Search and Rescue Satellite System
Artist's concept of the spacecraft
1976: Dr. Alan Winter with prototype emergency beacon.
1981: SARSAT Local User Terminal (LUT) at CRC received signals from activated emergency beacons relayed by U.S. weather satellites and Soviet COSPAS satellites. The signals were then sent to the Search and Rescue Centre at Trenton.
Newspaper clipping, 1982.
1982: Soviet COSPAS satellite relayed the emergency beacon signal from this crash site in British Columcia, enabling a search and rescue team to go to the aid of the three occupants. This was the first satellite-aided rescue from an aircraft crash. The downed aircraft is in the approximate centre of the photo.
Detail of the crash site.
Harvey Werstiuk, 1970
CRC Photo 70-19946
Alan Winter, 1973
CRC Photo 73-27674
Searching for downed aircraft is time-consuming and costly in a country the size of Canada. The rapid detection and location of an aircraft crash or marine distress is of paramount importance to the potential survivors and to the search and rescue teams charged with effecting the rescue. Studies have shown that even those who survive an initial aircraft crash incident have less than a 10% chance of survival if the rescue is delayed beyond two days. In contrast, if the rescue can be accomplished within eight hours, their survival rate is over 50%. Furthermore, rapid location can significantly reduce both search and rescue costs and the length of exposure of search and rescue teams to hazardous conditions frequently encountered during search and rescue operations.
The use of special purpose radio frequency transmitters, automatically activated by the aircraft crash or the marine distress, offer the possibility of dramatically shortening the time required to alert rescue forces to the distress and to assist in final "homing" by the rescue team. The use of these Emergency Locator Transmitters (ELTs) and their marine equivalent Emergency Position Indicating Radio Beacons (EPIRBs) had grown rapidly during the decade leading up to the SARSAT program. At the time, there were over 200,000 ELTs and 6,000 EPIRBs in operation just in the United States.
Both the aviation ELTs and the maritime EPIRBs transmit a distinct "wow-wow" modulated tone signal on one or both of the emergency distress frequencies of 121.5 and 243 MHz. These signals can provide both an immediate alert and a homing signal to assist rescue forces in locating the site of the distress - if someone is listening. Before SARSAT, detection of these signals depended largely on the voluntary monitoring of the distress channels by overflying aircraft. This voluntary system of detection provided irregular coverage at best, with the largest gaps in coverage in remote regions where the need for rapid response to an accident is most acute. The COSPAS-SARSAT project provided the potential for worldwide monitoring of the distress frequency bands.
The SARSAT concept involves the use of multiple satellites in low, near-polar orbits "listening" for distress transmissions. The signals received by the satellites are relayed to a network of dedicated ground stations where the location of the emergency is determined by measuring the Doppler shift between the satellite, with a precisely known orbit, and the distress signal. This information is then relayed to a Mission Control Centre (MCC) which alerts the appropriate Rescue Coordination Centre (RCC). The RCC then begins the actual search and rescue operation in accordance with conventional practice.
Within this general concept two experiments were conducted. The first was designed to serve aircraft and vessels currently equipped with commercially available emergency transmitters operating at 121.5 and 243 MHz. This service is limited, however, by the non-optimum characteristics of these transmitters. The second experiment using transmitters operating at 406 MHz and designed specifically for satellite detection will provide improved capability. In addition to working with existing ELT/EPIRBs at 121.5 (and 243 MHz in the case of SARSAT), a capability to investigate operations with experimental ELT/EPIRB test units operating in the assigned emergency band at 406 MHz was also included.
In the SARSAT system, a repeater on board the spacecraft relays the 121.5 and 243 MHz and 406 MHz signals directly to a Local User Terminal (LUT). At the LUT, special processing is used to extract the weak 121.5 MHz/243 MHz signals from the noise, recover the Doppler information, and determine the ELT/EPIRB position. The 406 MHz ELT/EPIRB test unit signals are handled in the same way except that the signal strength and format is designed to permit the use of less sophisticated processing techniques. The COSPAS system does not relay the 243 or 406 MHz bands.
A fundamental requirement of the concept was to have it work with existing ELT/EPIRBs operating at 121.5 and 243 MHz. They were not designed with satellite detection in mind. Doppler positioning using the relative motion between the spacecraft and the ELT/EPIRB was chosen as the only practical means of locating these very simple devices. All that is required is that the ELT/EPIRB emit a carrier frequency with a reasonable stability during the duration of satellite visibility. To optimize Doppler-positioning performance, a low-altitude polar orbit is used. The low altitude results in low ELT/EPIRB power requirements, good Doppler-shift characteristics and short time delays between successive passes. The polar orbit also results in coverage of the whole earth.
