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Space-based radar refers to space-borne radar systems that may have any of a variety of purposes. Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships 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. Active radar homing is a Missile guidance method in which a Guided missile contains a Radar Transceiver and the electronics necessary for it This article is about artificial satellites For natural satellites also known as moons see Natural satellite. The United States of America —commonly referred to as the The United States Department of Defense ( DOD or DoD) is the federal department charged with coordinating and supervising all agencies and functions of the government 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. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 Radar Ocean Reconnaissance SATellite or RORSAT is the western name given to the Soviet Upravlyaemyj Sputnik Aktivnyj (Управляемый Спутник Активный This information would then be relayed to regional and national command centers, as well as E-10 MC2A airborne command posts. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout

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Earth-Observing Radars

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. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program SEASAT was the first Earth-orbiting Satellite designed for Remote sensing of the Earth 's Oceans and had onboard the first spaceborne Synthetic-aperture radar (SAR is a form of Radar in which the highly-directional (and thus very large rotating antenna used by conventional radar is replaced with many low-directivity A radar altimeter, radio altimeter, low range radio altimeter (LRRA or simply RA measures Altitude above the Terrain presently beneath A radar scatterometer is designed to determine the normalized Radar cross section (sigma-0 of the surface SEASAT was the first Earth-orbiting Satellite designed for Remote sensing of the Earth 's Oceans and had onboard the first spaceborne

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 very high range resolution, which allows to measure (with an accuracy in the order of few centimeters) the sea surface profile. Additionally, analysis of the echo amplitude and shape allows to extract information about the wind speed and wave height, respectively. Some radar-altimeters (like CryoSat/SIRAL) employ synthetic aperture and/or interferometric techniques: their reduced footprint allows mapping of rougher surfaces like polar ices. CryoSat was an ESA Satellite that was destroyed on launch October 8, 2005 when the second stage engine of a modified Russian SS-19 Synthetic-aperture radar (SAR is a form of Radar in which the highly-directional (and thus very large rotating antenna used by conventional radar is replaced with many low-directivity Interferometric synthetic aperture radar, also abbreviated InSAR or IfSAR, is a Radar technique used in Geodesy and Remote sensing

A wind scatterometer observes the same portion of the ocean surface from different (at least 3) angles of view as the satellite passes by, measuring the echo amplitude and the corresponding surface reflectivity. A radar scatterometer is designed to determine the normalized Radar cross section (sigma-0 of the surface Being it affected by the ocean surface "roughness", in turn affected by the wind and also dependent from its direction, it is possible to determine the wind speed and direction.

These three types of radar are currently used on several satellites. Scatterometers are of high value for operational meteorology, allowing reconstruction of wind fields on a global scale. A radar scatterometer is designed to determine the normalized Radar cross section (sigma-0 of the surface Data from Radar altimeters are used for the accurate determination of the geoid, monitoring of tides, ocean currents and other large-scale ocean phenomena such as el nino. A radar altimeter, radio altimeter, low range radio altimeter (LRRA or simply RA measures Altitude above the Terrain presently beneath

SARs applications are countless: they range from geology to crop monitoring, from sea-ice mapping to disaster monitoring to vessels traffic surveillance. . . not to forget the military applications (many civilian SAR satellites are, in fact, dual-use systems). SAR imaging offer the great advantage, over its optical counterparts, of not being affected by meteorological conditions such as clouds, fog, etc. , making it the sensor of choice when continuity of data must be ensured. Additionally, SAR interferometry (both dual-pass or single-pass, as used in the STRM mission) allows accurate 3-D Reconstruction. Interferometric synthetic aperture radar, also abbreviated InSAR or IfSAR, is a Radar technique used in Geodesy and Remote sensing The Shuttle Radar Topography Mission ( SRTM) is an international research effort that obtained Digital elevation models on a near-global scale from 56 °S to 60 °N

Other types of radars have been flown for earth observation missions: precipitation radars such as the Tropical Rainfall Measuring Mission, or cloud radars like the one used on Cloudsat. The Tropical Rainfall Measuring Mission ( TRMM) is a joint Space mission between NASA and the Japan Aerospace Exploration Agency (JAXA designed CloudSat is a NASA Earth observation satellite, which was launched on a Delta II rocket on 28 April 2006.

