The United States Space Surveillance Network (SSN) detects, tracks, catalogs and identifies artificial objects
orbiting Earth, e.g. active/inactive
satellite
A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...
s, spent
rocket
A rocket (from , and so named for its shape) is a vehicle that uses jet propulsion to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely ...
bodies, or
fragmentation debris. The system is the responsibility of
United States Space Command
United States Space Command (USSPACECOM or SPACECOM) is a unified combatant command of the United States Department of Defense, responsible for military operations in outer space, specifically all operations 100 kilometers (62 miles) and greater ...
and operated by the
United States Space Force
The United States Space Force (USSF) is the space force branch of the United States Department of Defense. It is one of the six United States Armed Forces, armed forces of the United States and one of the eight uniformed services of the Unite ...
and its functions are:
* Predict when and where a
decaying space object will
re-enter the
Earth's atmosphere
The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weathe ...
;
* Prevent a returning space object, which to
radar
Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...
looks like a missile, from triggering a
false alarm
A false alarm, also called a nuisance alarm, is the deceptive or erroneous report of an emergency, causing unnecessary panic and/or bringing resources (such as emergency services) to a place where they are not needed. False alarms may occur with ...
in missile-attack warning sensors of the U.S. and other countries;
* Chart the present position of space objects and plot their anticipated orbital paths;
* Detect new artificial objects in space;
* Correctly map objects traveling in
Earth orbit;
* Produce a running catalog of artificial space objects;
* Determine ownership of a re-entering space object;
*
The Space Surveillance Network includes dedicated, collateral, and contributing electro-optical, passive radio frequency (RF) and radar sensors. It provides 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
Technical intelligence (TECHINT) is intelligence about weapons and equipment used by the armed forces of foreign nations. The related term, scientific and technical intelligence, addresses information collected or analyzed about the broad range ...
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.
SPACETRACK also developed the systems interfaces necessary for the command and control, targeting, and damage assessment of a potential future U.S.
anti-satellite weapon
Anti-satellite weapons (ASAT) are space weapons designed to incapacitate or destroy satellites for Military strategy, strategic or Military tactics, tactical purposes. Although no ASAT system has been utilized in warfare, a few countries (China, ...
(ASAT) system. There is an Image Information Processing Center and Supercomputing facility at the
Air Force Maui Optical Station (AMOS).
History
1957–1963

The first formalized effort by the
US government
The Federal Government of the United States of America (U.S. federal government or U.S. government) is the national government of the United States.
The U.S. federal government is composed of three distinct branches: legislative, execut ...
to catalog satellites occurred at Project Space Track, later known as the National Space Surveillance Control Center (NSSCC), located at
Hanscom Field
Laurence G. Hanscom Field , commonly known as Hanscom Field, is a public use airport operated by the Massachusetts Port Authority, located outside Boston in Bedford, Massachusetts, United States.
Hanscom is mainly a general aviation airport, ...
in
Bedford, Massachusetts
Bedford is a town in Middlesex County, Massachusetts, United States. The population of Bedford was 14,161 at th2022 United States census
History
''The following compilation comes from Ellen Abrams (1999) based on information from Abram Engl ...
. The procedures used at the NSSCC were first reported in 1959 and 1960 by Wahl,
[Wahl, E]erhart Erhart is a surname and a given name. Notable people so named include:
* Gregor Erhart (c. 1470?–1540), German sculptor
* Maria Erhart (1944–2011), Austrian international bridge player
* Michel Erhart (c. 1440-45 — after 1522), German late ...
W., Program Development in Orbital Computation at the U.S. National Space Surveillance Control Center. roceedings of the Second Symposium (International) on Rockets and Astronautics okyo: May 1960./ref> who was the technical director of the NSSCC. In 1960, under Project Space Track, Fitzpatrick and Findley developed detailed documentation of the procedures used at the NSSCC. Project Space Track
Project Space Track was a research and development project of the US Air Force, to create a tracking system for all artificial satellites of the Earth and space probes, domestic and foreign.
Project Space Track was started in 1957 at the Air For ...
began its history of satellite tracking from 1957–1961.
