1. Minnesota Wing Air Branch Director Course
SARSAT System
Minnesota Wing
Air Branch Director Course

2. 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.

3. 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 MHz beacons ceased on 1 February 2009.

4. 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.

5. 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.

6. 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.

7. 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 signal for rescue teams to transmit.

8. Doppler Shift Position Solution
Doppler shift on 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
Two equidistant candidate position solutions – these are called “elementals”
Perpendicular at
Doppler zero shift

9. Doppler Shift Position Solution
Doppler shift on 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”

10. 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.

12. What about 121.5??
AFRCC is still issuing missions for 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.

13. 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 and 406 MHz beacons:

14. 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.

15. References
COSPAS-SARSAT Website

16. Questions?