System Concept
 The
basic Cospas-Sarsat concept is illustrated in the adjacent figure. The
System is composed of:
-
distress radiobeacons (ELTs for aviation use, EPIRBs for maritime
use, and PLBs for personal use) which transmit signals during distress
situations;
-
instruments on board satellites in geostationary
and low-altitude Earth orbits which
detect the signals transmitted by distress radiobeacons;
-
ground receiving stations, referred to as Local Users Terminals
(LUTs), which receive and process the satellite downlink signal
to generate distress alerts; and
- Mission Control Centers (MCCs) which receive alerts
produced by LUTs and forward them to Rescue Coordination Centers (RCCs),
Search and Rescue Points Of Contacts (SPOCs) or other MCCs.
The Cospas-Sarsat System includes two types of satellites:
- satellites in low-altitude Earth orbit (LEO) which form the LEOSAR
System
- satellites in geostationary Earth orbit (GEO) which form the GEOSAR
System
 Cospas-Sarsat
has demonstrated that the GEOSAR and LEOSAR system capabilities are
complementary. For example the GEOSAR system can provide almost immediate
alerting in the footprint of the GEOSAR satellite, whereas the LEOSAR
system:
-
provides coverage of the polar regions (which are beyond the coverage
of geostationary satellites);
-
can calculate the location of distress events using Doppler processing
techniques; and
-
is less susceptible to obstructions which may block a beacon signal
in a given direction because the satellite is continuously moving
with respect to the beacon.
LEOSAR and GEOSAR Capabilities
|
Channel Processing
|
LEOSAR
|
GEOSAR
|
|
406 MHz
|
- Beacon identification information and location
information provided
- Global coverage, but not instantaneous
|
- Beacon identification provided, and location
information available if encoded in beacon message (location
protocol beacon)
- Near instantaneous alerting in the GEOSAR
coverage area
|
|
121.5 MHz
|
- Beacon location information available
- Beacon identification not provided
- Local mode coverage only
|
Not supported
|
Processing of 121.5 MHz beacons will terminate on 1 February 2009 |
|
