A number of weather and environmental satellites, such as the US NOAA and the Russian Cospas, carry extra circuitry that enables them to pick up emergency signals from downed aircraft and ships in distress. They automatically relay these signals to ground-sea-air rescue services, pinpointing the location of the stricken craft. This programme, known as Sarsat (satellite aided search and rescue), has been in operation since 1982, and has been responsible for saving several thousand lives.
