What happens when you activate your PLB?

When you are in trouble and push the button on your beacon it is important that it has a clear view of the sky.  This allows the GPS receiver inside the beacon to begin acquiring data from the GPS satellite system, those coordinates are then incorporated into a powerful five watt signal transmitted into outer space on 406 megahertz (the international emergency frequency).  This signal is detected by three different satellite constellations;

• The LEOSAR (low-earth orbit search-and-rescue) satellite system
• The MEOSAR (medium-earth orbit search-and-rescue) satellite system
• The GEOSAR (geosynchronous search-and-rescue) satellite system

These satellites are part of the COSPAS/SARSAT system (an international satellite system for locating and rescuing persons in distress).  These satellites locate your personal locator beacon using a both a phenomenon known as doppler shift and from the GPS location data in the signal.

Now that the satellites know your position, they rebroadcast that alert message to a local user terminal (LUT) on earth.  The local user terminal immediately forwards the alert message along with the position data to the Mission Control Center (MCC).  Each beacon has a unique serial number and that serial number is matched to a database so they know who they are looking for.  That information is added to the alert message and it is forwarded on to the Alaska Rescue Coordination Center (AKRCC) in Anchorage.

When the AKRCC receives the alert message from the MCC they then know where you are and that you’re in trouble so they immediately begin coordinating with the NSB SAR coordinator to launch a rescue.  The NSB SAR coordinator determines if the local volunteer SAR from the nearest village, the rescue helicopter, or both are needed for the rescue.  The NSB SAR helicopter is equipped with a system that can track and locate your beacon using both the 121.5-megahertz homing signal in your beacon and the 406-megahertz signal to actually come to your location.