03-12-2012, 06:41 PM
A SEARCH AND RESCUE SATELLITE SYSTEM
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ABSTRACT:
Countries use satellites in many areas such as military, navigation, search and rescue, etc. In this paper we have dealt with one of the newest search and rescue satellite system – THE COSPAS-SARSAT SYSTEM. It is an international search and rescue system made up of a network of satellites in space and control centres on Earth-ground stations, mission control centres and rescue coordination centres.
Search and rescue satellites are designed to provide a way for vessels at sea and in the air to communicate from remote areas. These satellites can detect and locate emergency beacons carried by ships, aircrafts, or individuals in remote or dangerous places.
Satellites equipped with search and rescue equipment (transmitter) fly over a beacon that is releasing an emergency signal. Using mathematical calculations involving the Doppler Effect, scientists can translate that signal into coordinates and determine the location of the distress signal within four kilometers.
In the eyes of countries using the COSPAS-SARSAT system, this system has very much helped the search and rescue efforts.
INTRODUCTION:
The SARSAT system was developed in a joint effort by the United States, Canada and France. The COSPAS system was developed by the Soviet Union. These four nations banded together in 1979 to form Cospas-Sarsat. In 1982, the first Cospas-Sarsat satellite was launched and by 1884 the system was declared fully operational. From there, the Cospas-Sarsat organization continued to grow.
SYSTEM CONCEPT:
The basic Cospas-Sarsat concept is illustrated in the figure below:
The system is composed of:
Distress radiobeacons (ELTs for aviation use, EPRIBs 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 User 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.
406 MHz LEOSAR LOCAL MODE:
When the satellite receives 406 MHz beacon signals, the on-board Search and Rescue Processor (SARP) recovers the digital data from the beacon signal, measures the Doppler frequency shift and time-tags the information. The result of this processing is formatted as digital data which is transferred to the satellite downlink for transmission to any LEOLUT in view. This data is also simultaneously stored on the spacecraft for later transmission and ground processing in the global coverage mode.
In addition to the 406 MHz local mode provided by the 406 MHz SARP instrument, a 406 MHz repeater, on Sarsat satellites only, can also provide a 406 MHz local mode operation. The difference between the SARP and the repeater is that the SARP performs some of the processing on board the satellite, whereas the repeater simply reflects the beacon signal to the earth, thereby requiring additional processing on the ground.
[attachment=42354]
ABSTRACT:
Countries use satellites in many areas such as military, navigation, search and rescue, etc. In this paper we have dealt with one of the newest search and rescue satellite system – THE COSPAS-SARSAT SYSTEM. It is an international search and rescue system made up of a network of satellites in space and control centres on Earth-ground stations, mission control centres and rescue coordination centres.
Search and rescue satellites are designed to provide a way for vessels at sea and in the air to communicate from remote areas. These satellites can detect and locate emergency beacons carried by ships, aircrafts, or individuals in remote or dangerous places.
Satellites equipped with search and rescue equipment (transmitter) fly over a beacon that is releasing an emergency signal. Using mathematical calculations involving the Doppler Effect, scientists can translate that signal into coordinates and determine the location of the distress signal within four kilometers.
In the eyes of countries using the COSPAS-SARSAT system, this system has very much helped the search and rescue efforts.
INTRODUCTION:
The SARSAT system was developed in a joint effort by the United States, Canada and France. The COSPAS system was developed by the Soviet Union. These four nations banded together in 1979 to form Cospas-Sarsat. In 1982, the first Cospas-Sarsat satellite was launched and by 1884 the system was declared fully operational. From there, the Cospas-Sarsat organization continued to grow.
SYSTEM CONCEPT:
The basic Cospas-Sarsat concept is illustrated in the figure below:
The system is composed of:
Distress radiobeacons (ELTs for aviation use, EPRIBs 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 User 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.
406 MHz LEOSAR LOCAL MODE:
When the satellite receives 406 MHz beacon signals, the on-board Search and Rescue Processor (SARP) recovers the digital data from the beacon signal, measures the Doppler frequency shift and time-tags the information. The result of this processing is formatted as digital data which is transferred to the satellite downlink for transmission to any LEOLUT in view. This data is also simultaneously stored on the spacecraft for later transmission and ground processing in the global coverage mode.
In addition to the 406 MHz local mode provided by the 406 MHz SARP instrument, a 406 MHz repeater, on Sarsat satellites only, can also provide a 406 MHz local mode operation. The difference between the SARP and the repeater is that the SARP performs some of the processing on board the satellite, whereas the repeater simply reflects the beacon signal to the earth, thereby requiring additional processing on the ground.