Cospas-Sarsat is in the process of upgrading its satellite system by placing search-and-rescue receivers (i.e., repeaters or transponders) on new GPS satellites operated by the United States, navigation satellites of Russia (GLONASS) that began deployment last year, and European GALILEO navigation satellites that began launching 12 October 2012. Once qualified as operational, this system augmentation will dramatically improve both the speed and location-accuracy for detecting beacons.
Those satellites orbit the Earth at an altitude between 19,000 and 24,000 km, a range considered as medium-altitude Earth orbit. Hence this component of Cospas-Sarsat is known as the Medium-altitude Earth Orbit Search and Rescue system or MEOSAR. It will complement the existing LEOSAR and GEOSAR systems.
The current LEOSAR and GEOSAR systems contribute respective advantages to the detection and location of distress beacons that have been activated. The GEOSAR system constantly covers the entire Earth except for the high-latitude (e.g., polar) regions. While the GEOSAR system can receive beacons distress messages across most of the globe, it cannot locate the beacon unless the location is encoded in the beacon’s message from a local navigation receiver. The LEOSAR system can locate a beacon without the aid of a GPS or other navigation signal to the beacon, but the LEOSAR satellites have a view of only a small part of the Earth at any given time, so there may be a delay in receiving the distress signal over LEOSAR.
Once fully operational, the MEOSAR system will offer the advantages of both LEOSAR and GEOSAR systems without their current limitations by providing transmission of the distress message, and independent location of the beacon, with a near real-time worldwide coverage.
The MEOSAR system also will facilitate other planned enhancements for Cospas-Sarsat beacons, such as a return link transmission that will allow the beacon to provide to the user a confirmation that the distress message has been received.
The large number of MEOSAR satellites that will be in orbit when the system is fully operational will allow each distress message to be relayed at the same time by several satellites to several ground antennas, improving the likelihood of detection and the accuracy of the location determination.
The MEOSAR System Concept
