5.3.2 Independent Beacon Location
The Cospas-Sarsat Ground Segment includes a network of satellite ground stations, called Local User Terminals (LUTs), that are installed and operated by participating Ground Segment Provider States.
All the beacon messages that are received by a LEOLUT or a MEOLUT are sorted to identify the messages that are received from each distress beacon. The LUT then processes the time and frequency data and performs its location determination processing as follows:
· After each pass of the satellite over a LEOLUT[1], the LUT processes all of the data collected during that pass. It analyzes the change of the received frequency as the satellite passes over each beacon and uses this data to compute a Doppler location estimate for the beacon.
· A MEOLUT[2] processes all of the data received from each individual transmission from a beacon. It computes the time differences and frequency differences of these messages as they arrive at the LUT through each of the available satellite relay paths. It uses this information to compute a difference of arrival (DOA) location estimate for the beacon.
A GEOLUT[3] does not have any independent location capability; it can only produce unlocated alert detection messages unless the beacon itself provides an “encoded” location (derived from a navigation system such as the Global Positioning System (GPS)).
[1] The requirements for a LEOLUT are defined in document C/S T.002, “Cospas-Sarsat LEOLUT Performance Specification and Design Guidelines”. The LEOLUT commissioning tests are defined in document C/S T.005, “Cospas-Sarsat LEOLUT Commissioning Standard”.
[2] The requirements for a MEOLUT are defined in document C/S T.019, “Cospas-Sarsat MEOLUT Performance Specification and Design Guidelines”. The MEOLUT commissioning tests are defined in document C/S T.020, “Cospas-Sarsat MEOLUT Commissioning Standard”.
[3] The requirements for a GEOLUT are defined in document C/S T.009, “Cospas-Sarsat GEOLUT Performance Specification and Design Guidelines”. The GEOLUT commissioning tests are defined in document C/S T.010, “Cospas-Sarsat GEOLUT Commissioning Standard”.