is an imaging spy satellite
(spysat) orbited by the United States. There were/are several KH-11s. They are referred to as 'KeyHole' satellites; I'm not sure if the phoenetic preceded or followed the designation. These satellites operate at altitude
s of between 250 and 800 km
; from there they image designated ground targets, storing their images digitally
. The data is then dumped
to ground station
s for relaying to American intelligence
agencies for analysis. Funding for these appears to have come from a variety of sources, including the CIA
, the Air Force
, and the NRO
, among others.
A purported example of KH-11 imagery can be found on the web at:
...although it is likely that the actual capabilities of the satellite may be in fact even greater. The lifespan of such a satellite on orbit is between 2 and 3 years. The primary factor in this lifespan is the availability of maneuvering fuel, and one of the funding rationales for the Space Shuttle was as a resupply and repair transport for satellites such as these. The reasoning is clear when it is taken into account that the costs of building and launching a KH-11 may easily exceed one or two billion dollars, and needs for them may arise faster than the pipeline can supply them. In contrast, a shuttle mission costs on the close order of $400 million; if that mission can refuel and repair two KH-11s, it's a bargain.
The first such bird, KH-11-1, was launched from Vandenberg AFB in California USA in December, 1976. It deorbited in early January 1979. Its perigee was 246km; its apogee 531km. Its orbital inclination was 96.9 degrees, and its orbital period roughly 92 minutes. (source: The Satellite Encyclopedia).
Note that spy satellites are a diffferent type of launch and orbit than civilian-use satellites. In order to allow one satellite to cover as much of the planet as possible, these satellites are typically in a north-south orbit (96 degrees as mentioned above, with 90 degrees being perfectly polar), as opposed to an east-west orbit. This makes them difficult to contact from the ground as they are constantly moving overhead, but allows them to image anywhere on the planet with varying response times. In order to place them in these orbits, they require powerful boosters since they cannot use the rotational speed of the Earth to gain a jump start on orbital velocity. They are usually quite large and heavy besides.