Like the majority of earth-observing satellites, also radar satellites often use sun-synchronous orbits so that diurnal variations of vegetation are ignored, allowing long-term variations to be more accurately measured. This article is about a class of orbits about the Earth For a class of orbits around the sun see Heliosynchronous orbit.

Some of the former and current earth-observing radar satellites are:

Planetary Radars

Most of the radars flown as payload in planetary missions (i. SEASAT was the first Earth-orbiting Satellite designed for Remote sensing of the Earth 's Oceans and had onboard the first spaceborne RADARSAT-1 is Canada 's first commercial Earth observation satellite. RADARSAT-2 is an Earth observation satellite that was successfully launched December 14 2007 for the SAR-Lupe is Germany 's first Reconnaissance satellite system SAR is an abbreviation for Synthetic Aperture Radar and "Lupe" is German for Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. ( German 'luftvafe is a generic German term for an Air force. Launched in 1992 TOPEX/Poseidon was a joint satellite mission between NASA, the U Jason-1 is a Satellite oceanography mission to monitor global Ocean circulation, study the ties between the Ocean and the Atmosphere, improve The Shuttle Radar Topography Mission ( SRTM) is an international research effort that obtained Digital elevation models on a near-global scale from 56 °S to 60 °N The Japanese Earth Resources Satellite 1 ( JERS-1) was a Satellite launched in 1992 by the Japan Aerospace Exploration Agency (at that time also The GEOSAT (GEOdetic SATellite was a US Navy Earth observation satellite, launched on March 12, 1985 into an 800 km 108-deg inclination orbit carrying European Remote sensing Satellite ( ERS) was the European Space Agency 's first Earth-observing satellite. Envisat (Environmental Satellite is an Earth-observing satellite built by the European Space Agency. The Tropical Rainfall Measuring Mission ( TRMM) is a joint Space mission between NASA and the Japan Aerospace Exploration Agency (JAXA designed CloudSat is a NASA Earth observation satellite, which was launched on a Delta II rocket on 28 April 2006. Background The Television Infrared Observation Satellite (TIROS series of polar-orbiting satellites was launched in 1960 See also Earth Observing System European Remote-Sensing Satellite e. , not considering avionics radar, such as docking and landing radars used in Apollo and LEM) belong to two categories: imaging radars and sounders.

Imaging radars: Imaging (i. e. , Synthetic aperture radars) are the only instruments capable to penetrate cloud covers such as that of Venus. Synthetic-aperture radar (SAR is a form of Radar in which the highly-directional (and thus very large rotating antenna used by conventional radar is replaced with many low-directivity The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University And Venus has, in fact, been the first target for such missions. The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University It has been imaged by two soviet spacecrafts, Venera 15 and Venera 16 in 1983/84 (carrying also a Radar altimeter), and by the American spacecraft Magellan in 1990/94. Venera 15 (Венера-15 was a Spacecraft sent to Venus by the Soviet Union. Venera 16 (Венера-16 was a Spacecraft sent to Venus by the Soviet Union. A radar altimeter, radio altimeter, low range radio altimeter (LRRA or simply RA measures Altitude above the Terrain presently beneath The Magellan spacecraft was a space probe sent to the planet Venus, the first post- Voyager unmanned spacecraft to be launched by NASA

