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Radar Calibration Satellite
Radar calibration satellites are orbital satellites used to calibrate ground-based space surveillance radars. There are two types: active and passive. Passive satellites Passive calibration satellites are objects of known shape and size. Examples include the Lincoln Calibration Sphere 1 developed by the MIT Lincoln Laboratory. These are generally solid or hollow spheres, since that shape will have the same cross-section regardless of viewing angle, though later passive satellites used wire grid designs. A ground radar calculates the satellite's position using knowledge of the satellite's radar cross section, and this is compared with the satellite's known position and velocity. Active satellites Active calibration satellites are equipped with transponders that emit a signal on command. The ground radar station submits a transmit command and takes a measurement of the satellite's location. The transponder's signal is received by a radar receiver and combined with the satellite's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellites
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope thermoelectric generators (RTGs). Most satellites also have a method of communication to ground stations, called transponders. Many satellites use a standardized bus to save cost and work, the most popular of which is small CubeSats. Similar satellites can work together as a group, forming constellations. Because of the high launch cost to space, satellites are designed to be as lightweight and robust as possible. Most communication satellites are radio relay stations in orbit and carry dozens of transponders, each with a bandwidth of tens of megahertz. Satellites are placed from the surface to orbit by launch vehicles, high enough to avoid orbital decay by the atmosphere. Satellites can then change or maintain the orbit by propulsion, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Surveillance
Space domain awareness is the study and monitoring of satellites orbiting the earth. It involves the detection, tracking, cataloging and identification of artificial objects, i.e. active/inactive satellites, spent rocket bodies, or fragmentation debris. Aims Space domain awareness accomplishes the following: * Predicting when and where a decaying space object will re-enter the Earth's atmosphere; * Preventing a returning space object, which to radar looks like a missile, from triggering a false alarm in missile-attack warning sensors; * Charting the present position of space objects and plot their anticipated orbital paths; * Detecting new man-made objects in space; * Producing a running catalogue of man-made space objects; * Determining which country owns a re-entering space object; * Informing countries whether or not objects may interfere with satellites and International Space Station orbits; * Providing data for future anti-satellite weapons systems. Systems Systems in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lincoln Calibration Sphere 1
The Lincoln Calibration Sphere 1, or LCS-1, is a large aluminium sphere in Earth orbit since 6 May 1965. It is still in use, having lasted for over 50 years. The sphere was launched along with the Lincoln Experimental Satellite-2 on a Titan IIIA. It is technically the oldest operational spacecraft , but it has no power supply or fuel; it is merely a passive metal sphere. LCS-1 has been used for radar calibration since its launch. It was built by Rohr. Corp. for the MIT Lincoln Laboratory. LCS-1 is a hollow sphere in diameter with a wall thickness of . The sphere was constructed from two hemispheres, made by spinning sheet metal over a mold. These hemispheres were fastened to an internal, circumferential hoop by 440 countersunk screws, then milled and polished. The initial finish had a surface roughness Surface roughness, often shortened to roughness, is a component of surface finish (surface texture). It is quantified by the deviations in the direction of the normal vector ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MIT Lincoln Laboratory
The MIT Lincoln Laboratory, located in Lexington, Massachusetts, is a United States Department of Defense federally funded research and development center chartered to apply advanced technology to problems of national security. Research and development activities focus on long-term technology development as well as rapid system prototyping and demonstration. Its core competencies are in sensors, integrated sensing, signal processing for information extraction, decision-making support, and communications. These efforts are aligned within ten mission areas. The laboratory also maintains several field sites around the world. The laboratory transfers much of its advanced technology to government agencies, industry, and academia, and has launched more than 100 start-ups. History Origins At the urging of the United States Air Force, the Lincoln Laboratory was created in 1951 at the Massachusetts Institute of Technology (MIT) as part of an effort to improve the U.S. air defense syste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radar Cross Section
Radar cross-section (RCS), also called radar signature, is a measure of how detectable an object is by radar. A larger RCS indicates that an object is more easily detected. An object reflects a limited amount of radar energy back to the source. The factors that influence this include: *the material with which the target is made; *the size of the target relative to the wavelength of the illuminating radar signal; *the absolute size of the target; *the incident angle (angle at which the radar beam hits a particular portion of the target, which depends upon the shape of the target and its orientation to the radar source); *the reflected angle (angle at which the reflected beam leaves the part of the target hit; it depends upon incident angle); *the polarization of the transmitted and the received radiation with respect to the orientation of the target. While important in detecting targets, strength of emitter and distance are not factors that affect the calculation of an RCS becaus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transponder
In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend word, blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a Transponder (aeronautics), flight transponder is an automated transceiver in an aircraft that emits a coded identifying signal in response to an interrogating received signal. In a communications satellite, a Transponder (satellite communications), satellite transponder receives signals over a range of uplink frequencies, usually from a satellite ground station; the transponder amplifies them, and re-transmits them on a different set of downlink frequencies to receivers on Earth, often without changing the content of the received signal or signals. Satellite/broadcast communications A communications satellite’s Communication channel, channels are called transponders because each is a separate transceiver or repeater. With digital video d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ephemeris
In astronomy and celestial navigation, an ephemeris (pl. ephemerides; ) is a book with tables that gives the trajectory of naturally occurring astronomical objects as well as artificial satellites in the sky, i.e., the position (and possibly velocity) over time. Historically, positions were given as printed tables of values, given at regular intervals of date and time. The calculation of these tables was one of the first applications of mechanical computers. Modern ephemerides are often provided in electronic form. However, printed ephemerides are still produced, as they are useful when computational devices are not available. The astronomical position calculated from an ephemeris is often given in the spherical polar coordinate system of right ascension and declination, together with the distance from the origin if applicable. Some of the astronomical phenomena of interest to astronomers are eclipses, apparent retrograde motion/planetary stations, planetary es, sidereal tim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naval Research Laboratory
The United States Naval Research Laboratory (NRL) is the corporate research laboratory for the United States Navy and the United States Marine Corps. It was founded in 1923 and conducts basic scientific research, applied research, technological development and prototyping. The laboratory's specialties include plasma physics, space physics, materials science, and tactical electronic warfare. NRL is one of the first US government scientific R&D laboratories, having opened in 1923 at the instigation of Thomas Edison, and is currently under the Office of Naval Research. As of 2016, NRL was a Navy Working Capital Fund activity, which means it is not a line-item in the US Federal Budget. Instead of direct funding from Congress, all costs, including overhead, were recovered through sponsor-funded research projects. NRL's research expenditures were approximately $1 billion per year. Research The Naval Research Laboratory conducts a wide variety of basic research and applied r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RADCAL
RADCAL (short for RADar CALibration Satellite) was a radar calibration satellite launched and operated by the United States Air Force. It was active from June 1993 until it stopped communicating in May 2013. Design Construction RADCAL was built by Defense Systems Inc. as United States Air Force Space Test Program payload P92-1. It was built under a one-year contract-to-launch and cost $10 million. Components Payload included two C Band transponders (operating at the same frequency as space-detection radars), a Doppler beacon that transmitted at 150 and 400 MHz, and a pair of modified Trimble Inc. TANS Quadrex Global Positioning System receivers. The receivers were used to determine the satellite's orbit as a reference for calibrating space detection radars. It also carried the Small Satellite Power System Regulator, an experiment testing improved battery charging on solar panel-equipped vehicles. Mission Launch RADCAL launched into polar orbit at 23:30:00 UTC on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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