User's Manual

system that utilizes Russian Federation and

United States’ low altitude, near-polar orbiting

satellites (LEOSAR). These satellites assist in

detecting and locating activated 406 MHz satel-

lite beacons.

COSPAS and SARSAT satellites receive dis-

tress signals from EPIRBs transmitting on the

frequency of 406 MHz. The COSPAS-SARSAT

406 MHz beacon signal consists of a transmis-

sion of non-modulated carriers followed by a dig-

ital message format that provides identication

data. The 406 MHz system uses Satellite-borne

equipment to measure and store the Doppler-

shifted frequency along with the beacon’s 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 satel-

lite, as well as being stored for later transmission to other LUTs.

The LUT processes the Doppler-shifted signal from the LEOSAR and determines the loca-

tion 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 dis-

tress alert to any of the LUT stations. When there is GPS data included in the distress mes-

sage, SAR authorities instantly know your location to within 110 yards (100 m). 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.

8.3 Global Positioning System (GPS)

The GPS system is a satellite group that enables a GPS receiver to determine its exact posi-

tion to within 30 m (100 ft.) 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 infor-

mation on position, velocity, and time anywhere in the world and in all weather conditions.

Fig ure 11 - G PS S ate llite

O rbits

Figure 11 - GPS Satellite Orbits

Figure 10 - GEOSAR Satellite Orbits