Early Space Track observations of satellites were collected at more than 150 individual sites, including radar stations, Baker–Nunn cameras, telescopes, radio receivers, and by citizens participating in the Operation Moonwatch
Operation Moonwatch (also known as ''Project Moonwatch'' and, more simply, as ''Moonwatch'') was an amateur science program formally initiated by the Smithsonian Astrophysical Observatory (SAO) in 1956. The SAO organized Moonwatch as part of th ...
program. Individuals at these Moonwatch sites recorded observations of satellites by visual means, but there were numerous observation types and sources, some automated, some only semi-automated. 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 predictions. After this analysis, the corrections were fed into an IBM 709
The IBM 709 is a computer system that was announced by IBM in January 1957 and first installed during August 1958. The 709 was an improved version of its predecessor, the IBM 704, and was the third of the IBM 700/7000 series of scientific compute ...
computer that computed the updated orbital data. The updated orbital data were then used in another phase of the same computer program to yield the geocentric
In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center. Under most geocentric models, the Sun, Moon, stars, an ...
ephemeris
In astronomy and celestial navigation, an ephemeris (; ; , ) is a book with tables that gives the trajectory of naturally occurring astronomical objects and artificial satellites in the sky, i.e., the position (and possibly velocity) over tim ...
. From the geocentric ephemeris, three different products were computed and sent back to the observing stations for their planning of future observing opportunities.
Missile Warning and Space Surveillance in the Eisenhower Years
The launch of Sputnik 1
Sputnik 1 (, , ''Satellite 1''), sometimes referred to as simply Sputnik, was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space program ...
by the Soviet Union
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
led to a US government perceived need to better track objects in space using the Space Tracking System. The first US system, Minitrack
The Minitrack Network was the first U.S. satellite tracking network to become operational, in 1957. It was used to track the flights of Sputnik, Vanguard, Explorer, and other early space efforts. Minitrack was the progenitor of Spacecraft Tracki ...
, 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
The vanguard (sometimes abbreviated to van and also called the advance guard) is the leading part of an advancing military formation. It has a number of functions, including seeking out the enemy and securing ground in advance of the main force.
...
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.
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 1958 and eventually operated at sites worldwide. At their peak, the Air Force ran five sites, the Royal Canadian Air Force
The Royal Canadian Air Force (RCAF; ) is the air and space force of Canada. Its role is to "provide the Canadian Forces with relevant, responsive and effective airpower". The RCAF is one of three environmental commands within the unified Can ...
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
Real-time data (RTD) is information that is delivered immediately after collection. There is no delay in the timeliness of the information provided. Real-time data is often used for navigation or tracking. Such data is usually data processing, proc ...
and was additionally limited to night-time, clear weather operations.
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 amount of satellite tracking data accumulated required creation or expansion of organizations and equipment 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
Bedford is a town in Middlesex County, Massachusetts, United States. The population of Bedford was 14,161 at th2022 United States census
History
''The following compilation comes from Ellen Abrams (1999) based on information from Abram Engl ...
, 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
Laurence G. Hanscom Field , commonly known as Hanscom Field, is a public use airport operated by the Massachusetts Port Authority, located outside Boston in Bedford, Massachusetts, United States.
Hanscom is mainly a general aviation airport, ...
, Massachusetts
Massachusetts ( ; ), officially the Commonwealth of Massachusetts, is a U.S. state, state in the New England region of the Northeastern United States. It borders the Atlantic Ocean and the Gulf of Maine to its east, Connecticut and Rhode ...
, to coordinate observations and maintain satellite data. 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.
During the years that intercontinental ballistic missiles were developing as frontline weapon systems, numerous missile detection and warning sensors were being experimented with and fielded as operational sensors and most of these contributed satellite observation data at one time or another. Many have been overlooked by current histories and additional research is merited. Among these were two Trinidad detection and tracking radars; Laredo, Texas
Laredo ( ; ) is a city in the U.S. state of Texas and the county seat of Webb County, Texas, Webb County, on the north bank of the Rio Grande in South Texas, across from Nuevo Laredo, Tamaulipas, Mexico. Founded in 1755, Laredo grew from a villag ...
; and Moorestown, New Jersey
Moorestown is a Township (New Jersey), township in Burlington County, New Jersey, Burlington County in the U.S. state of New Jersey. It is an eastern suburb of Philadelphia and geographically part of the South Jersey region of the state. As of ...
. Additional sensors that performed or contributed to space tracking but are not yet included in this page include mechanical tracking radars on the islands of Kaena Point, Antigua
Antigua ( ; ), also known as Waladli or Wadadli by the local population, is an island in the Lesser Antilles. It is one of the Leeward Islands in the Caribbean region and the most populous island of the country of Antigua and Barbuda. Antigua ...
