United States Space Surveillance Network

The United States Space Surveillance Network (SSN) detects, tracks, catalogs and identifies artificial objects orbiting Earth, e.g. active/inactive satellites, spent rocket bodies, or fragmentation debris. The system is the responsibility of United States Space Command and operated by the United States Space Force and its functions are:

Predict when and where a decaying space object will re-enter the Earth's atmosphere;
Prevent a returning space object, which to radar looks like a missile, from triggering a false alarm 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;
Space Surveillance Telescope (SST)
MOSS - an Electro-Optical (E-O) surveillance system located at the Morón Air Base, Spain
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
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, Hawaii
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, Kwajalein Atoll
Ascension Range Radar, locate at the Eastern Spacelift Range
Ground-Based Radar Prototype (GBR-P), located Ronald Reagan Ballistic Missile Defense Test Site, Kwajalein Atoll

Auxiliary sensors

Solid State Phased Array Radar System (SSPARS) / AN/FPS-132 Upgraded Early Warning Radar (UEWR) system of system, deployed at multiple sites
AN/FPS-108 Cobra Dane
AN/FPQ-16 Perimeter Acquisition Radar Characterization System (PARCS)

Ground-based Electro-Optical Deep Space Surveillance

Ground-based Electro-Optical Deep Space Surveillance, or GEODSS, is an optical system that uses telescopes, low-light level TV cameras, and computers. It replaced an older system of six 20-inch (510 mm) Baker-Nunn cameras which used photographic film.

There are three operational GEODSS sites that report to the 20th Space Control Squadron:

Socorro, New Mexico 33°49′02″N 106°39′36″W / 33.8172°N 106.6599°W / 33.8172; -106.6599
AMOS, Maui, Hawaii 20°42′32″N 156°15′28″W / 20.7088°N 156.2578°W / 20.7088; -156.2578
Diego Garcia, British Indian Ocean Territory 7°24′42″S 72°27′08″E / 7.41173°S 72.45222°E / -7.41173; 72.45222.

A site at Choe Jong San, South Korea 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, but this was never built.

Moron Optical Space Surveillance (MOSS), a transportable 22-inch-aperture (560 mm) telescope that contributed to the GEODSS system was operational at Morón Air Base, Spain (37°10′12″N 5°36′32″W / 37.170°N 5.609°W / 37.170; -5.609) from 1997 to 2012.

GEODSS tracks objects in deep space, or from about 3,000 miles (4,800 km) out to beyond geosynchronous 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 40-inch (100 cm) 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 20,000 miles (32,000 km) in space or a chair at 35,000 miles (56,000 km), 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 (ISS) orbit within 20 miles (32 km) will cause the ISS to adjust their orbit to avoid collision. The oldest object tracked is Object #4 (Vanguard 1), launched in 1958.^{[citation needed]}

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) satellite launched by the Ballistic Missile Defense Organization in 1996. It was retired from service on June 2, 2008.

The Space Based Space Surveillance (SBSS) pathfinder satellite now performs the mission previously handled by the MSX SBV.

The Canadian military satellite 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. 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.

Ground-based Electro-Optical Deep Space Surveillance

Space Based Visible (SBV) Sensor

Civil services

See also