Ground-based Electro-Optical Deep Space Surveillance (GEODSS), Diego Garcia

 military, satellite/space tracking station

There are three operational GEODSS sites that report to the 21st Operations Group: Socorro, New Mexico; Maui, Hawaii; and Diego Garcia, British Indian Ocean Territory. A site at Choe Jong San, South Korea was closed in 1993 due to weather and cost concerns. GEODSS is an optical system that uses telescopes, low-light level TV cameras, and computers. It replaced an older system of six 20 inch (half meter) Baker-Nunn cameras using photographic film.

GEODSS tracks objects in deep space, or from about 3,000 mi (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 (1.02 m) 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 (30,000 km) in space, and is a vital part of USSTRATCOM’s Space Surveillance Network.