, Ascension Island
Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the Atlantic Ocean, South Atlantic Ocean. It is about from the coast of Africa and from the coast of South America. It is governed as part of the British Overs ...
, Naval Station San Miguel, and Kwajalein Atoll
Kwajalein Atoll (; Marshallese language, Marshallese: ) is part of the Marshall Islands, Republic of the Marshall Islands (RMI). The southernmost and largest island in the atoll is named Kwajalein Island, which its majority English-speaking re ...
; the three BMEWS
The RCA 474L Ballistic Missile Early Warning System (BMEWS, 474L System, Project 474L) was a United States Air Force Cold War early warning radar, computer, and communications system, for ballistic missile detection. The network of twelve radar ...
sites; the Pave Paws
PAVE PAWS (PAVE Phased Array Warning System) is a complex Cold War early warning radar and computer system developed in 1980 to "detect and characterize a sea-launched ballistic missile attack against the United States". The first solid-state ...
sites; the AN/FSS-7 missile warning radar sites; the Passive electronically scanned array
A passive electronically scanned array (PESA), also known as passive phased array, is an antenna in which the beam of radio waves can be electronically steered to point in different directions (that is, a phased array antenna), in which all the ...
sites; Cavalier, ND
Cavalier is the largest city in Pembina County, North Dakota, United States. It is the county seat of Pembina County. The population was 1,246 at the 2020 United States census, 2020 census. Cavalier was founded in 1875 and became the county seat ...
; Eglin, FL; Maui Space Surveillance System; Globus II; San Vito dei Normanni Air Station; TOS/CROSS; and 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 dev ...
.
Air Force Space Surveillance System
The Air Force Space Surveillance System
The AN/FPS-133 Air Force Space Surveillance System, colloquially known as the Space Fence, was a U.S. government multistatic radar system built to detect orbital objects passing over America. It is a component of the U.S. space surveillance ...
(AFSSS), also known as the "space fence", was a very high frequency radar network located at sites across the southern United States (from California
California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
to Georgia
Georgia most commonly refers to:
* Georgia (country), a country in the South Caucasus
* Georgia (U.S. state), a state in the southeastern United States
Georgia may also refer to:
People and fictional characters
* Georgia (name), a list of pe ...
) with a centralized data processing site at the Naval Network and Space Operations Command in Dahlgren, Virginia
Dahlgren is an unincorporated community and census-designated place (CDP) in King George County, Virginia, United States. The population was 2,946 at the time of the 2020 census, up from 2,653 at the 2010 census, and up from 997 in 2000.
Histor ...
. AFSSS began as the Navy's Space Surveillance (SPASUR) system in 1961 (later renamed NAVSPASUR). It was transferred to the Air Force in 2004 and renamed AFSSS. The "fence" was operated by the U.S. Air Force ( 20th Space Control Squadron Detachment 1).
The Satellite Detection and Reconnaissance Defense (the former designation of the NSSS) reached initial operating capability in 1961. The role of the "fence" grew. The system detected space objects from new launches, maneuvers of existing objects, breakups of existing objects, and provided data to users from its catalog of space objects. Orbital parameters of more than 10,000 objects were maintained in this catalog—which has now gained usage by NASA, weather agencies, and friendly foreign agencies. The information is essential to computing the collision avoidance information to de-conflict launch window
In the context of spaceflight, launch period is the collection of days, and launch window is the time period on a given day, during which a particular rocket
A rocket (from , and so named for its shape) is a vehicle that uses jet propulsio ...
s with known orbiting space objects.
The 21st Space Wing
The 21st Wing (21 WG) is an inactive wing of the United States Air Force.
It was established in 1953 as the 21st Fighter-Bomber Wing, deploying to Europe to join NATO's Allied Command Europe, before being inactivated in 1958. It reactivated i ...
closed the Air Force Space Surveillance System on 1 October 2013 citing resource constraints caused by sequestration. A new S-band Space Fence
The Space Fence is a second-generation space surveillance system operated by the United States Space Force in order to track artificial satellites and space debris in Earth orbit. It was constructed and designed by Lockheed Martin, Northrop Gr ...
is under construction at Kwajalein Atoll
Kwajalein Atoll (; Marshallese language, Marshallese: ) is part of the Marshall Islands, Republic of the Marshall Islands (RMI). The southernmost and largest island in the atoll is named Kwajalein Island, which its majority English-speaking re ...
