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The KH-11 was a reconnaissance satellite.
The KH-11, also referenced by the codenames Crystal and Kennan, also commonly known as "Big Bird", was a type of Reconnaissance satellite launched by the American National Reconnaissance Office from December 1976 to October 2005 and used until present. Manufactured by Lockheed, the KH-11 was the first American spy satellite to utilize electro-optical digital imaging, and create a real-time optical observation capability. It is believed to resemble the Hubble Space Telescope in size and shape, as the satellites were shipped in similar containers. Using a powerful 2.3-meter mirror, the theoretical ground resolution with no atmospheric degradation and 50% MTF would be roughly 0.15 metres (6 inches). Operational resolution would be worse due to effects of the atmosphere. Different versions of the KH-11 vary in mass from 13,000 to 13,500 kilograms. Length is believed to be 19.5 meters, and diameter is 3 meters or less. Data was transmitted through the United States military's Satellite Data System relay network.
The KH-11 replaced the KH-9 film return satellite, among others, the last of which was lost in a liftoff explosion in 1986. (Ref. 5)
The first KH-11 image was sent to an NRO facility at Fort Belvoir on January 20, 1977.
The last advanced KH-11 was launched on Oct. 19 2005 from Vandenburg AFB on the last Titan IV launch vehicle, into a 275 km by 1020 km orbit. Reported costs for the mission were $411 million for the launcher and $1 billion for the payload.
KH-11s generally operated for about three years, although it is believed that at least one was operational for 11 years. It is believed that the KH-11 began to be replaced by the KH-12 around 1990. Many observers believe that the KH-12 is really just an incremental improvement over the KH-11, so some still call later satellites KH-11s. The "Improved Crystal" nickname that the KH-12 has also comes from the idea that it is just incrementally better. The main difference is that the KH-12 might include the ability for "live" viewing of imagery. As of the last launch, four advanced KH-11's were thought to be in orbit along with 3 other types.
The KH-11/12 series are planned to be replaced by the Future Imagery Architecture digital imaging spacecraft from Lockheed Martin.
The KH is a military acronym for "Keyhole", a reference to "looking through a keyhole at someone".
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