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79-669: The Transit satellite system, sponsored by the Navy and developed jointly by DARPA and the Johns Hopkins Applied Physics Laboratory , under the leadership of Dr. Richard Kershner at Johns Hopkins, was the first satellite-based geopositioning system. Just days after the Soviet launch of Sputnik 1 , the first man-made Earth-orbiting satellite on October 4, 1957, two physicists at APL, William Guier and George Weiffenbach, found themselves in discussion about

158-739: A SNAP-3 RTG . Transit 5B-2 (1963) had a SNAP-9A RTG. In 1964, a rocket failed to boost Transit 5BN-3 with a SNAP-9A RTG into orbit. It "burned up during re-entry and ablated into small particles" together with its approximately 1 kilogram of Plutonium-238. Transit 5B-5 resumed communicating again after an extended period of inactivity (a zombie satellite ). Transit-9 and 5B4 (1964) and Transit-5B7 and 5B6 (1965) each had "a nuclear power source". The US Air Force also periodically launched short lived satellites equipped with radio beacons of 162 MHz and 324 MHz at much lower orbits to study orbital drag . The Transit ground tracking stations tracked these satellites as well, locating

237-570: A domino effect known as Kessler syndrome . NASA's Orbital Debris Program tracks over 25,000 objects larger than 10 cm diameter in LEO, while the estimated number between 1 and 10 cm is 500,000, and the number of particles bigger than 1 mm exceeds 100 million. The particles travel at speeds up to 7.8 km/s (28,000 km/h; 17,500 mph), so even a small impact can severely damage a spacecraft. [REDACTED]  This article incorporates public domain material from websites or documents of

316-404: A semi-major axis of 8,413 km (5,228 mi). For circular orbits, this in turn corresponds to an altitude of 2,042 km (1,269 mi) above the mean radius of Earth, which is consistent with some of the upper altitude limits in some LEO definitions. The LEO region is defined by some sources as a region in space that LEO orbits occupy. Some highly elliptical orbits may pass through

395-457: A collision risk to the many LEO satellites. No human spaceflights other than the lunar missions of the Apollo program (1968-1972) and the 2024 Polaris Dawn have taken place beyond LEO. All space stations to date have operated geocentric within LEO. A wide variety of sources define LEO in terms of altitude . The altitude of an object in an elliptic orbit can vary significantly along

474-570: A cooperation among Bell Labs , General Electric and MIT , which DARPA supported by funding Project MAC at MIT with an initial two-million-dollar grant. DARPA supported the evolution of the ARPANET (the first wide-area packet switching network), Packet Radio Network, Packet Satellite Network and ultimately, the Internet and research in the artificial intelligence fields of speech recognition and signal processing, including parts of Shakey

553-412: A location, also known as "taking a fix", normally requires two or more measurements to be taken to produce a 2D location. In the case of the modern GPS system, dozens of such measurements may be taken depending on which satellites are visible at that time, each one helping improve accuracy. In the case of Transit, only a small number of satellites were in orbit and were spread out. This generally meant there

632-666: A number of new technologies that were developed within the framework of the GXV-T program. The goal of this program is to create a lightly armored combat vehicle of not very large dimensions, which, due to maneuverability and other tricks, can successfully resist modern anti-tank weapon systems. In September 2020, DARPA and the US Air Force announced that the Hypersonic Air-breathing Weapon Concept (HAWC) are ready for free-flight tests within

711-524: A receiver on Earth, and proposed a satellite system to implement this principle. Development of the Transit system began in 1958, and a prototype satellite, Transit 1A , was launched in September 1959. That satellite failed to reach orbit. A second satellite, Transit 1B , was successfully launched April 13, 1960, by a Thor-Ablestar rocket. The first successful tests of the system were made in 1960, and

790-543: A satellite into a LEO, and a satellite there needs less powerful amplifiers for successful transmission, LEO is used for many communication applications, such as the Iridium phone system . Some communication satellites use much higher geostationary orbits and move at the same angular velocity as the Earth as to appear stationary above one location on the planet. Unlike geosynchronous satellites , satellites in low orbit have

869-570: A slow-moving ship, even with reception of just one two-minute Doppler curve. This was the navigation criterion demanded by the U.S. Navy, since American submarines would normally expose their UHF antenna for only 2 minutes to obtain a usable Transit fix. The U.S. submarine version of the Transit system also included a special encrypted, more accurate version of the downloaded satellite's orbital data. This enhanced data allowed for considerably enhanced system accuracy [not unlike Selective Availability (SA) under GPS]. Using this enhanced mode, accuracy

