7-54 - Space Surveillance Overview
a. Space surveillance provides information on what is orbiting Earth. This information includes each object's orbital parameters, size and shape, and other data useful for determining its purpose. Active and inactive satellites, along with space debris such as boosters, shrouds, and other objects are tracked. The smallest object that can be tracked is about 4 inches (10 cm) in diameter. Space surveillance provides essential information to the operators of space systems, helps to determine the capabilities of potential adversaries, predicts the orbits of objects in space to include warning of potential collisions, provides warning of an attack on a U.S. space system, and predicts space object reentry impact points. In addition, messages are sent to tactical commanders to warn them when they can be observed by a potential adversary's space systems.
b. The U.S. Space Surveillance Network (SSN) is a collection of radar and optical sensors used to detect, track and identify objects in space. Although referred to as a network, the Space Surveillance Network was not originally planned as such. As various sensors became available, their particular capabilities were used to contribute to the space surveillance mission. The Space Surveillance Network cannot continuously track all satellites, therefore the Space Surveillance Center prepares a prioritized list of satellites to track. Generally, satellites with high interest missions or unstable orbits (objects about to deorbit) will have higher priority data collection requirements than other satellites.
Categories of Sensors c. The Space Surveillance Network is organized into three categories of sensors:
Dedicated Government owned sensors with a primary mission of space surveillance.
Collateral Government owned sensors with a primary mission other than space surveillance.
Contributing Owned and operated by other agencies but which provide surveillance data when
not performing their primary mission.
Space Surveillance Center d. The Space Surveillance Center (SSC), operated by the U.S. Space Command, is located in Cheyenne Mountain, Colorado. The SSC maintains a database on all identifiable objects in Earth orbit. The database includes about 10,000 objects. The SSC provides a variety of routine and special reports to operational military commands, NASA, NOAA, other organizations and the scientific community.
7-54 - Space Surveillance Overview, cont'd
Tracking of Space Objects e. Tracking space objects is an iterative process. The SSC starts the process by developing a predicted element set (orbital parameters) of the object's orbit. The Space Surveillance Center sends the element set to selected sensors in the SSN. The sensors search the skies in the predicted location, at the predicted time. If the prediction is close, the sensor will detect and track the object. The tracking data are sent back to SSC for processing and analysis. The SSC uses this information to compute a new element set, or prediction. This prediction is then sent back out to the sensors, and the cycle is repeated.
Space Object Identification (SOI) f. The Space Surveillance Network sensors also collect information which is used to perform Space Object Identification (SOI). SOI is the analysis of data from sensors to determine a satellite's size, shape, motion, orientation and operational status. SOI is a technical discipline that is similar to imagery interpretation.
7-55 Dedicated Sensors: Optical
Introduction a. Optical sensors are basically telescopes, gathering light reflected off an object in space. Like all telescopes, they have limitations; for example, they cannot track objects in Earth's shadow unless they are emitting light. Cloud cover, fog, atmospheric pollution, light glow from cities or a full moon degrade or prevent observations. The size of the object to be tracked and its distance from Earth are also limiting factors.
Baker Nunn Camera b. The BakerNunn camera is a large telescope with a camera attached. Imagery is recorded on film. Two to four hours are required for on site film processing and image analysis after which data is transmitted to the Space Surveillance Center. The system can image satellites ranging in altitude from 3,000 miles to 22,300 miles (geostationary) and somewhat beyond. The position a space object in the photo is determined by analyzing the star background. BakerNunn cameras are in operation in San Vito, Italy and in Saint Margarets, Newfoundland (operated by Canada). Many other BakerNunn cameras have been replaced by GEODSS.
Ground Based Electro-Optical Deep Space Surveillance System (GEODSS) c. GEODSS is an electronically enhanced telescope that uses low light level television cameras and a computer instead of film. Sensor data are stored on magnetic media for analysis locally or the data are transmitted in near real time to the Space Surveillance Center for analysis, if required. The GEODSS sensors are more sensitive than the BakerNunn cameras, therefore they can detect, image and track smaller and dimmer objects. The system can image objects in space with an altitude of more than 22,000 miles. The GEODSS sensors provide vary accurate data which make them excellent for providing data to maintain the space object catalog. The sensors only operate at night. Weather conditions and a full moon restrict viewing opportunities. Each GEODSS site has three telescopes, each facing a different section of the sky. There are four GEODSS sites:
Cicero, New Mexico
Choe Jong San (near Taegu), Korea
Maui, Hawaii
Diego Garcia, Indian Ocean
A fifth GEODSS site in Portugal has been proposed. It would replace the two remaining BakerNunn sites.
