Satellites Used
Receivers are auxiliary systems mounted on several types of satellites. This substantially reduces the program's cost.
The weather satellites that carry the SARSAT receivers are in "ball of yarn" orbits, inclined at 99 degrees. The longest period that all satellites can be out of line-of-sight of a beacon is about two hours.
The first satellite constellation was launched in the early 1970s by the Soviet Union, Canada, France and the USA.
Some geosynchronous satellites have beacon receivers. Since end of 2003 there are four such geostationary satellites (GEOSAR) that cover more than 80% of the surface of the earth. As with all geosynchronous satellites, they are located above the equator. The GEOSAR satellites do not cover the polar caps.
Since they see the Earth as a whole, they see the beacon immediately, but have no motion, and thus no doppler frequency shift to locate it. However, if the beacon transmits GPS data, the geosynchronous satellites give nearly instantaneous response.
Read more about this topic: Distress Radiobeacon
Famous quotes containing the word satellites:
“To the Japanese, Portugal and Russia are neutral enemies, England and America are belligerent enemies, and Germany and her satellites are friendly enemies. They draw very fine distinctions.”
—Jerome Cady, U.S. screenwriter, and Lewis Milestone. Peter Voroshevski (Howard Clinton?)