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948-441: A small field of view and can only observe and communicate with a fraction of the Earth at a given time. This means that a large network (or constellation ) of satellites is required to provide continuous coverage. Satellites at lower altitudes of orbit are in the atmosphere and suffer from rapid orbital decay , requiring either periodic re-boosting to maintain stable orbits, or the launching of replacements for those that re-enter

1027-549: A stable low Earth orbit is about 7.8 km/s (4.8 mi/s), which translates to 28,000 km/h (17,000 mph). However, this depends on the exact altitude of the orbit. Calculated for a circular orbit of 200 km (120 mi) the orbital velocity is 7.79 km/s (4.84 mi/s), but for a higher 1,500 km (930 mi) orbit the velocity is reduced to 7.12 km/s (4.42 mi/s). The launch vehicle's delta-v needed to achieve low Earth orbit starts around 9.4 km/s (5.8 mi/s). The pull of gravity in LEO

1106-433: A subset of LEO. These orbits, with low orbital inclination , allow rapid revisit times over low-latitude locations on Earth. Prograde equatorial LEOs also have lower delta-v launch requirements because they take advantage of the Earth's rotation. Other useful LEO orbits including polar orbits and Sun-synchronous orbits have a higher inclinations to the equator and provide coverage for higher latitudes on Earth. Some of

1185-562: A whole series of X planes over the next 10 years. Between 2014 and 2016, DARPA shepherded the first machine-to-machine computer security competition, the Cyber Grand Challenge (CGC), bringing a group of top-notch computer security experts to search for security vulnerabilities , exploit them, and create fixes that patch those vulnerabilities in a fully automated fashion. It is one of DARPA prize competitions to spur innovations. In June 2018, DARPA leaders demonstrated

1264-469: Is Stefanie Tompkins . As of 2021 , their mission statement is "to make pivotal investments in breakthrough technologies for national security". The Advanced Research Projects Agency (ARPA) was suggested by the President's Scientific Advisory Committee to President Dwight D. Eisenhower in a meeting called after the launch of Sputnik. ARPA was formally authorized by President Eisenhower in 1958 for

1343-684: Is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Advanced Research Projects Agency ( ARPA ), the agency was created on February 7, 1958, by President Dwight D. Eisenhower in response to the Soviet launching of Sputnik 1 in 1957. By collaborating with academia, industry, and government partners, DARPA formulates and executes research and development projects to expand

1422-586: Is credited with boosting the development of the fledgling personal computer industry. Some young computer scientists left the universities to startups and private research laboratories such as Xerox PARC . Between 1976 and 1981, DARPA's major projects were dominated by air, land, sea, and space technology, tactical armor and anti-armor programs, infrared sensing for space-based surveillance, high-energy laser technology for space-based missile defense, antisubmarine warfare, advanced cruise missiles, advanced aircraft, and defense applications of advanced computing. Many of

1501-496: Is only slightly less than on the Earth's surface. This is because the distance to LEO from the Earth's surface is much less than the Earth's radius. However, an object in orbit is in a permanent free fall around Earth, because in orbit the gravitational force and the centrifugal force balance each other out. As a result, spacecraft in orbit continue to stay in orbit, and people inside or outside such craft continuously experience weightlessness . Objects in LEO orbit Earth between

1580-597: The National Aeronautics and Space Administration ( NASA ) and the military space programs to the individual services. This allowed ARPA to concentrate its efforts on the Project Defender (defense against ballistic missiles), Project Vela (nuclear test detection), and Project AGILE ( counterinsurgency R&D) programs, and to begin work on computer processing, behavioral sciences , and materials sciences. The DEFENDER and AGILE programs formed

1659-623: The Ramo-Wooldridge Corporation (later TRW) for the Lafayette class SSBNs. It was equipped with 8,192 words of 15-bit core memory plus parity bit , threaded by hand at their Canoga Park factory. Cycle time was about one microsecond . The AN/UYK-1 weighed about 550 pounds (250 kg). The AN/UYK-1 was a microprogrammed machine with a 15-bit word length that lacked hardware commands to subtract, multiply or divide, but could add, shift, form ones' complement , and test

