SPACETRACK
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The SPACETRACK program represents a worldwide Space Surveillance Network (SSN) of dedicated, collateral, and contributing electro-optical, passive radio frequency (rf) and radar sensors. The SSN is tasked to provide space object cataloging and identification, satellite attack warning, timely notification to U.S. forces of satellite fly-over, space treaty monitoring, and scientific and technical intelligence gathering. The continued increase in satellite and orbital debris populations, as well as the increasing diversity in launch trajectories, non-standard orbits, and geosynchronous altitudes, necessitates continued modernization of the SSN to meet existing and future requirements and ensure their cost-effective supportability. [1]
SPACETRACK also developed the systems interfaces necessary for the command and control, targeting, and damage assessment of a potential future U.S. Anti-satellite (ASAT) system. There is an Image Information Processing Center and Supercomputing facility at the Air Force Maui Optical Station (AMOS). The resources and responsibility for the HAVE STARE Radar System development were transferred to SPACETRACK from an intelligence program per Congressional direction in FY93.
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[edit] Early Methods: 1957–1963
The first formalized effort to catalog satellites occurred at the National Space Surveillance Control Center (NSSCC) located at Hanscom Field in Bedford, Massachusetts. The procedures used at the NSSCC were first reported in 1959 by Wahl, who was the technical director of the NSSCC. In 1960, under Project SPACETRACK, Fitzpatrick and Findley developed detailed documentation of the procedures used at the NSSCC. [2]
Observation of satellites was performed at more than 150 individual sites. Contributions came from radars, Baker–Nunn cameras, telescopes, radio receivers, and Operation Moonwatch participants. These dedicated individuals took observations on satellites by visual means. There are numerous observation types and sources. The observations were transferred to the NSSCC by teletype, telephone, mail, and personal messenger. There a duty analyst reduced the data and determined corrections that should be made to the orbital elements before they were used for further prediction. After this analysis, these corrections were fed into an IBM-709 computer that computed the updated orbital data. These updated orbital data were then used in another phase of the same computer program to yield the geocentric ephemeris. From the geocentric ephemeris, three different products were computed and sent back to the observing stations for their planning of future observing opportunities. [2]
[edit] Missile Warning and Space Surveillance in the Eisenhower Years
The launch of Sputnik I triggered a need for tracking of objects in space using the Space Tracking System. The first US system, Minitrack, was already in existence at the time of the Sputnik launch, but the US quickly discovered that Minitrack could not reliably detect and track satellites. The US Navy designed Minitrack to track the Vanguard satellite, and so long as satellites followed the international agreement on satellite transmitting frequencies, Minitrack could track any satellite. However, the Soviets chose not to use the international satellite frequencies. Thus, a major limitation of this system became visible. Minitrack could not detect or track an uncooperative or passive satellite. [3]
Concurrent with Minitrack was the use of the Baker-Nunn satellite tracking cameras. These systems used modified Schmidt telescopes of great resolution to photograph and identify objects in space. The cameras first became operational in 1956 and eventually operated at sites worldwide. The Air Force ran five sites, the Royal Canadian Air Force ran two, and the Smithsonian Institution's Astrophysics Observatory operated a further eight sites. The Baker-Nunn system, like Minitrack, provided little real-time data and was limited to night, clear weather operations. [3]
Beyond the problems in acquiring data on satellites, it became obvious that the US tracking network would soon be overwhelmed by the tremendous number of satellites that followed Sputnik and Vanguard. The huge amounts of satellite tracking data accumulated required creation or expansion of organizations and equipment just to sift through and catalog the objects. The need for real-time detection and tracking information to deal with Soviet satellite launches led on 19 December 1958 to ARPA's implementation of Executive Order 50-59 to establish a spacetrack network. This spacetrack network, Project Shepherd, began with the Space Track Filter Center at Bedford, Massachusetts, and an operational space defense network (i.e., a missile warning network). ARDC took up the spacetrack mission in late 1959 and in April 1960 set up the Interim National Space Surveillance Control Center at Hanscom Field, Massachusetts, to coordinate observations and maintain satellite data.(96) At the same time, DOD designated the Aerospace Defense Command (ADCOM), formerly Air Defense Command, as the prime user of spacetrack data. ADCOM formulated the first US plans for space surveillance. [3]