.
US Space Catalog
The United States Department of Defense
The United States Department of Defense (DoD, USDOD, or DOD) is an United States federal executive departments, executive department of the federal government of the United States, U.S. federal government charged with coordinating and superv ...
(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. By the year 2001, the number of cataloged objects was nearly 20,000.
Different astrodynamics
Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to rockets, satellites, and other spacecraft. The motion of these objects is usually calculated from Newton's laws of motion and the Newton's law of univ ...
theories are used to maintain these catalogs. The General Perturbations (GP) theory provides a general analytical solution of the satellite equations of motion. The orbital elements and their associated partial derivative
In mathematics, a partial derivative of a function of several variables is its derivative with respect to one of those variables, with the others held constant (as opposed to the total derivative, in which all variables are allowed to vary). P ...
s are expressed as series expansion
In mathematics, a series expansion is a technique that expresses a Function (mathematics), function as an infinite sum, or Series (mathematics), series, of simpler functions. It is a method for calculating a Function (mathematics), function that ...
s 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 decays. Third body influences and resonance effects are partially modeled. Increased accuracy of GP theory usually requires significant development efforts.
NASA maintains civilian databases of GP orbital elements, also known as NASA or NORAD
North American Aerospace Defense Command (NORAD ; , CDAAN), known until March 1981 as the North American Air Defense Command, is a combined organization of the United States and Canada that provides aerospace warning, air sovereignty, and pr ...
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
A trajectory or flight path is the path that an object with mass in motion follows through space as a function of time. In classical mechanics, a trajectory is defined by Hamiltonian mechanics via canonical coordinates; hence, a complete tra ...
.
Shemya and Diyarbakir Radar Sites
AN/FPS-17 and AN/FPS-80 radars were placed at Shemya
Shemya or Simiya () is a small island in the Semichi Islands group of the Near Islands chain in the Aleutian Islands archipelago southwest of Alaska, at . It has a land area of , and is about southwest of Anchorage, Alaska. It is wide and long ...
Island in the Aleutian Islands off the Alaskan coast 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
The AN/FPS-108 COBRA DANE is a PESA phased array radar installation operated by Raytheon for the United States Space Force (originally for the United States Air Force) at Eareckson Air Station on the island of Shemya, Aleutian Islands, Alaska. ...
" on Shemya. 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 RCA 474L Ballistic Missile Early Warning System (BMEWS, 474L System, Project 474L) was a United States Air Force Cold War early warning radar, computer, and communications system, for ballistic missile detection. The network of twelve radar ...
). 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 Diyarbakır Air Station intelligence collection radar site ultimately consisted of one detection radar (FPS-17) and one mechanical tracking radar (FPS-79). The Pirinclik radars were operated by the 19th Surveillance Squadron. The FPS-17 radar reached IOC on 1 June 1955 and the FPS-79 in 1964. Both radars operated at a UHF (432 MHz) frequency. Although limited by their mechanical technology, Pirinclik's two radars gave the advantage of tracking two objects simultaneously in real time. Its location close to the southern Former Soviet Union
The post-Soviet states, also referred to as the former Soviet Union or the former Soviet republics, are the independent sovereign states that emerged/re-emerged from the dissolution of the Soviet Union in 1991. Prior to their independence, they ...
made 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.
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 long range surveillance radar. General Electric Heavy Military Electronics Division (HMED) in Syracuse, NY
Syracuse ( ) is a city in and the county seat of Onondaga County, New York, United States. With a population of 148,620 and a metropolitan area of 662,057, it is the fifth-most populated city and 13th-most populated municipality in the state o ...
was the prime contractor and 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 dev ...
was a subcontractor. This detection radar, the AN/FPS-17, was conceived, designed, built, and installed for operation in nine months.[''Progress In Defense and Space, A History of the Aerospace Group of the General Electric Company'', Major A. Johnson, 1993, pp262, 287-289.][''A Fiery Peace in a Cold War: Bernard Schriever and the Ultimate Weapon'', Neil Sheehan, 2009, pp301-311.]["The Diyarbakir Radar", Stanley G. Zabetakis & John F. Peterson, 1964. ''Studies in Intelligence'', Fall 1964 edition, pages 41-47. Declassified.] The first installation, designated AN/FPS-17(XW-1) was at Diyarbakir ( Pirinclik), Turkey, to detect Soviet launches. A second system, designated AN/FPS-17(XW-2), was installed at Laredo AFS (about northeast of Laredo AFB
Laredo Air Force Base, is a since-deactivated Undergraduate Pilot Training (UPT) installation of the Air Training Command (ATC) in Laredo, Texas
Laredo ( ; ) is a city in the U.S. state of Texas and the county seat of Webb County, Texas, Web ...
