Incidents of beacon failure due to damage, as well as false alarms, employ a difficult and dangerous visual search method for locating a person in distress. Goddard has been investigating non-traditional methods to search for victims. Some of these techniques include: the incorporation 406 MHz repeaters into the Cospas-Sarsat system, and the development of a new class of beacons called "self-locating beacons."
The benefits of adding 406 MHz repeaters on U.S. geostationary satellites include:
 The satellite footprints cover a tremendous area of the Earth's surface
Beacon transmissions are received nearly instantaneously, significantly decreasing rescue response time
New self-locating beacons (see details below) also provide instant precise location
The GEO satellites provide redundancy for alert detection
Data from the GEO satellites allow improved Doppler location processing
GEO satellites have the potential to provide tracking.
"Self-locating beacons" are coupled to internal or external Global Positioning System (GPS) receivers, or other navigation receivers and transmit coded location information in the emergency message. External GPS receivers are coupled to the beacon via a serial interface. They function through both the LEO and GEO satellites and can also be located by conventional Doppler processing on the ground. When the geosynchronous satellites in the Cospas-Sarsat system receive the self-locating beacons, they can be located within minutes to the accuracy of the navigation receiver (presently 100 meters in the case of GPS). The self-location feature improves system reliability by providing redundancy.
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GPS Emergency Position Indicating Radio Beacons (EPIRB) |
GPS Emergency Locator
Transmitters (ELT) |
NASA Goddard was a major participant in the development of specifications, formats, transmission protocols, and rules for the use of self-locating beacons worldwide. Goddard developed the prototype self-locating EPIRBs, ELTs, and PLBs by modifying existing designs. The EPIRB and ELT modification work was performed by the Naval Research Laboratory.
The state-of-the-art miniature Personal Locator Beacon (PLB) was developed by NASA Small Business Innovation Research (SBIR) contracts funded by NASA and DOD. It is one of the smallest PLBs in the world, and can function through both the LEO and GEO satellites. The RF circuitry utilizes state-of-the-art GaAs technology which allows very high efficiency. Transmitter power efficiency on the order of 75% is obtainable as compared to 40% for conventional Radio Frequency (RF) technology. NASA Goddard supported the first experimental PLB program in the United States on the North Slope in Alaska. This highly successful program has saved over 75 lives to date since its inception in 1993. The Federal Communications Commission (FCC) approved the use of PLBs nationwide beginning on 1 July 2003.
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