SARSAT System

Minnesota WingAir 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.

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 location at Doppler zero shift

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

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.

http://www.sarsat.noaa.gov/New_C-S_System_Overview.jpg

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/

Questions?