) in Texas, to track rockets launched from White Sands, New Mexico
White Sands is a census-designated place (CDP) in Doña Ana County, New Mexico, United States. It consists of the main residential area on the White Sands Missile Range. As of the 2010 census the population of the CDP was 1,651. It is part of ...
, and serve as a radar test bed. A third system, designated AN/FPS-17(XW-3), was installed on Shemya
Shemya or Simiya () is a small island in the Semichi Islands group of the Near Islands chain in the Aleutian Islands archipelago southwest of Alaska, at . It has a land area of , and is about southwest of Anchorage, Alaska. It is wide and long ...
Island, Alaska, to detect Soviet launches. The Diyarbakir FPS-17 became operational in June 1955, the Laredo installation in February 1956, and Shemya in May 1960. The first two installations closed without replacements; the Shemya installation was replaced by the Cobra Dane
The AN/FPS-108 COBRA DANE is a PESA phased array radar installation operated by Raytheon for the United States Space Force (originally for the United States Air Force) at Eareckson Air Station on the island of Shemya, Aleutian Islands, Alaska. ...
(AN/FPS-108) radar.
The FPS-17 antenna featured a fixed parabolic torus section reflector that typically stood high and wide and was illuminated by an array of radar feed horns placed in front of it. The transmitters operated in the VHF band, sending out pulses at frequencies between approximately 180 to 220 MHz.[NRL Memorandum Report 1637, "Information on Over-the-Horizon Radar", Part VI, 13 August 1965. Declassified.] The FPS-17 was unique in that, unlike most radar types, each site's version differed from the other sites. Differences included transmitter equipment, reflector size and number, and the number and arrangement of feed horns. Additionally, the FPS-17 was the first operational radar system to employ pulse compression techniques. There were two AN/FPS-17 antennas at Diyarbakir, Turkey, one antenna at Laredo, and three at Shemya
Shemya or Simiya () is a small island in the Semichi Islands group of the Near Islands chain in the Aleutian Islands archipelago southwest of Alaska, at . It has a land area of , and is about southwest of Anchorage, Alaska. It is wide and long ...
in the Aleutians
The Aleutian Islands ( ; ; , "land of the Aleuts"; possibly from the Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before 1867, the Catherine Archipelago—are a chain of 14 main, larger volcanic island ...
.
AN/FPS-79
The original FPS-79 antenna at Diyarbakir had a unique feature which enhanced its Spacetrack usefulness. A variable-focus feed horn provided a wide beam for detection and a narrow beamwidth for tracking. That antenna was replaced by a new antenna and pedestal in 1975. Pulse compression
Pulse compression is a signal processing technique commonly used by radar, sonar and Ultrasound, echography to either increase the range angular resolution, resolution when pulse length is constrained or increase the Signal-to-noise ratio, signal ...
was used to improve both the gain and resolution of the dish antenna. Steering was mechanical; the FPS-79 had a range of . The radar site closed in 1997.
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 cloud did not pass over the continental United States
The contiguous United States, also known as the U.S. mainland, officially referred to as the conterminous United States, consists of the 48 adjoining U.S. states and the District of Columbia of the United States in central North America. The te ...
until more than 8 hours later, personnel in the Space Surveillance Center (SSC) at the Cheyenne Mountain Complex
The Cheyenne Mountain Complex is a United States Space Force installation and defensive bunker located in unincorporated El Paso County, Colorado, next to the city of Colorado Springs, at the Cheyenne Mountain Space Force Station, which host ...
in Colorado Springs, Colorado
Colorado Springs is the most populous city in El Paso County, Colorado, United States, and its county seat. The city had a population of 478,961 at the 2020 United States census, 2020 census, a 15.02% increase since 2010 United States Census, 2 ...
reported that the U.S. FPS-79 radar at Pirinclik, Turkey, noticed the debris within minutes of the fragmentation.
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.
