Tuesday, January 27, 2009

Starting February 1, Cospas-Sarsat will discontinue monitoring the frequencies that are used for analog-based emergency position-indicating radio beacons (EPIRB), the 121.5 and 243 MHz frequencies. Search and rescue (SAR) groups worldwide will only monitor the 406 MHz frequency, which is dedicated to digital locators.

The 406 MHz digital band has many advantages over the older analog systems. Since the locators send data to satellites, rather than just provide a continuous signal, much more will be known about the emergency before a SAR group arrives, such as the type of vehicle and owner. In addition, the accuracy will be greatly enhanced from a 1400 square kilometre (500 square mile) search zone down to just 90m (100 yards) if the locator has a GPS fix. The most important reason for the switch is the reduction of false positives. With the older analog bands, only about one in every 50 alerts was real, whereas with the digital system that is reduced to about one in every 17 alerts being real.

With fewer false positives and greatly increased accuracy, SAR groups around the world will be better able and faster to respond to life-threatening emergencies within the critical “golden day”. They will also be able to do this with fewer wasted resources.

The phase-out of analog transponders has been a long time coming. The first warnings were sent by the US Coast Guard in 2000, and analog devices have not been manufactured in the last several years. For most large boats the cost of upgrading to the new system was negligible. The change February 1 is worldwide, with both the International Civil Aviation Organization and the International Maritime Organization recommending the switch.