Maui Optical Tracking and Identification Facility (MOTIF) d. MOTIF is an optical sensor similar to the GEODSS with an added Long Wave Infrared (LWIR) detection system. It performs near Earth and deep space surveillance and Space Object Identification. The range is similar to that of the GEODSS. The sensor is only operated at night. Clouds, high winds, high humidity and a full moon restrict viewing opportunities. MOTIF is collocated with the GEODSS site in Maui, Hawaii.
7-56 Dedicated Sensors: Radar
Navy Space Surveillance (NAVSPASUR) System a. The NAVSPASUR system consists of three transmitters and six receivers located along the 33d parallel in the U.S. The transmitters emit a vertical continuous beam which forms an electronic fence. When an object passes through one of the transmitter's waves in space and two or more geographically separated receivers detect the reflected energy, the object's location can be determined by triangulation derived by interferometric techniques. This is essentially the same process that bistatic radars use. Once the object's location and general direction of movement are determined, NAVSPASUR operators notify the Space Surveillance Center, which can then notify a tracking radar to make more precise determinations of the object's characteristics. The range of this fence is 5,000 miles in length and can detect objects up to 15,000 miles out in space. The space object in orbit must have an inclination of greater than 33 degrees in order to pass through the electronic fence. It does not track, it only detects. More than one million detections are made every month.
Transmitters b. Transmitters are located at Gila River, Arizona; Lake Kickapoo, Texas; and Jordan Lake, Alabama. Receivers are located at Fort Stewart, Georgia; Hawkinsville, Georgia; Silver Lake, Mississippi; Red River, Arkansas; Elephant Butte, New Mexico; and San Diego, California. NAVSPASUR headquarters is at Dahlgren, Virginia. The headquarters is also the Alternate Space Defense Operations Center and the Alternate Space Surveillance Center.
AN/FPS-85, Phased Array Radar c. The AN/FPS85 Phased Array Radar is located at Eglin AFB, Florida. The radar is housed in a wedge shaped building that is 318 feet long. The transmitter side has 5,928 elements and is 126 feet tall. The receiver side has 19,500 elements and is 192 feet tall. The radar was originally built to detect Sea Launched Ballistic Missiles (SLBM). It became a dedicated space sensor in 1988, when the PAVE PAWS radar at Warner Robins AFB, Georgia became operational. The radar has the capability to track near Earth and deep space objects simultaneously. Approximately 95% of objects in low Earth orbit pass through this radar's coverage.
7-56 Dedicated Sensors: Radar, cont'd
Saipan Space Surveillance Station d. The Saipan Space Surveillance Station, on the Pacific island of Saipan, is well suited to monitor launches from China and the central Asian land mass . It transmits a single radar beam toward its target in space. From the reflected energy the systems is able to calculate the size, orientation, altitude, speed and direction of movement. The system is not suitable for searching the sky for satellites. The radar must first be queued so that it is pointed in the correct position. The radar can track an object in space with high precision, but it can only track one object at a time.
Deep Space Tracking System e. The Deep Space Tracking System uses sensitive, highly accurate, 60foot dish antennas to detect and track Sband radio signals transmitted by radio beacons on most satellites. There are DSTS receivers located at Griffiss Air Force Base, New York; RAF Feltwell, Great Britain; and Misawa Air Base, Japan. These sites are expected to become operational in 1993 and 1994. The signals transmitted by most satellites are not significantly affected by weather and can operate during the day and at night. The system is capable of tracking many satellites in a short amount of time. This will allow the other optical and radar sensors to detect and track other unidentified objects in space. Since they rely on transmissions from the satellites, they cannot detect or track space debris or totally inactive satellites.
7-57 Collateral Sensors
Ballistic Missile Early Warning System (BMEWS) a. The primary mission of BMEWS is to provide early warning and attack assessment of missile attacks launched against CONUS and southern Canada from the Asian land mass that pass over or near the North Pole. The system also serves to provide SLBM and ICBM warning/attack assessment for the United Kingdom and Europe. The radars are capable of tracking multiple space objects, however the capability is limited to relatively large objects in low Earth orbit.
BMEWS Sites b. BMEWS sites are located at:
Thule, Greenland (Site 1) A phased array radar, installed in 1987, provides 240 degree coverage
against large objects such as ICBMs or SLBMs.
Clear AFB, Alaska (Site 2) This site is equipped with 1961 vintage radars. They have proven
to be very reliable, with a historical 99% availability rate.
Royal Air Force Station, Flyingdales, Great Britain (Site 3) The site was initially built in 1964.
