Problems in the emergency beacon network

When voyagers purchase and register an EPIRB, they have a reasonable expectation that should they activate the beacon, the Sarsat system will swing into gear and rescue them. And in many places around the world, that expectation is well-founded. Two recent cases of EPIRB activation, however, suggest that even the best, most reliable EPIRB might not help you in an emergency.

- TIM QUEENEY

The EPIRB on your boat is the user element of an international system called Cospas-Sarsat. This system — developed by the U.S., the USSR (after the breakup of the USSR, Russia continued to participate), France and Canada — began in 1979 as an agreement between the four nations for a satellite-based system for aiding downed aircraft and mariners in distress. Transceivers were first included onboard low Earth orbit (LEO) polar-orbiting weather satellites. These transceivers pick up the signals from EPIRBs and emergency locator transmitters (ELTs) on aircraft and retransmit them down to Earth stations. Later, similar Sarsat transceivers were added to geostationary satellites and to GPS, GLONASS and Galileo medium Earth orbit (MEO) navigation satellites. The result is that 54 satellites are listening for EPIRB and ELT signals, and together provide coverage for the entire globe.

The Earth stations, called local user terminals (LUTs), send the distress signals to 34 mission control centers (MCCs) around the world. The MCCs evaluate the case and then send the info to the appropriate Rescue Coordination Center (RCC). These are the facilities that actually dispatch search and rescue (SAR) vessels and aircraft to find and assist the boat in distress or downed aircraft.

In general, the system works very well and has a long history of successful rescues. With the advent of 406-MHz EPIRBs that can broadcast their GPS-derived positions, the system has gotten even better and more precise.