The beginnings of SARSAT date back to October 1972 when a plane carrying two U.S. congressmen crashed in a remote region of Alaska. A massive search and rescue effort was mounted, but to this day, no trace of them or their aircraft has ever been found. In reaction to this tragedy, Congress mandated that all aircraft in the United States carry an Emergency Locator Transmitter (ELT). This device was designed to automatically activate after a crash and transmit a homing signal.
Since satellite technology was still in its infancy, the frequency selected for ELT transmissions was 121.5 MHz, already in use as the international aircraft distress frequency. This system worked, but had many limitations. The frequency was cluttered, there was no way to verify who the signal was originating from, and most importantly, another aircraft had to be within range to receive the signal.
After several years, the limitations of analog ELTs began to outweigh their benefits. At that time, a satellite based system was conceived. It would operate on a frequency reserved only for emergency beacons (digital 406 MHz), it would have a digital signal that uniquely identified each beacon, and it would provide global coverage.
The SARSAT system was developed in a joint effort by the United States, Canada , and France. In the United States, the SARSAT system was developed by NASA. Once the system was functional, its operation was turned over to NOAA where it remains today.
As the system began to take hold, more and more emergency beacons found their way onto the market. ELTs continued to operate exclusively on analog 121.5 MHz, but maritime beacons (EPIRBs) were being built that operated on digital 406 MHz. The U.S. Coast Guard in their role as maritime search and rescue specialists immediately began to see the benefits of 406 MHz, and in 1990, took proactive steps to bring it into widespread usage. As a result, today there are over 156,000 EPIRBs in the NOAA 406 MHz Registration Database. With 406 MHz ELTs and PLBs the number of 406 MHz Emergency Beacons registered now totals over 240,000! Is your beacon registered too?
A similar system, COSPAS, was developed by the Soviet Union. The four nations, United States, Canada, France and the Soviet Union banded together in 1979 to form Cospas-Sarsat. In 1982, the first satellite was launched, and by 1984 the system was declared fully operational.
Although Cospas-Sarsat satellites were primarily designed to function on the much improved 406 MHz frequency, they still had to make a provision for the thousands of 121.5 MHz beacons already in use. For this reason, the satellites were designed to receive 121.5 MHz as well.
Since that time, however, the analog 121.5 MHz beacons have become a source of chronic false alerts. Furthermore, they are not as accurate or advanced as the improved digital 406 MHz beacons. Because of their continual problems a decision was made internationally in 2000 that on February 1, 2009 the Cospas-Sarsat satellites would no longer detect any 121.5 MHz beacons. At 12:00am Greenwich Mean Time (GMT) on that date, 121.5 MHz listening was turned off for all satellites.
The Cospas-Sarsat organization also continued to grow. The four original member nations have now been joined by 42 other nations, user states and organizations that operate 77 ground stations and 30 mission control centers worldwide, or serve as Search and Rescue Points of Contact (SPOCs). Cospas-Sarsat continues to be a model of international cooperation. During the eighties, the Soviet Union and the United States were able to put aside their Cold War differences and tackle some tough technical questions. Today, new technology continues to evolve and the member nations are actively incorporating that technology into The Cospas-Sarsat System of Tomorrow.