SARSAT System Overview

System Overview

Search and Rescue (SAR) instruments are flown on low earth polar orbiting (LEO), medium earth orbiting (MEO) and geostationary earth orbiting (GEO) satellites provided by the U.S., Russian Federation, India and the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT). These instruments are capable of detecting signals coming from the Earth’s surface transmitted by emergency beacons.

The primary types of beacons are emergency locator transmitters (ELTs) used by the aviation community, emergency position indicating radio beacons (EPIRBs) used in the maritime environment, and personal locator beacons (PLBs) used mainly by individuals in multiple environments.

SARSAT Diagram

  1. ELTs, EPIRBs, and PLBs operate on the 406 MHz frequency.  Each 406 MHz beacon transmits a unique digital code that identifies the type of beacon and that allows registration data to be associated with the beacon.  The registration data provides information such as the beacon owner; the type of platform the beacon is associated with; emergency points of contact; and much more.
  2. After the satellite receives a beacon signal, it relays the signal to earth stations referred to as local user terminals (LUT). 
  3. The LUT processes the data, computes the location of the distress beacon, and transmits an alert message to its respective Mission Control Center (MCC) via a data communication network. 
  4. The MCC performs matching and merging of alert messages with other received messages, geographically sorts the data, and transmits a distress message to another MCC, an appropriate SAR authority such as a national Rescue Coordination Center (RCC) or a foreign SAR Point of Contact (SPOC).
  5. The RCC investigates the beacon alert and launches assets to find the parties in distress when necessary.

* Return Link Service (RLS) is a proposed future enhancement of the Cospas-Sarsat system

The United States MCC (USMCC) receives data from other MCCs and its LUTs and then transmits distress messages via a data communication network to one of the following U.S. national SAR services:

  • Two U.S. Air Force RCCs
  • Eleven U.S. Coast Guard RCCs
  • Special programs configured to receive alert messages
The USMCC also transmits distress messages internationally to SPOCs in other nations that are considered within the USMCC service area but outside of the U.S. Search and Rescue Region.