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Introduction
Space surveillance provides information on what is orbiting Earth. 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.The smallest object that can be tracked is 4 inches (10 cm)in diameter. In addition, messages are sent to tactical commanders to warn them when they can be observed by a potential adversary's space systems.Surveillance is not a new idea, but it is only during the latter half of the twentieth century that the techniques and technologies have dramatically improved due to the huge advancements made in the Information Technology Industry. Surveillance was greatly used during the Cold War when Russian's and American's used spy satellites to spy on each others countries, most notably the Corona Spy Satellite launched by the USA. Bugging devices have been around for many years with the simplest being acoustic devices which work by directly intercepting communication with the naked ear, not considered as electronic, but techniques have now improved.As the twenty first century approaches and with the rapid increase in the use of the Internet, new types of surveillance methods are being developed namely data surveillance known as data veillance. All these surveillance technologies are examined in this document Satellites literally provide their owners an eye in the sky and when used for surveillance purposes are more commonly referred to as spy satellites. One major class of spy satellite are Imagery Intelligence Satellites (IMINT).Imagery Intelligence Satellites orbit at several hundred kilometers and use film and electronic cameras or radars to produce high resolution images of objects on the ground at ranges of up to one thousand kilometers.A certain type of IMINT satellite known as 'Keyhole Class' satellite performs area surveillance. This type of satellite returns images to Earth via an electronic link. The most advanced of these satellites have a resolution of around 10 - 15 cm which means they can distinguish an object that small, but no smaller. As an example, this type of satellite is not capable of reading license plates of vehicles but they can tell if a vehicle has one, and they cannot provide real-time images however other 'assets' such as can.A space based imaging radar can see through clouds and can potentially provide images with a resolution that approaches that of photographic reconnaissance satellites. A project to develop such a satellite by NASA is code named Lacrosse, first launched in 1988.
Space Surveillance Network
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
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
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.
Space Object
Identification (SOI).
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.
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.
The Baker Nunn 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 to22,300 miles (geostationary) and somewhat beyond. The position a space object in the photo is determined by analyzing the star background. Baker Nunn cameras are in operation in San Vito, Italy and in Saint Margarets, Newfoundland (operated by Canada). Many other Baker Nunn cameras have been replaced by GEODSS.Ground Based Electro-Optical Deep Space Surveillance System (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 Baker Nunn 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 Baker Nunn sites.
Maui Optical Tracking and Identification Facility (MOTIF)
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.
Navy Space Surveillance (NAVSPASUR) System.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 objects 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
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
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.
AN/FSP-108, CPBRA DANE
COBRA DANE is the project name for a single faced 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 L band 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
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.
Antigua
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 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
The Advanced Research Project Agency (ARPA) Long Range Tracking and Identification Radar (ALTAIR) and the ARPA Lincoln C Band 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, ALTAIR alone can track one third of the objects in the geosynchronous belt.
Saipan Space Surveillance Station
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.