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carriers followed by a digital message format that provides identification data. The 406 MHz system uses
Satellite-borne equipment to measure and store the Doppler-shifted frequency along with the beacons
digital data message and time of measurement. This information is transmitted in real time to an earth
station called the Local User Terminal (LUT), which may be within the view of the satellite, as well as being
stored for later transmission to other LUTs.
The LUT processes the Doppler-shifted signal from the LEOSAR and determines the location of the
beacon; then the LUT relays the position of the distress to a Mission Control Center (MCC) where the
distress alert and location information is immediately forwarded to an appropriate Rescue Coordination
Center (RCC). The RCC dispatches Search and Rescue (SAR) forces.
The addition of the GEOSAR Satellite system greatly improves the reaction time for a SAR event. This
satellite system has no Doppler capabilities at 406 MHz, but will relay the distress alert to any of the LUT
stations. When there is GPS data included in the distress message, SAR authorities instantly know your
location to within 110 yards. This speeds up the reaction time by not having to wait for one of the LEOSAR
satellite to pass overhead. Because most of the search and rescue forces presently are not equipped to
home in on the 406 MHz Satellite beacons signal, homing must be accomplished at 121.5 MHz.
6.3
Global Positioning System (GPS)
The GPS system is a satellite group that enables a GPS receiver to determine its exact position to within
30m anywhere on Earth.
With a minimum of 24 GPS satellites orbiting the Earth at an altitude of
approximately 11,000 miles they provide users with accurate information on position, velocity, and time
anywhere in the world and in all weather conditions. The ThunderBird SSAS stores this data into its
distress transmission allowing search and rescue forces to narrow the search into a very small area and
thus minimize the resources required and dramatically increases the effectiveness of the overall operation.
FIGURE 8 - SATELLITE COVERAGE
FIGURE 9 - GEOSAR SATELLITE ORBITS
FIGURE 10 - GPS SATELLITE ORBITS
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Y1-03-0180 Rev. D
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