SARSAT System

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SARSAT System

• Minnesota Wing
• Air Branch Director Course

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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.

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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.

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Two types of Satellites

• GEOSAR Receives beacon identification almost
  instantaneously. Location information available
  if encoded in beacon message. No coverage near
  Earths poles.
• LEOSAR Used to provide beacon identification and
  location information. Global coverage, but not
  instantaneous.

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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 its
  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.

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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.

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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.

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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
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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
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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.

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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.

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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

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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.

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References

• COSPAS-SARSAT Website
• http//www.cospas-sarsat.org/

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Questions?