The COSPAS-SARSAT system
Operational use of the COSPAS-SARSAT system by SAR agencies started with the crash of a light aircraft in Canada on 10 September 1982, from which three people were rescued. Since then, the system has been instrumental in the rescue of over 35,000 lives in over 9600 incidents worldwide.
The basic COSPAS-SARSAT concept is illustrated on page 5.7. The system is composed of:
- distress beacons (ELTs, PLBs, EPIRBs)
- instruments on board geostationary earth orbit (GEO) and low-altitude earth orbit (LEO) satellites, which detect the signals transmitted by distress beacons
- Local Users Terminals (LUT) are ground receiver stations which receive and process the satellite downlink signal to generate distress alerts
- Mission Control Centres (MCC), which receive alerts produced by LUTs and forward them to Rescue Coordination Centres (RCC), Search and Rescue Points of Contact (SPOC) or other MCCs.
The COSPAS-SARSAT system includes two types of satellites:
- satellites in LEO which form the LEOSAR System
- satellites in GEO which form the GEOSAR System.
The future COSPAS-SARSAT system will include a number of a new type of satellite in medium-altitude earth orbit (MEO), which will form the MEOSAR System.
COSPAS-SARSAT has demonstrated that the GEOSAR and LEOSAR system capabilities are complementary. For example, the GEOSAR system can provide almost immediate alerting in the footprint of the GEOSAR satellite, whereas the LEOSAR system:
- provides coverage of the polar regions (which are beyond the coverage of GEO satellites)
- can calculate the location of distress events using doppler processing techniques
- is less susceptible to obstructions which may block a beacon signal in a given direction because the satellite is continuously moving with respect to the beacon.
RCC Australia’s usage of the COSPAS-SARSAT system
The COSPAS-SARSAT system only detects and locates distress beacons operating at 406 MHz.
Processing of 121.5 MHz and 243 MHz signals by COSPAS-SARSAT ceased on 1 February 2009.
Consequently, over-flying aircraft are the only means of detecting activated analogue beacons. In some areas within the Australian search and rescue region this could mean it would take days rather than hours before a 121.5 MHz beacon could be heard. In some circumstances, the 121.5 MHz beacon may not be detected at all. Not all aircraft ‘listen’ to the 121.5 MHz frequency and those that do are generally very high flyers. As a consequence, the search area resulting from these detections could be very large and it would take rescue authorities considerable time and resources to localise the distress signal. This would also apply to distress beacons activated directly under a high air-traffic density flight path.
Australian LUTs are controlled by the MCC at RCC-Australia in Canberra. There are three LUTs in the Australian region:
- Albany (WA)
- Bundaberg (QLD)
- Wellington (NZ).
Alerts from 406 MHz distress beacons can be received and processed by GEO satellites and passed to RCC Australia within minutes. If the beacon has GPS capability a very accurate position transmitted with the alert. Non-GPS beacons require detection by a polar earth orbit (POE) satellite before a position can be obtained.