One of the three remaining Russian satellites built to detect ICBM launches has failed. The failed satellite was an Oko-1 that was launched in 2012 and was supposed to last 5-7 years. Russia began launching the Oko-1 satellites in 1991 but only two of them have lasted more than five years. The Oko-1s are GTO (high stationary orbit) type satellites costing $45 million each and two are needed to provide worldwide coverage. The older satellites are in lower, non-stationary orbit and with only two of the pre-Oko-1 satellites left Russia can detect American ICBM launches for only about three hours a day. Russia is not completely blind as it is rebuilding its network of long range (over-the-horizon) radars. These provide less warning, and less time to decide what to do.
The U.S. has been able to maintain its Cold War ICBM early warning capability and is planning to expand it. For example, in 2009 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-missile 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 also 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 directions where missiles might come from. In all, 23 of these DSP (Defense Support Program) satellites have been launched (the latest in 2007). 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. So far seven of 37 SBIRS have been launched but completing this system depends on cost control and effectiveness being maintained. That has proved difficult to do.