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1738-529: The Ross Ice Shelf . Since no computer small enough to fit through a submarine's hatch existed (in 1958), a new computer was designed, named the AN/UYK-1 (TRW-130). It was built with rounded corners to fit through the hatch and was about five feet tall and sealed to be waterproof. The principal design engineer was then-UCLA-faculty-member Lowell Amdahl, brother of Gene Amdahl . The AN/UYK-1 was built by

1817-672: The personal computer and the internet on the list of innovations for which DARPA can claim at least partial credit." Its track record of success has inspired governments around the world to launch similar research and development agencies. DARPA is independent of other military research and development and reports directly to senior Department of Defense management. DARPA comprises approximately 220 government employees in six technical offices, including nearly 100 program managers, who together oversee about 250 research and development programs. The agency's current director, appointed in March 2021,

1896-634: The 1970s, the Soviet Union started launching their own satellite navigation system Parus (military) / Tsikada (civilian), which is still in use today besides the next generation GLONASS . Some Soviet warships were equipped with Motorola NavSat receivers. The Transit system was made obsolete by the Global Positioning System (GPS), and ceased navigation service in 1996. Improvements in electronics allowed GPS receivers to effectively take several fixes at once, greatly reducing

1975-471: The AN/UYK-1 computer. The computer would also receive from the ship's inertial navigation system (SINS) a reading of latitude and longitude. Using this information the AN/UYK-1 ran a least squares algorithm and provided a location reading in about fifteen minutes. There were 41 satellites in the Transit series that were assigned the Transit name by NASA. Transit 3B demonstrated uploading programs into

2054-623: The Adaptive Suspension Vehicle (ASV) nicknamed the "Walker" at the Ohio State University , under a research contract from DARPA. The vehicle was 17 feet long, 8 feet wide, and 10.5 feet high, and had six legs to support its three-ton aluminum body, in which it was designed to carry cargo over difficult terrains. However, DARPA lost interest in the ASV, after problems with cold-weather tests. On February 4, 2004,

2133-818: The Agency was centered on information processing and aircraft-related programs, including the National Aerospace Plane (NASP) or Hypersonic Research Program. The Strategic Computing Program enabled DARPA to exploit advanced processing and networking technologies and to rebuild and strengthen relationships with universities after the Vietnam War . In addition, DARPA began to pursue new concepts for small, lightweight satellites ( LIGHTSAT ) and directed new programs regarding defense manufacturing, submarine technology, and armor/anti-armor. In 1981, two engineers, Robert McGhee and Kenneth Waldron, started to develop

2212-518: The Doppler curve, recursively moving the trial position until the trial Doppler curve 'most closely' matched the actual Doppler received from the satellite for all two-minute curve segments. If the receiver was also moving relative to the earth, such as aboard a ship or airplane, this would cause mismatches with the idealized Doppler curves, and degrade position accuracy. However, positional accuracy could usually be computed to within 100 meters for

2291-482: The Doppler shift. If the satellite passes directly overhead, its angular velocity as it passes will be more than if it passes to one side. In the extreme case, with a satellite near the horizon, the relative velocity change is minimized. Thus the rapidity of the change in frequency is an indication of the relative longitude between the station and the satellite. Additionally, the rotation of the Earth provided another Doppler correction which could be used to determine whether

2370-584: The Geoceiver location. A Geoceiver was permanently located at the South Pole Station and operated by United States Geological Survey personnel. Since it was located on the surface of a moving ice sheet, its data was used to measure the ice sheet movement. Other Geoceivers were taken out in the field in Antarctica during the summer and were used to measure locations, for example the movement of

2449-557: The LEO region near their lowest altitude (or perigee ) but are not in a LEO orbit because their highest altitude (or apogee ) exceeds 2,000 km (1,243 mi). Sub-orbital objects can also reach the LEO region but are not in a LEO orbit because they re-enter the atmosphere . The distinction between LEO orbits and the LEO region is especially important for analysis of possible collisions between objects which may not themselves be in LEO but could collide with satellites or debris in LEO orbits. The mean orbital velocity needed to maintain

Transit (satellite) - Misplaced Pages Continue

2528-476: The Scout launch capacity to the Transit orbit was about 120 pounds (54 kg), which was later increased significantly. A satellite mass reduction had to be achieved, despite a demand for more power than APL had previously designed into a satellite. The second problem concerned the increased vibration that affected the payload during launching because the Scout used solid rocket motors. Thus, electronic equipment that

