The US SARSAT geosynchronous experiment: ground processor description and test results

The concept of geosynchronous processing for satellite-aided search and rescue has existed since the inception of what is now the COSPAS/SARSAT program. As an augmentation of the operational low-Earth orbiting COSPAS/SARSAT system, geosynchronous processing of 406 MHz beacons promises increased probability of survival and reduced economic losses. This can be achieved since the variable of low-Earth orbiting satellite pass times is removed from the alert time-a geosynchronous satellite views nearly a hemisphere constantly. Geosynchronous processing therefore provides near-instantaneous (within 15 minutes) alerts, giving search-and-rescue forces valuable time to plan and implement a successful save operation. Although geosynchronous processing does not provide location estimates via Doppler processing (as in the COSPAS/SARSAT system), the capability for encoding of vessel location in some beacon protocols will allow not only near-instantaneous alerting but location as well. To investigate the feasibility of this approach, NASA initiated the geosynchronous experiment to develop a ground station and signal processor. This experiment has been pursued in cooperation with the CNES and DOC, each of whom are also developing ground stations and signal processors