Space Shuttle program March 25, 1979, and was first launched on April 12, 1981—the 20th anniversary of Yuri Gagarin's space flight—with a crew of two. "Challenger" (OV-099) was delivered to KSC in July 1982, "Discovery" (OV-103) in November 1983, "Atlantis" (OV-104) in April 1985 and "Endeavour" in May 1991. "Challenger" was originally built and used as a Structural Test Article (STA-099), but was converted to a complete orbiter when this was found to be less expensive than converting "Enterprise" from its Approach and Landing Test configuration into a spaceworthy vehicle. On April 24, 1990, "Discovery" carried the Hubble Space Telescope into space during
Space Surveillance Telescope Space Surveillance Telescope The Space Surveillance Telescope is a telescope for detecting and tracking orbital debris. It has a 3.5 meter (138″) aperture mirror and came online in 2011. Two noted design features include Mersenne-Schmidt type optics and a curved CCD. In 2010s the telescope, which was in New Mexico, United States, was transferred to United States Air Force Space Command and moved to Australia. The discovery and tracking of space debris is noted as a growing problem in the 21st century. One problem is that among the 20-30 thousand large objects in orbit that are tracked, and an estimated