2607-559: The Transit satellites were chosen to cover the entire Earth; they crossed over the poles and were spread out at the equator. Since only one satellite was usually visible at any given time, fixes could be made only when one of the satellites was above the horizon. At the equator this delay between fixes was several hours; at mid-latitudes the delay decreased to an hour or two. For its intended role as an updating system for SLBM launch, Transit sufficed, since submarines took periodic fixes to reset their inertial guidance system , but Transit lacked

2686-453: The ability to provide high-speed, real-time position measurements. With later improvements, the system provided single-pass accuracy of roughly 200 metres (660 ft), and also provided time synchronization to roughly 50 microseconds. Transit satellites also broadcast encrypted messages, although this was a secondary function. The Transit satellites used arrays of magnetic-core memory as mass data storage up to 32 kilobytes. Determining

2765-649: The agency shut down its so called "LifeLog Project". The project's aim would have been, "to gather in a single place just about everything an individual says, sees or does". On October 28, 2009, the agency broke ground on a new facility in Arlington County, Virginia a few miles from The Pentagon . In fall 2011, DARPA hosted the 100-Year Starship Symposium with the aim of getting the public to start thinking seriously about interstellar travel. On June 5, 2016, NASA and DARPA announced that it planned to build new X-planes with NASA 's plan setting to create

2844-498: The agency's research portfolio, and two additional offices that manage special projects. All offices report to the DARPA director, including: A 1991 reorganization created several offices which existed throughout the early 1990s: A 2010 reorganization merged two offices: A list of DARPA's active and archived projects is available on the agency's website. Because of the agency's fast pace, programs constantly start and stop based on

2923-502: The arithmetic registers – for example, complementing the contents of one register while loading or storing another. It may have been the first computer that implemented a single-cycle indirect addressing ability. During a satellite pass, a GE receiver would receive the orbital parameters and encrypted messages from the satellite, as well as measure the Doppler-shifted frequency at intervals and provide this data to

3002-433: The atmosphere. The effects of adding such quantities of vaporized metals to Earth's stratosphere are potentially of concern but currently unknown. The LEO environment is becoming congested with space debris because of the frequency of object launches. This has caused growing concern in recent years, since collisions at orbital velocities can be dangerous or deadly. Collisions can produce additional space debris, creating

3081-474: The carry bit. Instructions to perform standard fixed and floating point operations were software subroutines and programs were lists of links and operators to those subroutines. For example, the "subtract" subroutine had to form the ones' complement of the subtrahend and add it. Multiplication required successive shifting and conditional adding. In the AN/UYK-1 instruction set, the machine-language instructions had two operators that could simultaneously manipulate

3160-656: The complexity of deducing a position. GPS uses many more satellites than were used with Transit, allowing the system to be used continuously, while Transit provided a fix only every hour or more. After 1996, the satellites were kept in use for the Navy Ionospheric Monitoring System (NIMS). The satellites (known as OSCAR or NOVA satellites) used in the system were placed in low polar orbits , at an altitude of about 600 nautical miles (690 mi; 1,100 km), with an orbital period of about 106 minutes. A constellation of five satellites

3239-548: The data to 5-hole paper tape. This data was sent to the Satellite Control Center at Applied Physics Laboratory in Laurel, Maryland using commercial and military teleprinter networks. The data from the fixed ground stations provided the location information on the Transit satellite orbit. Locating a Transit satellite in earth orbit from a known ground station using the Doppler shift is simply the reverse of using

Transit (satellite) - Misplaced Pages Continue

3318-455: The denser part of the atmosphere and below the inner Van Allen radiation belt . They encounter atmospheric drag from gases in the thermosphere (approximately 80–600 km above the surface) or exosphere (approximately 600 km or 400 mi and higher), depending on orbit height. Satellites in orbits that reach altitudes below 300 km (190 mi) decay quickly due to atmospheric drag. Equatorial low Earth orbits ( ELEO ) are

3397-459: The early explorers' discoveries. TRANSIT, sponsored by the Navy and developed under the leadership of Richard Kirschner at Johns Hopkins, was the first satellite positioning system." During the late 1960s, with the transfer of these mature programs to the Services, ARPA redefined its role and concentrated on a diverse set of relatively small, essentially exploratory research programs. The agency

3476-495: The farthest in LEO, before medium Earth orbit (MEO), have an altitude of 2,000 kilometers, about one-third of the radius of Earth and near the beginning of the inner Van Allen radiation belt . The term LEO region is used for the area of space below an altitude of 2,000 km (1,200 mi) (about one-third of Earth's radius). Objects in orbits that pass through this zone, even if they have an apogee further out or are sub-orbital , are carefully tracked since they present