[edit] The US Space Catalog
The United States Department of Defense (DoD) has maintained a database of satellite states since the launch of the first Sputnik in 1957, known as the Space Object Catalog, or simply the Space Catalog. These satellite states are regularly updated with observations from the Space Surveillance Network, a globally distributed network of interferometer, radar and optical tracking systems. Two separate catalog databases are maintained under the US Space Command: a primary catalog by the Air Force Space Command (AFSPC), and an alternate catalog by the Naval Space Command (NSC). The number of cataloged objects is more than 10,000. [4,5,6]
Different astrodynamic theories are used to maintain these catalogs. The so-called General Perturbations (GP) theory provides a general analytical solution of the satellite equations of motion. The orbital elements and their associated partial derivatives are expressed as series expansions in terms of the initial conditions of these differential equations. The GP theories operated efficiently on the earliest electronic computing machines, and were therefore adopted as the primary theory for Space Catalog orbit determination. Assumptions must be made to simplify these analytical theories, such as truncation of the Earth’s gravitational potential to a few zonal harmonic terms. The atmosphere is usually modeled as a static, spherical density field that exponentially decays5. Third body influences and resonance effects are partially modeled6. Increased accuracy of GP theory usually requires significant development efforts. [4]
NASA maintains civilian databases of GP orbital elements, also known as NASA or NORAD two-line elements. The GP element sets are "mean" element sets that have specific periodic features removed to enhance long-term prediction performance, and require special software to reconstruct the compressed trajectory. [4]
[edit] Shemya and Diyarbakir Radar Sites
AN/FPS-17 and AN/FPS-80 radars placed at Shemya in the 1960s to track Soviet missile tests and to support the Air Force Spacetrack System. In July 1973, Raytheon won a contract to build a system called "Cobra Dane" on Shemya Island in the Aleutian Islands off the Alaskan coast. Designated as the AN/FPS-108, Cobra Dane replaced AN/FPS-17 and AN/FPS-80 radars. Becoming operational in 1977, Cobra Dane also had a primary mission of monitoring Soviet tests of missiles launched from southwest Russia aimed at the Siberian Kamchatka peninsula. This large, single-faced, phased-array radar was the most powerful ever built.
The FPS-80 was a tracking radar and the FPS-17 was a detection radar for Soviet missiles. Both were part of the Ballistic Missile Early Warning System (BMEWS). The large detection radar (AN/FPS-17) went into operation in 1960. In 1961, the AN/FPS-80 tracking radar was constructed nearby. These radars were closed in the 1970s.
The Pirinclik (near Diyarbakir, Turkey) intelligence collection radar consisted of one detection radar and one tracking radar. The Pirinclik radar is operated by the 19th Surveillance Squadron. The radar reached IOC on 1 June 1955. The Pirinclik Radar Site consisted of a detection radar (AN/FPS-17) and a mechanical tracking radar (AN/FPS-79). Both radars operated at a UHF (432 MHz) frequency. Although limited by their mechanical technology, Pirinclik's two radars give the advantage of tracking two objects simultaneously in real time. Its location close to the southern FSU makes it the only ground sensor capable of tracking actual deorbits of Russian space objects. In addition, the Pirinclik radar was the only 24-hour-per-day eastern hemisphere deep space sensor. Radar operations at Pirinclik were terminated in March 1997,
[edit] AN/FPS-17
With the Soviet Union apparently making rapid progress in its rocket program, in 1954 the United States began a program to develop a tracking radar. General Electric Heavy Military Electronics Division in Syracuse, NY was the prime contractor and Lincoln Laboratory was the subcontractor. This tracking radar, the AN/FPS-17, was conceived, designed, built, and installed for operation in less than two years. Installed at Laredo AFB in Texas, the first AN/FPS-17 was used to track rockets launched from White Sands, New Mexico. The radar was unique; it featured a fixed-fence antenna that stood 175 feet high and 110 feet wide. The transmitter sent out ash pulse at a frequency between 180 to 220 MHz. Units were installed in the late 1950s at Shemya Island in the Aleutians and in Diyarbakir (Pirinclik), Turkey. The AN/FPS-17 Detection Radar on Shemya became operational in May 1960. The unit at Shemya subsequently was replaced by the Cobra Dane (AN/FPS-108) radar. (Jane’s Radar and Electronic Systems, 6th edition, Bernard Blake, ed. (1994), p. 78.)