AN/FPS-80
A 60-foot dish mechanical tracking radar built by General Electric. Deployed at Shemya Island, Alaska, as a UHF radar and upgraded to L-Band in 1964. Used as tracker radar for Spacetrack network measurements once target detected. Principally used for intelligence purposes to track Russian missiles. The advanced FPS-108 Cobra Dane phased array radar replaced the FPS-17 and FPS-80 radars in 1977.
Space Surveillance Network
The command accomplishes these tasks through its Space Surveillance Network (SSN) of U.S. Army, Navy and Space Force operated, 30+ ground-based radars and optical telescopes worldwide, plus 6 satellites in orbit.
, the catalog built using SSN data listed 44,336 objects including 8,558 satellites launched into orbit since 1957. 17,480 of them were actively tracked while 1,335 were lost. The rest have re-entered Earth's turbulent atmosphere and disintegrated, or survived re-entry and impacted the Earth. The SSN typically tracks space objects which are 10 centimeters in diameter (baseball size) or larger.
The Space Surveillance Network has numerous sensors that provide data. They are separated in three categories: dedicated sensors, collateral sensors and auxiliary sensors. Both the dedicated and collateral sensors are operated by the USSPACECOM, but while the former have a primary objective to acquire SSN data, the latter obtain SSN data as a secondary objective. The auxiliary sensors are not operated by the USSPACECOM and usually perform space surveillance collaterally. Additionally sensors are classified as Near-Earth (NE) tracking - observing satellites, space debris
Space debris (also known as space junk, space pollution, space waste, space trash, space garbage, or cosmic debris) are defunct human-made objects in spaceprincipally in Earth orbitwhich no longer serve a useful function. These include dere ...
and other objects in lower orbits, or Deep Space (DS) - generally for asteroid
An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
s and comet
A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
s.
* Dedicated sensors
** Ground-based Electro-Optical Deep Space Surveillance (GEODSS) sites
** Space Surveillance Telescope
The Space Surveillance Telescope (SST) is a Southern Hemisphere-based United States Space Force telescope used for detecting, tracking, and cataloguing satellites, near-Earth objects, and space debris.
In 2011, SST achieved first light at the ...
(SST)
** MOSS - an Electro-Optical (E-O) surveillance system located at the Morón Air Base, Spain
Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
** GLOBUS II radar
** AN/FPS-85 Space Track Radar
** AN/FPS-133 Air Force Space Surveillance System, also known as the Space Fence and its replacement Space Fence
The Space Fence is a second-generation space surveillance system operated by the United States Space Force in order to track artificial satellites and space debris in Earth orbit. It was constructed and designed by Lockheed Martin, Northrop Gr ...
** Midcourse Space Experiment (MSX) / Space Based Visible (SBV) satellites
* Collateral sensors
** Maui Space Surveillance System (MSSS) and Advanced Electro-Optical System (AEOS) telescope, co-located with a GEODSS station in Maui
Maui (; Hawaiian language, Hawaiian: ) is the second largest island in the Hawaiian archipelago, at 727.2 square miles (1,883 km2). It is the List of islands of the United States by area, 17th-largest in the United States. Maui is one of ...
, Hawaii
Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...
** Haystack Ultrawideband Satellite Imaging Radar (HUSIR), Haystack Auxiliary Radar (HAX) and Millstone Hill Radar
** ALTAIR and ALCOR radars at the Ronald Reagan Ballistic Missile Defense Test Site
The Ronald Reagan Ballistic Missile Defense Test Site, commonly referred to as the Reagan Test Site (formerly Kwajalein Missile Range), is a missile test range in Marshall Islands (Pacific Ocean). It covers about and includes rocket launch s ...
, Kwajalein Atoll
Kwajalein Atoll (; Marshallese language, Marshallese: ) is part of the Marshall Islands, Republic of the Marshall Islands (RMI). The southernmost and largest island in the atoll is named Kwajalein Island, which its majority English-speaking re ...
** Ascension Range Radar, locate at the Eastern Spacelift Range
** Ground-Based Radar Prototype
The Ground-Based Radar Prototype (GBR-P) is an X-band mechanically slewed phased array radar system. It functions primarily as a fire control radar for national missile defence, ballistic missile defence. The radar is used for surveillance (autono ...
(GBR-P), located Ronald Reagan Ballistic Missile Defense Test Site, Kwajalein Atoll
* Auxiliary sensors
** Solid State Phased Array Radar System
The Solid State Phased Array Radar System (SSPARS), colloquially Ballistic Missile Early Warning System radar network (BMEWS radar network), is a United States Space Force radar, computer, and communications system for missile warning and space ...