3555-647: The first generation of Starlink satellites used polar orbits which provide coverage everywhere on Earth. Later Starlink constellations orbit at a lower inclination and provide more coverage for populated areas. Higher orbits include medium Earth orbit (MEO), sometimes called intermediate circular orbit (ICO), and further above, geostationary orbit (GEO). Orbits higher than low orbit can lead to early failure of electronic components due to intense radiation and charge accumulation. In 2017, " very low Earth orbits " ( VLEO ) began to be seen in regulatory filings. These orbits, below about 450 km (280 mi), require

3634-579: The first scientist to administer ARPA, managed to raise its budget to $ 250 million. It was Ruina who hired J. C. R. Licklider as the first administrator of the Information Processing Techniques Office , which played a vital role in creation of ARPANET , the basis for the future Internet. Additionally, the political and defense communities recognized the need for a high-level Department of Defense organization to formulate and execute R&D projects that would expand

3713-428: The first worldwide timekeeping service, allowing clocks everywhere to be synchronised with 50 microsecond accuracy. Calculating the most likely receiver location was not a trivial exercise. The navigation software used the satellite's motion to compute a 'trial' Doppler curve, based on an initial 'trial' location for the receiver. The software would then perform a least squares curve fit for each two-minute section of

3792-533: The foundation of DARPA sensor, surveillance , and directed energy R&D, particularly in the study of radar , infrared sensing, and x-ray / gamma ray detection. ARPA at this point (1959) played an early role in Transit (also called NavSat) a predecessor to the Global Positioning System (GPS). "Fast-forward to 1959 when a joint effort between DARPA and the Johns Hopkins Applied Physics Laboratory began to fine-tune

3871-545: The frontiers of technology and science, often beyond immediate U.S. military requirements. The name of the organization first changed from its founding name, ARPA, to DARPA, in March 1972, changing back to ARPA in February 1993, then reverted to DARPA in March 1996. The Economist has called DARPA "the agency that shaped the modern world," with technologies like " Moderna's COVID-19 vaccine ... weather satellites , GPS , drones , stealth technology , voice interfaces ,

3950-604: The frontiers of technology beyond the immediate and specific requirements of the Military Services and their laboratories. In pursuit of this mission, DARPA has developed and transferred technology programs encompassing a wide range of scientific disciplines that address the full spectrum of national security needs. From 1958 to 1965, ARPA's emphasis centered on major national issues, including space, ballistic missile defense , and nuclear test detection. During 1960, all of its civilian space programs were transferred to

4029-404: The ground station its signals will be shifted up in frequency, and as it recedes they will shift down again. The precise moment when the frequency is exactly equal to the broadcast frequency is when the satellite's ground track passes the ground location's location (with some corrections). This provides one of the two measurements needed. For the second measure, one has to consider the pattern of

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4108-433: The ground station was called a Geoceiver and was used to make field measurements. This receiver, power supply, punched tape unit, and antennas could fit in a number of padded aluminum cases and could be shipped as extra cargo on an airline. Data was taken over a period of time, typically a week, and sent back to the Satellite Control Center for processing. Therefore, unlike GPS, there was not an immediate accurate location of

4187-401: The known location of the satellite in orbit to locate an unknown location on the earth, again using the Doppler shift. A typical ground station occupied a small Quonset hut . The accuracy of the ground station measurements was a function of the ground station master clock accuracy. Initially a quartz oscillator in a temperature controlled oven was used as the master clock. The master clock

4266-468: The location of the satellite while it was measuring the shifts. The orbit ephemeris and clock corrections were uploaded twice each day to each satellite from one of the four Navy tracking and injection stations. The Transit satellite broadcast on 150 and 400 MHz. The two frequencies were used to allow the refraction of the satellite radio signals by the ionosphere to be canceled out, thereby improving location accuracy. The Transit system also provided

4345-638: The needs of the U.S. government. Structured information about some of the DARPA's contracts and projects is publicly available. DARPA is well known as a high-tech government agency, and as such has many appearances in popular fiction. Some realistic references to DARPA in fiction are as "ARPA" in Tom Swift and the Visitor from Planet X (DARPA consults on a technical threat), in episodes of television program The West Wing (the ARPA-DARPA distinction),

