SARSAT System Minnesota Wing Air Branch Director Course
COSPASS-SARSAT History • Initially developed under a MOU between the former USSR, USA, Canada and France in 1979. • Operational use started in 1982 with a crash of a light aircraft in Canada in which three people were rescued. • After some a test and evaluation phase, the system became fully operational in 1985. • COSPASS-SARSAT has been instrumental in the rescue of over 24,000 lives worldwide.
What is it? • A network of satellites used to detect emergency beacons used by persons in distress. • Contains both Low Earth Orbit Satellites (LEOSAR) and Geostationary Satellites (GEOSAR) • Monitors only 406 MHz beacons. • Monitoring of 121.5 MHz beacons ceased on 1 February 2009.
Two types of Satellites: • GEOSAR: Receives beacon identification almost instantaneously. Location information available if encoded in beacon message. No coverage near Earth’s poles. • LEOSAR: Used to provide beacon identification and location information. Global coverage, but not instantaneous.
How are beacons detected? • GEOSAR: • Receives 406 MHz Data burst transmission which contains a beacon identification number. • Instantaneous activation of the SAR System is possible. • If equipped, the beacon may also transmit it’s lat/long as part of the data burst. • If so, instantaneous location is possible. • If not, must wait for LEOSAR satellites must determine the location.
How are beacons detected? • LEOSAR: Uses a Doppler shift to detect beacon locations. • Takes a minimum of two passes to solve ambiguity and create what is called a “Merge”. • With 406 MHz beacons, accuracy is within 5 nm. • Satellite is in range on average, once every 45 minutes.
406 Beacons • Owners are required to register the new beacons. This information is kept in a database for retrieval if their beacon is activated. • Many false alarms are solved with a phone call to the owner asking them to turn their beacon off. • Transmit a very low power 121.5 signal for rescue teams to transmit.
Two equidistant candidate position solutions – these are called “elementals” Doppler Shift Position Solution • Doppler shift on 121.5 MHz provides two candidate positions • A second satellite pass is needed to determine which is the correct one Satellite Ground Track Satellite location at Doppler zero shift Perpendicular at Doppler zero shift
Doppler Shift Position Solution • Doppler shift on 121.5 MHz provides two candidate positions • A second satellite pass is needed to determine which is the correct one 2nd Satellite location at Doppler zero shift Position that agrees with 1st satellite – this is called a “merge”
How do we get called? • Emergency Beacon Signal is received by Satellite • Transmitted to Local User Terminal • Data received by Mission Control Center • Sent to Rescue Coordination Center (RCC) • Air Force Rescue (AFRCC) will investigate if they have owner information or can work with local airports to resolve. • If unable to resolve quickly, AFRCC calls CAP Duty officer and opens mission. • Duty officer alerts units.
What about 121.5?? • AFRCC is still issuing missions for 121.5 MHz beacons even without SARSAT data. • Airborne reports are the only method of detecting the beacons. • Airborne reports are far less accurate than SARSAT hits. • Depending on the altitude of the reports, the search area could be hundreds of miles in diameter.
Old Beacons vs. New • Actual Distress Rate: • 121.5: 2% or 1 in 50 is genuine • 406: 8% or 1 in 12 is genuine • Comparison of 121.5 and 406 MHz beacons:
What information to expect? • 121.5 MHz Beacons: • Airborne Reports • Reports from Airport FBOs if AFRCC called them. • 406 MHz Beacons: • Tail number (if in an aircraft) • Owner Information (if registered) • Latest SARSAT Merge • GPS coordinates of beacon if it is equipped with a GPS unit.
References • COSPAS-SARSAT Website • http://www.cospas-sarsat.org/