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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] |
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] |
United States Air Force
The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal Corps, the USAF was established as a separate branch of the United States Armed Forces in 1947 with the enactment of the National Security Act of 1947. It is the second youngest branch of the United States Armed Forces and the fourth in order of precedence. The United States Air Force articulates its core missions as air supremacy, global integrated intelligence, surveillance and reconnaissance, rapid global mobility, global strike, and command and control. The United States Air Force is a military service branch organized within the Department of the Air Force, one of the three military departments of the Department of Defense. The Air Force through the Department of the Air Force is headed by the civilian Secretary of the Air Force ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polar Orbit
A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of about 60 - 90 degrees to the body's equator. Launching satellites into polar orbit requires a larger launch vehicle to launch a given payload to a given altitude than for a near-equatorial orbit at the same altitude, because it cannot take advantage of the Earth's rotational velocity. Depending on the location of the launch site and the inclination of the polar orbit, the launch vehicle may lose up to 460 m/s of Delta-v, approximately 5% of the Delta-v required to attain Low Earth orbit. Usage Polar orbits are used for Earth-mapping, reconnaissance satellites, as well as for some weather satellites.Science Focus 2nd Edition 2, pg. 297 The Iridium satellite constellation uses a polar orbit to provide telecommunications services. Near-polar orb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Radars
Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum known as spacetime. The concept of space is considered to be of fundamental importance to an understanding of the physical universe. However, disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework. Debates concerning the nature, essence and the mode of existence of space date back to antiquity; namely, to treatises like the ''Timaeus'' of Plato, or Socrates in his reflections on what the Greeks called ''khôra'' (i.e. "space"), or in the ''Physics'' of Aristotle (Book IV, Delta) in the definition of ''topos'' (i.e. place), or in the later "geometrical conception of place" as "space ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spacecraft Launched In 1993
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, planetary exploration, and transportation of humans and cargo. All spacecraft except single-stage-to-orbit vehicles cannot get into space on their own, and require a launch vehicle (carrier rocket). On a sub-orbital spaceflight, a space vehicle enters space and then returns to the surface without having gained sufficient energy or velocity to make a full Earth orbit. For orbital spaceflights, spacecraft enter closed orbits around the Earth or around other celestial bodies. Spacecraft used for human spaceflight carry people on board as crew or passengers from start or on orbit (space stations) only, whereas those used for robotic space missions operate either autonomously or telerobotically. Robotic spacecraft used to support scientific re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spacecraft Attitude Control
Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle/satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle attitude requires sensors to measure vehicle orientation, actuators to apply the torques needed to orient the vehicle to a desired attitude, and algorithms to command the actuators based on (1) sensor measurements of the current attitude and (2) specification of a desired attitude. The integrated field that studies the combination of sensors, actuators and algorithms is called guidance, navigation and control (GNC). Overview A spacecraft's attitude must typically be stabilized and controlled for a variety of reasons. It is often needed so that the spacecraft high-gain antenna may be accurately pointed to Earth for communications, so that onboard experiments may accomplish precise pointing for accurate collectio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Defense Meteorological Satellite Program
The Defense Meteorological Satellite Program (DMSP) monitors meteorological, oceanographic, and solar-terrestrial physics for the United States Department of Defense. The program is managed by the United States Space Force with on-orbit operations provided by the National Oceanic and Atmospheric Administration (NOAA). The (originally classified) mission of the satellites was revealed in March 1973. They provide cloud cover imagery from polar orbits that are Sun-synchronous at nominal altitude of . History During the 1960s, one of the most important projects that the United States civil space program was involved in dealt with meteorology and weather forecasting. Unbeknownst to many, the U.S. military services were also starting up a weather satellite program. This program, the DMSP, would relay important weather and climate data to the military for more effective operations. From the onset of the DMSP program, knowledge of its existence was limited to "need-to-know" person ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vandenberg Air Force Base
Vandenberg may refer to: * Vandenberg (surname), including a list of people with the name * USS General Harry Taylor (AP-145), USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in Key West, Florida * Vandenberg Space Force Base, a United States military installation with a spaceport * Vandenberg (band), a Dutch hard rock band ** Vandenberg (album), ''Vandenberg'' (album), their 1982 debut album * Vandenberg resolution, a United States Congress resolution passed in 1948 {{disambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trimble Inc
Trimble Inc. is an American software, hardware, and services technology company. Trimble supports global industries in building & construction, agriculture, geospatial, natural resources and utilities, governments, transportation and others. Trimble also does hardware development of global navigation satellite system (GNSS) receivers, scanners, laser rangefinders, unmanned aerial vehicles (UAVs), inertial navigation systems and software processing tools. History Trimble Navigation was founded in November 1978 by Charles Trimble and two partners from Hewlett Packard. It initially operated above a movie theatre in Los Altos, California. By the end of 2016, the company had 8,388 employees, with more than half of employees in locations outside the United States. The company's acquisitions include Telog Instruments, Pocket Mobile AB, @Road, Cengea Solutions Inc., Datacom Software Research, Spectra Precision Group, Tripod Data Systems, Advanced Public Safety, Inc., ALK Technologies, A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Positioning System
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It does not require the user to transmit any data, and operates independently of any telephonic or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls and maintains the GPS system, it is freely accessible to anyone with a GPS receiver. The GPS project was started by the U.S. Department of Defense in 1973. The first prototype spacecraft was lau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scout (rocket Family)
The Scout family of rockets were American launch vehicles designed to place small satellites into orbit around the Earth. The Scout multistage rocket was the first orbital launch vehicle to be entirely composed of solid fuel stages. It was also the only vehicle of that type until the successful launch of the Japanese Lambda 4S in 1970. The original Scout (an acronym for Solid Controlled Orbital Utility Test system) was designed in 1957 at the NACA, at Langley center. Scout launch vehicles were used from 1961 until 1994. To enhance reliability the development team opted to use "off the shelf" hardware, originally produced for military programs. According to the NASA fact sheet: "... the first stage motor was a combination of the Jupiter Senior and the Navy Polaris; the second stage came from the Army MGM-29 Sergeant; and the third and fourth stage motors were designed by Langley engineers who adapted a version of the Navy Vanguard." The first successful orbital launch of a Sco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C Band (IEEE)
The C band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 4.0 to 8.0 gigahertz (GHz). However, the U.S. Federal Communications Commission C band proceeding and auction, designated 3.7–4.2 GHz as C band. The C band is used for many satellite communications transmissions, some Wi-Fi devices, some cordless telephones, as well as some Radar and weather radar systems. Use in satellite communication The communications C band was the first frequency band that was allocated for commercial telecommunications via satellites. The same frequencies were already in use for terrestrial microwave radio relay chains. Nearly all C-band communication satellites use the band of frequencies from 3.7 to 4.2 GHz for their downlinks, and the band of frequencies from 5.925 to 6.425 GHz for their uplinks. Note that by using the band from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