4424-646: The next year. Victoria Coleman became the director of DARPA in November 2020. In recent years, DARPA officials have contracted out core functions to corporations. For example, during fiscal year 2020, Chenega ran physical security on DARPA's premises, System High Corp. carried out program security, and Agile Defense ran unclassified IT services. General Dynamics runs classified IT services. Strategic Analysis Inc. provided support services regarding engineering, science, mathematics, and front office and administrative work. DARPA has six technical offices that manage

4503-579: The onboard computer's memory whilst in orbit. Transit 4A , launched June 29, 1961, was the first satellite to use a radioactive power source (RTG) (a SNAP-3 ). Transit 4B (1961) also had a SNAP-3 RTG. Transit 4B was among several satellites which were inadvertently damaged or destroyed in a nuclear explosion, specifically the United States Starfish Prime high-altitude nuclear test on July 9, 1962 and subsequent radiation belt . Transit 5A3 and Transit 5B-1 (1963) each had

4582-426: The orbit. Even for circular orbits , the altitude above ground can vary by as much as 30 km (19 mi) (especially for polar orbits ) due to the oblateness of Earth's spheroid figure and local topography . While definitions based on altitude are inherently ambiguous, most of them fall within the range specified by an orbit period of 128 minutes because, according to Kepler's third law , this corresponds to

4661-699: The purpose of forming and executing research and development projects to expand the frontiers of technology and science, and able to reach far beyond immediate military requirements. The two relevant acts are the Supplemental Military Construction Authorization ( Air Force ) (Public Law 85-325) and Department of Defense Directive 5105.15, in February 1958. It was placed within the Office of the Secretary of Defense (OSD) and counted approximately 150 people. Its creation

4740-488: The radio signals that would likely be emanating from the satellite. They were able to determine Sputnik's orbit by analyzing the Doppler shift of its radio signals during a single pass . Discussing the way forward for their research, their director Frank McClure, the chairman of APL's Research Center, suggested in March 1958 that if the satellite's position were known and predictable, the Doppler shift could be used to locate

4819-653: The robot . DARPA also supported the early development of both hypertext and hypermedia . DARPA funded one of the first two hypertext systems, Douglas Engelbart 's NLS computer system, as well as The Mother of All Demos . DARPA later funded the development of the Aspen Movie Map , which is generally seen as the first hypermedia system and an important precursor of virtual reality . The Mansfield Amendment of 1973 expressly limited appropriations for defense research (through ARPA/DARPA) only to projects with direct military application. The resulting " brain drain "

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4898-483: The rocket, but otherwise it was not successful because of trouble with the power system. Transit 5A-2 , launched on 5 April 1963, failed to achieve orbit. Transit 5A-3 , with a redesigned power supply, was launched on 15 June 1963. A malfunction of the memory occurred during powered flight that kept it from accepting and storing the navigation message, and the oscillator stability was degraded during launch. Thus, 5A-3 could not be used for navigation. However, this satellite

4977-462: The satellite was to the east or west of the ground station. These measurements produce a relative location compared to the satellite. To determine the actual location, that relative measure is applied to the location of the satellite. This is provided by periodically sending out precise time hacks (every two minutes), plus the satellite's six orbital elements and orbit perturbation variables. The ground receiver downloaded these signals and calculated

5056-451: The satellites within their orbits using the same principles. The satellite location data was used to collect orbital drag data, including variations in the upper atmosphere and the Earth's gravitational field. Beacon Explorer-A and Beacon Explorer-B also carried Transit-compatible transmitters. List of Transit satellites: Other Transit navigation satellites: DARPA The Defense Advanced Research Projects Agency ( DARPA )

5135-677: The successful programs were transitioned to the Services, such as the foundation technologies in automatic target recognition , space-based sensing, propulsion, and materials that were transferred to the Strategic Defense Initiative Organization (SDIO), later known as the Ballistic Missile Defense Organization (BMDO), now titled the Missile Defense Agency (MDA). During the 1980s, the attention of

5214-436: The system entered Naval service in 1964. A fully operational constellation of 36 satellites was in place in 1968. The Chance Vought/LTV Scout rocket was selected as the dedicated launch vehicle for the program because it delivered a payload into orbit for the lowest cost per pound. However, the Scout decision imposed two design constraints. First, the weight of the earlier satellites was about 300 pounds (140 kg) each, but

5293-460: The television program Numb3rs , and the Netflix film Spectral . Low Earth orbit A low Earth orbit ( LEO ) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, peaking in number at an altitude around 800 km (500 mi), while