(SSPARS) / AN/FPS-132 Upgraded Early Warning Radar
The Solid State Phased Array Radar System (SSPARS), colloquially Ballistic Missile Early Warning System radar network (BMEWS radar network), is a United States Space Force radar, computer, and communications system for missile warning and space ...
(UEWR) system of system, deployed at multiple sites
** AN/FPS-108 Cobra Dane
The AN/FPS-108 COBRA DANE is a PESA phased array radar installation operated by Raytheon for the United States Space Force (originally for the United States Air Force) at Eareckson Air Station on the island of Shemya, Aleutian Islands, Alaska. ...
** AN/FPQ-16 Perimeter Acquisition Radar Characterization System
A perimeter is the length of a closed boundary that encompasses, surrounds, or outlines either a two-dimensional shape or a one-dimensional line. The perimeter of a circle or an ellipse is called its circumference.
Calculating the perimeter ...
(PARCS)
Ground-based Electro-Optical Deep Space Surveillance
Ground-based Electro-Optical Deep Space Surveillance, or GEODSS, is an optical system that uses telescope
A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...
s, low-light level TV cameras, and computers. It replaced an older system of six Baker-Nunn cameras which used photographic film
Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin photographic emulsion, emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the ...
.
There are three operational GEODSS sites that report to the 20th Space Control Squadron:
*Socorro, New Mexico
Socorro (, ''Help:Pronunciation respelling key, sə-KOR-oh'') is a city in Socorro County, New Mexico, Socorro County in the U.S. state of New Mexico. It is in the Middle Rio Grande Valley AVA, Rio Grande Valley at an elevation of . At the 2020 ...
*AMOS
Amos or AMOS may refer to:
Arts and entertainment
* ''Amos'' (album), an album by Michael Ray
* Amos (band), an American Christian rock band
* ''Amos'' (film), a 1985 American made-for-television drama film
* Amos (guitar), a 1958 Gibson Fl ...
, Maui, Hawaii
Maui (; Hawaiian language, Hawaiian: ) is the second largest island in the Hawaiian archipelago, at 727.2 square miles (1,883 km2). It is the List of islands of the United States by area, 17th-largest in the United States. Maui is one of ...
*Diego Garcia
Diego Garcia is the largest island of the Chagos Archipelago. It has been used as a joint UK–U.S. military base since the 1970s, following the expulsion of the Chagossians by the UK government. The Chagos Islands are set to become a former B ...
, British Indian Ocean Territory
The British Indian Ocean Territory (BIOT) is an British Overseas Territories, Overseas Territory of the United Kingdom situated in the Indian Ocean, halfway between Tanzania and Indonesia. The territory comprises the seven atolls of the Chago ...
.
A site at Choe Jong San, South Korea
South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...
was closed in 1993 due to nearby smog from the town, weather and cost concerns. Originally, the fifth GEODSS was planned to be operated from a site in Portugal
Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
, but this was never built.
Moron Optical Space Surveillance (MOSS), a transportable telescope that contributed to the GEODSS system was operational at Morón Air Base, Spain () from 1997 to 2012.
GEODSS tracks objects in deep space, or from about out to beyond geosynchronous
A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital ...
altitudes. GEODSS requires nighttime and clear weather tracking because of the inherent limitations of an optical system. Each site has three telescopes. The telescopes have a aperture and a two-degree field of view. The telescopes are able to "see" objects 10,000 times dimmer than the human eye can detect. This sensitivity, and sky background during daytime that masks satellites' reflected light, dictates that the system operate at night. As with any ground-based optical system, cloud cover and local weather conditions directly influence its effectiveness. GEODSS system can track objects as small as a basketball more than in space or a chair at , and is a vital part of USSPACECOM's Space Surveillance Network. Each GEODSS site tracks approximately 3,000 objects per night out of 9,900 objects that are regularly tracked and accounted for. Objects crossing the International Space Station
The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...
(ISS) orbit within will cause the ISS to adjust their orbit to avoid collision. The oldest object tracked is Object #4 (Vanguard 1
Vanguard 1 (Harvard designation: 1958-Beta 2, COSPAR ID: 1958-002B ) is an American satellite that was the fourth artificial Earth-orbiting satellite to be successfully launched, following Sputnik 1
Sputnik 1 (, , ''Satellite 1''), ...
), launched in 1958.
