Acrartex TerraFix 406 GPS PLB User Manual download pdf (Page 13)

Y1-03-0174 Rev. E 12

7.2 Satellite Detection

7.2.1 The TerraFix™ 406 GPS transmits an encoded phase modulated radio signal to the satellite portion

of the COSPAS-SARSAT System. The system was developed and implemented by the COSPAS-

SARSAT Partners (Russian Federation, Canada, France and the United States).

7.2.2 COSPAS-SARSAT is an international system that uses Russian Federation and United States low

altitude, near-polar orbiting satellites (LEOSAR) that assist in detecting and locating activated

121.5/243 MHz PLBs and 406 MHz Satellite PLBs.

7.2.3 COSPAS and SARSAT satellites receive distress signals from satellite PLBs transmitting on the

frequency of 406 MHz. The COSPAS-SARSAT 406 MHz PLB signal consists of a transmission of

non-modulated 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 PLB 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.

7.2.4 The LUT processes the Doppler-shifted signal from the LEOSAR and determines the location of the

PLB; 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.

7.2.5 The COSPAS-SARSAT System includes 39 LEOSAR LUT stations, 9 GEOSAR LUT stations and

over 19 Mission Control Centers that provide real-time as well as global-mode coverage for the

Northern Hemisphere, while the Southern Hemisphere is presently served primarily by the global

mode. Additional LUTs and MCCs are planned for installation in the near future both in the northern

and southern hemispheres.

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.

7.2.6 Because most of the search and rescue forces presently are not equipped to home in on the 406 MHz

Satellite PLB signal, homing must be accomplished at 121.5 MHz.

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Acrartex TerraFix 406 GPS PLB User Manual Page 13