Discussions were initiated regarding the possibility of a joint experimental program which culminated in the signing of a Memorandum of Understanding in 1979 between Canada, the United States and France to create the Search and Rescue Satellite-Aided Tracking, or SARSAT program. A second Memorandum of Understanding signed in 1980 and resulted in the addition of the Soviet Union. This created what is now known internationally as the COSPAS-SARSAT program. September 9, 1982 was the first demonstration of the effectiveness of the SARSAT system.
The Department of National Defence (DND) tasked CRC to investigate the possibility of using satellite in the search and rescue of plane crashes and shipwrecks. Canada was not the only country trying to reach the same goal. France and the United States were conducting research in the same area. Discussions between the three countries led to a Memorandum of Understanding in 1979 to create SARSAT. As well, the Soviet Union was conducting its own research. In 1980, the Soviet Union signed a Memorandum of Understanding between the other three countries. They were conducting at that time a similar project called COSPAS. Since this agreement, the Search and Rescue Satellite-Aided Tracking program has been known as the COSPAS-SARSAT program. The Soviets used COSPAS satellites, while SARSAT transponders were flown on U.S. TIROS weather satellites.
In the actual implementation of the program in Canada, DND delegated all technical responsibility to a Technical Project Office at CRC. This CRC office was responsible for all technical aspects of the Canadian portion of the international program, including the overall system design, sub-system specification, hardware development, equipment procurement, pre-launch support and post-launch testing. All of the hardware development and equipment procurement was carried out through industrial contracts which involved the following major activities:
- procurement of the search and rescue repeaters from SPAR Aerospace;
- development of the ground station signal processor, first with Miller Communication, which became a part of Calian Technology Ltd
- procurement of the Canadian ground station of Local User Terminal from Canadian Astronautics Ltd. (CAL);
- procurement of the Canadian Mission Control Centre from SED Systems, which is now part of Calian Technology Ltd;
- development of 406 MHz distress beacon technology first with Hermes Electronics, then with Bristol Aerospace and finally with Microtel Pacific Research, which is now MPR Teltech Ltd.
Canada's international partners contributed modestly to the space science, technology and engineering as applied to the search and rescue system. The USA provided a platform for the SARSAT flight hardware by modifying some of the TIROS weather satellites, France provided a space-borne processor which was a variation on an existing French processor, and the USSR built compatible systems for flight on some of its COSPAS satellites based on SARSAT system specifications.
The first 15 months were part of a demonstration and evaluation phase to determine the system's effectiveness. Only nine days after testing began, on September 9, 1982, SARSAT demonstrated its effectiveness in searching for downed aircraft. On October 11, its effectiveness was demonstrated in relation to marine distress.
In 1995, the Canadian organizations and key individuals involved in the SARSAT project won the Canadian Aeronautics and Space Institute's Alouette Award. From almost any perspective, the COSPAS-SARSAT program has been a tremendous success for Canada. From an international perspective, Canada as one of the four founding countries, has been able to ensure not only that the evolving international system met our domestic requirements, but also that our industry was in a position to benefit from the new market opportunities. The COSPAS/SARSAT project has contributed to the saving of approximately 3500 lives world-wide since its operational inception in 1982.
The SARSAT project established Canada as an international leader in associated technologies, and resulted in direct industry export sales exceeding $50M in associated search and rescue systems and considerably more in spin-off applications of the technology to other space projects. Personal Locator Beacons (PLB) were developed by MPR Teltech Ltd., for use by individuals in the North.
Alan Winter conducted feasibility research, while Harvey Werstiuk served as technical manager. In addition to his important role as director general, Bert Blevis also played a key role in international negotiations. Many other employees from CRC worked on this important project.
Only nine days after testing began, on September 9, 1982, the Ottawa ground station detected distress signals relayed by COSPAS I from an airplane crash in northern British Columbia. The location co-ordinates supplied by COSPAS-SARSAT enabled searchers to find the airplane in a mountain valley 90 km off its planned route. Three injured survivors were rescued by Canadian Forces personnel.
On October 11, 1982, the trimaran "Gonzo" capsized during a storm 480 km east of Boston. The emergency transmitter signal was picked up by airliners on transoceanic routes, but the exact location was not determined until the COSPAS satellite passed over the site. U.S. and Canadian ground stations located the vessel and a U.S. Coast Guard patrol vessel rushed to the scene. Three people were rescued. This was the first marine rescue using data from the COSPAS-SARSAT system.
From Alouette to Anik and Beyond: Canada Celebrates its First 20 years in Space. (Pamphlet) Ottawa; D.O.C., 1982, 12 pp.
Lyrette, Jacques. "The Role of Satellites in Search and Rescue." Presentation given to the Canadian Conference on Electrical and Computer Engineering. Halifax; prepared by E.J. Hayes, 1994.
Page created on July 2, 1996 by Cynthia Boyko
Page last updated on February 6, 2001 by Stu McCormick
Copyright © Friends of CRC, 1997.