There were two AN/FPS-17 detection radars at Diyarbakir, Turkey and three more at Shemya in the Aleutians.
[edit] AN/FPS-79
The FPS-79 at Diyarbakir has a unique feature which enhances its Spacetrack usefulness. A variable-focus feed horn provides a wide beam for detection and a narrow beamwidth for tracking. Pulse compression is used to improve both the gain and resolution of the 35-foot dish antenna. Steering is mechanical; the FPS-79 has a range of 24,000 miles.
After circling the Earth in an apparently dormant state for 9 months, on November 13, 1986 the SPOT 1 Ariane third stage violently separated into some 465 detectable fragments - the most severe satellite breakup yet recorded prior to 2007.
Although the debris clous did not pass over the continental United States until more than 8 hours later, personnel in the Space Surveillance Center (SSC) at the Cheyenne Mountain Complex in Colorado Springs, Colorado reported that the U.S. FPS-79 radar at Pirinclik, Turkey, noticed the debris within minutes of the fragmentation. (N.L. Johnson, Preliminary analysis of the fragmentation of the SPOT 1 Ariane Third Stage, chapter 4 in J.P. Loftus, Orbital Debris from Upper Stage Breakup, Vol 121, Progress in Astronautics and Aeronautics, AIAA, Washington, DC, 1989, pp. 41-47).
[edit] Blue Nine and Blue Fox
Blue Nine refers to a project which produced the AN/FPS-79 Tracking Radar Set built by General Electric, used with the 466L Electromagnetic Intelligence System (ELINT); US Air Force. Blue Fox refers to a modification of the AN/FPS-80 tracking radar to the AN/FPS-80(M) configuration. Shemya, AK, 1964. Both of these systems incorporated GE M236 computers.
[edit] AN/FPS-80
Built by General Electric. Used as tracker radar for Spacetrack network measurements once target detected. One sited at Sheyma. Principally used for intelligence purposes to track Russian missiles.
[edit] References
- C. Coombs. SPACETRACK - Watchdog of the skies. William Morrow & Co., New York, 1969, 128 pp.
- Felix R. Hoots ; Paul W. Schumacher Jr.; Robert A. Glover. History of Analytical Orbit Modeling in the U. S. Space Surveillance System. Journal of Guidance, Control, and Dynamics, AIAA Doc. No. 0731-5090 vol.27 no.2 (174-185), 2004.
- Maj Michael J. Muolo, et al. AU-18 Space Handbook - A War Fighter's Guide to Space, Volume One, Air University Press, Maxwell Air Force Base, Alabama 36112-6428, December 1993[1].
- Neal, H.L., S.L. Coffey, S.H. Knowles, “Maintaining the Space Object Catalog with Special Perturbations.” AAS 97-687, AAS/AIAA Astrodynamics Meeting, Sun Valley, ID, Aug 4-7, 1997 (Astrodynamics 1997 v.97 Part II, pp.1349-1360).
- Vallado, D.A., Fundamentals of Astrodynamics and Applications. McGraw-Hill, 1997. pp. 654 - 657.
- Felix R. Hoots and Ronald L. Roehrich. SPACETRACK REPORT NO. 3 - Models for Propagation of NORAD Element Sets, December 1980 (Package Compiled by TS Kelso, 31 December 1988). Published by: Project Spacetrack Reports, Office of Astrodynamics, Aerospace Defense Center ADC/DO6, Peterson AFB CO 80914.