The other Solar system's body targeted by an imaging radar mission has been Titan, the largest moon of Saturn, to penetrate its opaque atmosphere. The Solar System consists of the Sun and those celestial objects bound to it by Gravity. Traditional Radar sends directional pulses of Electromagnetic energy and detects the presence position and motion of an object (such as an Aircraft) by analyzing TemplateInfobox Planet.--> Titan (ˈtaɪtən, or as The Radar of the Cassini probe, in orbit around Saturn, is currently providing images of Titan surface at each fly-by of the moon. Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its TemplateInfobox Planet.--> Titan (ˈtaɪtən, or as The Cassini radar is a multimode system and can operate as Synthetic aperture radar, Radar altimeter, Scatterometer and Radiometer. Synthetic-aperture radar (SAR is a form of Radar in which the highly-directional (and thus very large rotating antenna used by conventional radar is replaced with many low-directivity A radar altimeter, radio altimeter, low range radio altimeter (LRRA or simply RA measures Altitude above the Terrain presently beneath A radar scatterometer is designed to determine the normalized Radar cross section (sigma-0 of the surface A radiometer is a device for measuring the radiant flux (power of Electromagnetic radiation.

Its antenna also serves as main antenna for communication with Earth. An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001

Sounding radars: these are low-frequency (normally, HF - 3 to 30 MHz - or lower) ground-penetrating Radars, used to acquire data about the planet sub-surface structure. Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships Thanks to their low operating frequency they can penetrate for hundred of meters, or even kilometers, below the surface. Synthetic aperture techniques are normally exploited to reduce the ground footprint (due to the low operating frequency and the small allowable antenna dimensions, the beam is very wide) and, thus, the unwanted echo from other surface objects. An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into

The first radar sounder flown has been ALSE (Apollo Lunar Sounder Experiment) on board Apollo 17 in 1972. The ALSE (Apollo Lunar Sounder Experiment (also known as Scientific Experiment S-209 according to NASA designations was a Ground-penetrating radar (subsurface sounder experiment

Other sounder instruments flown (in this case around Mars), are MARSIS (Mars Advanced Radar for SubSurface and Ionosphere Sounding) on board the European Space Agency's Mars Express probe, and SHARAD (mars SHAllow RADar sounder) on JPL's Mars Reconnaissance Orbiter (MRO). MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding is a low frequency pulse-limited Radar sounder and Altimeter used on the ESA The ionosphere is the uppermost part of the atmosphere, distinguished because it is Ionized by solar radiation The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member Mars Express is a Space exploration mission being conducted by the European Space Agency (ESA Sharad is the word for early Autumn in the Hindu calendar. It roughly corresponds to the Western months of October and November NASA 's Mars Reconnaissance Orbiter ( MRO) is a multipurpose Spacecraft designed to conduct Reconnaissance and exploration of Mars Both are currently operational.

A similar instrument (mainly devoted to ionospheric plasma probing) was embarked on the Japanese martian mission Nozomi (launched in 1998 but lost). In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound Nozomi (のぞみ ( Japanese for "Wish" and known before launch as Planet-B) was planned as a Mars - Orbiting Aeronomy A radar sounder is also used on the Japanese moon probe SELENE, launched September 14, 2007. In Greek mythology, Selene (Σελήνη " Moon " English sɛˈliːniː was an archaic Lunar deity and the daughter of the Titans

Defense Radars

Discoverer II was a proposed military space-based radar program initiated in February 1998 as a joint Air Force, DARPA, and NRO program. Lacrosse and Onyx are the code names for the United States' National Reconnaissance Office terrestrial Radar imaging Reconnaissance satellite SAR-Lupe is Germany 's first Reconnaissance satellite system SAR is an abbreviation for Synthetic Aperture Radar and "Lupe" is German for The Defense Advanced Research Projects Agency (DARPA is an agency of the United States Department of Defense responsible for the development of new Technology The National Reconnaissance Office ( NRO) located in Chantilly The concept was to provide high-range-resolution ground moving target indication (GMTI), as well as SAR imaging and high-resolution digital mapping. Moving target indication ( MTI) is a mode of operation of a Radar to discriminate a target against clutter. This program was cancelled by Congress in 2000. SBR is a less-ambitious version of Discoverer II.

External links

The Air Force Association ( AFA) is an independent nonprofit civilian organization promoting public understanding of aerospace power headquartered in Arlington Virginia See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar.
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