It has three phased array radars which provide 360 degree coverage for warning/attack
assessment of ICBM and SLBM attacks.
PAVE PAWS c. PAVE PAWS is a system of radar complexes with a primary mission to provide warning/attack assessment of SLBM attack against CONUS and southern Canada. Each site operates a dualfaced phased array radar. The two northern sites (Cape Cod and Beale) can also provide warning/attack assessment of an ICBM attack from the Asian land mass. Each site can also provide satellite tracking data for space surveillance. The sensitivity of the radar limits detection and tracking to low Earth orbits of relatively large objects. Sites are located at:
Cape Cod AFS, Massachusetts
Beale AFB, California
Robins AFB, Georgia
Eldorado AFS, Texas
Due to a reduced threat, the PAVE PAWS system does not operate at all times.
7-57 Collateral Sensors, cont'd
AN/FSP-108, CPBRA DANE d. COBRA DANE is the project name for a singlefaced phased array radar located at Shemya AFB, Alaska. Its primary mission is intelligence, with secondary emphasis being space surveillance. It can also perform warning/attack assessment for missile attacks. The radar operates in the Lband which provides better accuracy and sensitivity than Pave Paws. Due to its position, COBRA DANE provides important information on new foreign launches.
AN/FSP-79, Pirinclik, Turkey e. The AN/FSP79 radar, located at Pirinclik, Turkey, has the same general mission as COBRA DANE. This system has two detection radars and a tracking radar. Two objects can be tracked simultaneously. It is the only 24hour a day deep space sensor in the eastern hemisphere.
AN/FPQ-16, Perimeter Acquisition Radar Attack Characterization System (PARCS) f. PARCS is a leftover from the Safeguard AntiBallistic Missile system at Cavalier AFB, North Dakota. Following the deactivation of Safeguard, the Army transferred PARCS to the Air Force. The Air Force assigned the radar a primary mission of warning/attack assessment of SLBM and ICBM attack against CONUS and southern Canada. Its singlefaced phased array radar is pointed northward over the Hudson Bay. It can provide valuable surveillance, tracking, reporting, and Space Object Identification data for the Space Surveillance Network. In June 1992, the Air Force deactivated the site and placed it in extended storage.
7-58 Contributing Sensors
Millstone Hill Radar and Haystack Long Range Imaging Radar a. These two radars, commonly referred to as the Millstone/Haystack Complex, are located in Lexington, Massachusetts. They are owned and operated by Lincoln Laboratories of the Massachusetts Institute of Technology (MIT). Millstone is a deep space radar that contributes 80 hours per week to tracking for the Space Surveillance Center. Haystack is a deep space imaging radar that provides wideband Space Object Identification data to the Space Surveillance Center about once every six weeks. In addition to the scheduled use of Haystack, USSPACECOM has the option to call on it two additional times in a year.
Antigua b. A tracking radar is installed on Antigua, British West Indies off the coast of Venezuela. This radar is part of the Eastern Test Range which supports launches from the Eastern Space and Missile Center (Cape Kennedy and Cape Canaveral, Florida). The radar is very accurate, but has a limited search capability.
Ascension Island c. A tracking radar, similar to the one on Antigua, is installed on this island located off the coast of Africa near the Equator. It also is part of the Eastern Test Range.
ALTAIR and ALCOR d. The Advanced Research Project Agency (ARPA) LongRange Tracking and Identification Radar (ALTAIR) and the ARPA Lincoln CBand Observable Radar (ALCOR) are on the island of Kwajalein in the western Pacific. Operated by the Army, they are primarily used for ABM testing in support of the Western Space and Missile Center (WSMC). They support space surveillance missions when possible. ALCOR is a near Earth tracking radar, and is the only other radar besides Haystack that can provide wideband Space Object Identification. ALTAIR is a near earth and deep space tracking radar. Because of its nearness to the equator, ALTAIR alone can track onethird of the objects in the geosynchronous belt.
Kaena Point e. Kaena Point is a tracking radar located on Oahu, Hawaii. It is part of the Western Test Range and reports to the Western Space and Missile Center. When not being used for test support, it supports the Space Surveillance Center with very accurate satellite tracking data.
Advance Research Program Agency (ARPA) Maui Optical Station (AMOS) f. AMOS is a similar to the GEODSS type optical sensor except that it has a deformable mirror to compensate for atmospheric disturbance, thereby creating clearer, sharper imagery. Operation is limited to nighttime only. Clouds and bright lights further restrict viewing opportunities. It is collocated with the GEODSS and MOTIF sensors on Maui. Its primary mission is to support research and development. [RETURN]