AMOS, Maui, Hawaii Diego Garcia, British Indian Ocean Territory . 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 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 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 or a chair at , and is a vital part of USSPACECOM's Space Surveillance Network. Distant Molniya orbiting satellites are often detected in elliptical orbits that surpass the Moon and back (245,000 miles out). Each GEODSS site tracks approximately 3,000 objects per night out of 9,900 object that are regularly tracked and accounted for. Objects crossing the International Space Station (ISS) orbit within will cause the ISS to adjust their orbit to avoid collision. The oldest object tracked is Object #4 (Vanguard 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) 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