites in orbit, and additional spare satellites to serve in case of failure. Satellites are in low Earth orbit at a height of approximately 485 mi (781 km) and inclination of 86.4°. Orbital velocity of the satellites is approximately 17,000 mph (27,000 km/h). Satellites communicate with neighboring satellites via Ka band inter-satellite links. Each satellite can have four inter-satellite links: two to neighbors fore and aft in the same orbital plane, and two to satellites in neighboring planes to either side. The satellites orbit from pole to pole with an orbit of roughly 100 minutes. This design means that there is excellent satellite visibility and service coverage at the North and South poles, where there are few customers. The over-the-pole orbital design produces "seams" where satellites in counter-rotating planes next to one another are
A macrocell is a cell in a mobile phone network that provides radio coverage served by a high power cellular base station (tower). Generally, macrocells provide coverage larger than microcell. The antennae for macrocells are mounted on ground-based masts, rooftops and other existing structures, at a height that provides a clear view over the surrounding buildings and terrain. Macrocell base stations have power outputs of typically tens of watts.
The term macrocell is used to describe the widest range of cell sizes. Macrocells are found in rural areas or along highways. Over a smaller cell area, a microcell is used in a densely populated urban area. Picocells are for areas even smaller than microcells. An example of usage would be a large office, a mall, or train station. Currently the smallest area of coverage can be implemented with a femtocell: used in homes or small offices.
A microcell is a cell in a mobile phone network served by a low power cellular base station (tower), covering a limited area such as a mall, a hotel, or a transportation hub. A microcell is usually larger than a picocell, though the distinction is not always clear. A microcell uses power control to limit the radius of its coverage area.
Typically the range of a microcell is less than two kilometers wide, a picocell is 200 meters or less, and a femtocell is on the order of 10 meters, although AT&T calls its product, with a range of 40 feet (12 m), a "microcell".
A microcellular network is a radio network composed of microcells.
Like picocells, microcells are usually used to add network capacity in areas with very dense phone usage, such as train stations. Microcells are often deployed temporarily during sporting events and other occasions in which extra capacity is known to be needed at a specific location in advance.
Cell size flexibility is a feature of 2G (and later) networks and is a significant part of how such networks have been able to improve capacity. Power controls implemented on digital networks make it easier to prevent interference from nearby cells using the same
Weather forecasting is the application of science and technology to predict the state of the atmosphere for a given location. Human beings have attempted to predict the weather informally for millennia, and formally since the nineteenth century. Weather forecasts are made by collecting quantitative data about the current state of the atmosphere and using scientific understanding of atmospheric processes to project how the atmosphere will evolve.
Once an all-human endeavor based mainly upon changes in barometric pressure, current weather conditions, and sky condition, weather forecasting now relies on computer-based models that take many atmospheric factors into account. Human input is still required to pick the best possible forecast model to base the forecast upon, which involves pattern recognition skills, teleconnections, knowledge of model performance, and knowledge of model biases. The chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe the atmosphere, error involved in measuring the initial conditions, and an incomplete understanding of atmospheric processes mean that forecasts become less accurate as the difference