5372-410: The transmitter is on the ground and the receiver is in orbit. ELTs measure the Doppler shift of the transmitter on the boat or aircraft as it passes overhead and forwards that data to the ground where the location of the craft can be determined. A network of ground stations, whose locations were accurately known, continually tracked the Transit satellites. They measured the Doppler shift and transferred

5451-412: The use of novel technologies for orbit raising because they operate in orbits that would ordinarily decay too soon to be economically useful. A low Earth orbit requires the lowest amount of energy for satellite placement. It provides high bandwidth and low communication latency . Satellites and space stations in LEO are more accessible for crew and servicing. Since it requires less energy to place

5530-634: Was McMurdo Station, Antarctica. For many years during the 1970s this station was staffed by a graduate student and an undergraduate student, typically in electrical engineering, from the University of Texas at Austin. Other stations were located at New Mexico State University, the University of Texas at Austin, Sicily, Japan, Seychelles Island, Thule Greenland and a number of other locations. The Greenland and Antarctica stations saw every pass of every Transit satellite because of their near pole location for these polar orbiting satellites. A portable version of

5609-455: Was checked daily for drift using a VLF receiver tuned to a US Navy VLF station. The VLF signal had the property that the phase of the VLF signal did not change from day to day at noon along the path between the transmitter and the receiver and thus could be used to measure oscillator drift. Later rubidium and cesium beam clocks were used. Ground stations had number names; for example, Station 019

5688-496: Was directly attributed to the launching of Sputnik and to U.S. realization that the Soviet Union had developed the capacity to rapidly exploit military technology. Initial funding of ARPA was $ 520 million. ARPA's first director, Roy Johnson, left a $ 160,000 management job at General Electric for an $ 18,000 job at ARPA. Herbert York from Lawrence Livermore National Laboratory was hired as his scientific assistant. Johnson and York were both keen on space projects, but when NASA

5767-452: Was established later in 1958 all space projects and most of ARPA's funding were transferred to it. Johnson resigned and ARPA was repurposed to do "high-risk", "high-gain", "far out" basic research, a posture that was enthusiastically embraced by the nation's scientists and research universities. ARPA's second director was Brigadier General Austin W. Betts, who resigned in early 1961 and was succeeded by Jack Ruina who served until 1963. Ruina,

5846-404: Was only one satellite visible at any time. Some other method of determining a second measurement was needed. Transit did this by measuring the signal's Doppler shift. The spacecraft traveled at about 17,000 mph (27,000 km/h), which could increase or decrease the frequency of the received carrier signal by as much as 10 kHz as measured on the ground. While the satellite is approaching

5925-573: Was renamed the Defense Advanced Research Projects Agency (DARPA) in 1972, and during the early 1970s, it emphasized direct energy programs, information processing, and tactical technologies. Concerning information processing, DARPA made great progress, initially through its support of the development of time-sharing . All modern operating systems rely on concepts invented for the Multics system, developed by

6004-461: Was required to provide reasonable global coverage. While the system was operational, at least ten satellites – one spare for each satellite in the basic constellation – were usually kept in orbit. Note that these OSCAR satellites were not the same as the OSCAR series of satellites that were devoted to use by amateur radio operators to use in satellite communications . The orbits of

6083-415: Was smaller than before and rugged enough to withstand the increased vibration of launch had to be produced. Meeting the new demands was more difficult than expected, but it was accomplished. The first prototype operational satellite ( Transit 5A-1 ) was launched into a polar orbit by a Scout rocket on 18 December 1962. The satellite verified a new technique for deploying the solar panels and for separating from

6162-454: Was the first to achieve gravity-gradient stabilization , and its other subsystems performed well. Surveyors used Transit to locate remote benchmarks by averaging dozens of Transit fixes, producing sub-meter accuracy. In fact, the elevation of Mount Everest was corrected in the late 1980s by using a Transit receiver to re-survey a nearby benchmark. Thousands of warships, freighters and private watercraft used Transit from 1967 until 1991. In

6241-400: Was typically less than 20 meters, (i.e. the accuracy was between that of LORAN C and GPS) For a typical 12 - 15 minute high satellite altitude pass accuracy was under ten meters. Certainly, Transit was the most accurate navigation system of its day. The basic operating principle of Transit is similar to the system used by emergency locator transmitters (ELTs), except that in the latter case

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