Space Based Visible (SBV) Sensor
The SSN included one spaceborne sensor, the Space-Based Visible (SBV) sensor, carried into orbit aboard the Midcourse Space Experiment (MSX
MSX is a standardized home computer architecture, announced by ASCII Corporation on June 16, 1983. It was initially conceived by Microsoft as a product for the Eastern sector, and jointly marketed by Kazuhiko Nishi, the director at ASCII Corpo ...
) satellite launched by the Ballistic Missile Defense Organization
The Ballistic Missile Defense Organization (BMDO) was an agency of the United States Department of Defense that began on 20 May 1974 with the responsibility for all U.S. ballistic missile defense efforts. It was renamed the Missile Defense Agenc ...
in 1996. It was retired from service on June 2, 2008.
The Space Based Space Surveillance
The Space Based Space Surveillance (SBSS) system is a planned United States Space Force constellation of satellites and supporting ground infrastructure that will improve the ability of the United States Department of Defense (DoD) to detect and ...
( SBSS) pathfinder satellite now performs the mission previously handled by the MSX SBV.
The Canadian military satellite Sapphire
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name ''sapphire ...
, launched in 2013, also contributes data to the SSN.
Civil services
The USSPACECOM is primarily interested in the active satellites, but also tracks space debris
Space debris (also known as space junk, space pollution, space waste, space trash, space garbage, or cosmic debris) are defunct human-made objects in spaceprincipally in Earth orbitwhich no longer serve a useful function. These include dere ...
. As the number of space debris and the value of satellites in space grew, it has become important to protect civil economic activity and help satellite operators avoid collisions with debris. In 2010, USSTRATCOM was given authority to provide space situational awareness services to commercial and foreign actors. As of 2019, the following services are provided: positional data of all tracked objects, conjunction assessment, disposal/end-of-life support, and more through the space-track.org website.
See also
* Air Force Space Surveillance System
The AN/FPS-133 Air Force Space Surveillance System, colloquially known as the Space Fence, was a U.S. government multistatic radar system built to detect orbital objects passing over America. It is a component of the U.S. space surveillance ...
* Air Force Maui Optical and Supercomputing observatory
The Maui Space Surveillance Complex (MSSC) is a U.S. Space Force operating location for the 15th Space Surveillance Squadron and the Air Force Research Laboratory (AFRL) at Haleakala Observatory on Maui, Hawaii, with a twofold mission (). Fir ...
* Space Situational Awareness Programme
The Space Safety Programme, formerly the Space Situational Awareness (SSA) programme, is the European Space Agency's (ESA) initiative to monitor hazards from space, determine their risk, make this data available to the appropriate authorities and w ...
, the European Space Agency
The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...
's near-Earth object
A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit a ...
and space debris tracking programme
* Kessler syndrome
The Kessler syndrome, also known as the Kessler effect, collisional cascading, or ablation cascade, is a scenario proposed by NASA scientists Donald J. Kessler and Burton G. Cour-Palais in 1978. It describes a situation in which the density of o ...
* Satellite watching
Satellite watching or satellite spotting is a hobby which consists of the observation and tracking of artificial satellites that are orbiting Earth. People with this hobby are variously called satellite watchers, trackers, spotters, observers, ...
* Space debris
Space debris (also known as space junk, space pollution, space waste, space trash, space garbage, or cosmic debris) are defunct human-made objects in spaceprincipally in Earth orbitwhich no longer serve a useful function. These include dere ...
* Russia :
** Krona space object recognition station
Krona space object recognition station () is a Russian military complex which is used to identify objects (artificial satellites) in outer space using telescopes and radar.
Space surveillance base
It is part of the Centre for Outer Space Monito ...
and Krona-N, Russian telescope- and radar-based space surveillance facilities
** Okno
Okno ( meaning window) is a Russian space surveillance station located in Nurak in Tajikistan. It is run by the Russian Space Forces and is part of the Centre for Outer Space Monitoring. It is located above sea level in the Sanglok mountains, ...
and Okno-S, Russian telescope-based space surveillance facilities
** Main Space Intelligence Centre, the headquarters of the Russian military's space surveillance network, SKKP
References
External links
The Space-Track website
U.S. Strategic Command Space Surveillance
information on some of the latest events in orbital debris research.
*
A GEODSS Sourcebook
{{USAF system codes
Equipment of the United States Space Force
Programs of the United States Space Force
1957 establishments in the United States
Space program of the United States
Radar networks