The Search and Rescue Process
1. Distressed mariner/outdoor
adventurer/pilot activates beacon (EPIRB, PLB,
2. Beacon transmits a 406 MHz emergency message containing
your Unique Identifier Number (UIN) to the LEOSAR (polar orbiting)
and GEOSAR* (geostationary) satellite systems.
3. The satellites relay the 406 MHz emergency message to a
ground station called the Local User Terminal (LUT). The LUT
calculates the location of the signal by measuring the Doppler
shift caused by the relative movement between the satellite and the
beacon and forwards the location to the Mission Control Center
4. The MCC continues to receive information from
additional satellite passes and further refines the beacon position
(2.3 nm search radius). An alert message is generated that is
combined with the registration information from the
database and is forwarded to the appropriate Rescue Coordination
5. The RCC makes contact with the persons listed in the
database to verify the existence of an emergency and gathers
additional information about the beacon users. The RCC will
dispatch the closest, capable Search and Rescue (SAR) forces.
6. Local SAR forces launch a rescue mission and use the
121.5 MHz homing signal to pinpoint the beacon.
* On average, worldwide, this notification (steps 2 through 5)
take up to one hour for non-GPS beacons. For self-locating
beacons that provide GPS position data in their first
transmissions, the search radius is reduced to .05 nm (100 m) and
the notification can take as little as three minutes. (Data
provided by Cospas-Sarsat.)
Orbiting high overhead every minute of
the day is a worldwide network of polar-orbiting and geostationary
satellites. Together with Russia's Cospas spacecraft, they make up
the high-tech international Search and Rescue Satellite-Aided
Tracking System known as Cospas-Sarsat.
Cospas-Sarsat has been credited with
nearly 30,000 rescues worldwide. The system relies on signals
received on the 406 MHz frequency to pinpoint position and speed
rescuers to the scene of an emergency on land or at sea.
In fact, the more reliable, digital
406 MHz frequency has become the de facto internationally
recognized distress frequency. Using the 406 MHz frequency, modern
signaling devices can quickly beam GPS LAT/LON coordinates to
orbiting satellites. This frequency also allows a position fix
through Doppler shift to acquire a location even when GPS
As of February 1, 2009, satellite
processing of distress signals from the older 121.5 and 243 MHz
emergency beacons was terminated worldwide due to unreliability and
false alarms. When a 406 MHz beacon signal is received, search and
rescue personnel can retrieve information from a registration
This includes the beacon owner's
contact information, emergency contact information and details
regarding the specific trip plan and any medical conditions of the
owner or members in the party. Having this information allows the
Coast Guard, or other rescue personnel, to respond appropriately.
NOAA, along with the U.S. Coast Guard, is strongly advising all
mariners, aviators and individuals using 121.5/243 MHz emergency
beacons to make the switch to 406 MHz in order to take full
advantage of the Sarsat system.
Cospas-Sarsat is maintained and
operated by governments all over the world, thus there is no
subscription fee required for owning a 406 MHz EPIRB,
or Personal Locator Beacon.
Tags: Cospas Sarsat, 406 MHz Rescue, Search and Rescue Process,
Coast Guard Rescue, How a rescue works, Anatomy of a rescue, EPIRB,
Emergency Position Indicating Radio Beacon, Personal Locator
Beacon, PLB, Emergency Locator Transmitter, ELT
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