April 9, 2012: The first of four military reconnaissance satellites to be sent up in the next five months was launched from Vandenberg Air Force Base in California on April 3rd. The satellite was not identified, but the Delta 4 Medium+ 5,2 rocket used can put 7.9 tons into low orbit (where military recon satellites usually operate). The KH-11 photo satellites weigh over 12 tons, so this recent launch was apparently something else, like a radar or electronic intelligence collecting bird or an early warning (of missile launches) satellite. These smaller spy satellites are rarely discussed openly.
For example, last year, without any announcement, an American Lacrosse radar satellite was destroyed when ground controllers ordered it to leave orbit and plunge towards the earth (where it burned up during reentry). This particular Lacrosse bird served for two decades, more than twice as long as it was expected to last. This event was only known because of the many amateur astronomers who track satellites and post their findings on the Internet.
There are now at least three Lacrosse satellites in orbit, the oldest of them launched in 1997, while the most recent went up in 2005. The first Lacrosse went up in 1988, and was brought down (deorbited/destroyed) in 1997. The Lacrosse birds fly a low orbit (about 700 kilometers up) to facilitate the use of their radar. Because of their large size and low orbit, they can often be seen, under the right light conditions, with the naked eye.
For decades the U.S. has usually had four KH-11s and four Lacrosse radar satellites in orbit, plus several smaller and more secret birds. Often, these satellites last longer than their design life of eight years (some have gone on for 10-15 years). Eventually they all wear out. The KH-11 and Lacrosse satellites weigh 14-16 tons, although there are supposed to be smaller, lighter radar satellite designs in the works.