August 1, 2011:
Two years ago, the United States put into orbit a pair of experimental STSS (Space Tracking and Surveillance System) satellites. These have better heat sensors and are there to provide earlier warning of ballistic missile launches, so that anti-missiles can hit ballistic missiles earlier, and with a higher probability of destroying them. STSS can also track other satellites, making it easier to destroy enemy satellites in wartime. STSS recently demonstrated an ability to detect short range, air-launched missiles.
STSS is another component of the BMEWS (ballistic missile early warning system). The half century old system uses radars and satellites to monitor the planet for ballistic missile launches (specifically ICBMs, but any large missile launch is detected.) If STSS passes more tests, it will become part of a new generation of BMEWS satellites.
Early on, BMEWS consisted of long range radars that could spot warheads coming over the North Pole (from Russia). When SSBNs (ballistic missile carrying nuclear subs) entered the Russian arsenal in the 1970s, BMEWS was augmented by satellites equipped with heat sensors that could detect the enormous amount of heat generated by a ballistic missile launch (or any large explosion, like an above-ground nuclear weapons test). These satellites cover the entire planet, while the radars only cover part of the Middle East. In all, 23 of these DSP (Defense Support Program) satellites have been launched (the latest four years ago). The 2.3 ton DSP birds are being replaced by SBIRS (Space-Based Infrared System), a network of four stationary orbit (like DSP) and 24 low orbit, heat sensing (infrared) satellites that will provide more detail than the DSP birds. SBIRS should be fully operational in another few years.
The United States has agreed to provide Israel with access to its BMEWS. Twice before, in 1991 and 2003, the U.S. allowed Israel to plug into BMEWS (to get warning of Iraqi missile launches). This time around, BMEWS will give Israel warning about any Iranian ballistic missiles headed west.