(The graphic below and portions of the text on this page courtesy of NASA and NOAA)
1. In situations
of “grave and imminent danger” when lives are at risk, emergency
beacons are activated.
alerts received by the satellites are retransmitted to 38 automatic
(unstaffed) ground stations worldwide. These stations are called
Local User Terminals (LUTs).
3. Alerts are
routed to a Mission Control Center (MCC) in the country that operates
the LUT. Routed messages include beacon location computed at the
LUT if the message is received by one of the system's low-Earth-orbiting
satellites. Alerts received by system satellites in geosynchronous
orbit provide instantaneous alerting and can include location information
if the beacon is a self-locating type (using GPS or onboard navigation).
4. After validation
processing, alerts are relayed depending on beacon location or country
of registration (406 MHz beacons only) to either another MCC or
to the appropriate Rescue Coordination Center (RCC).
5. U.S. RCCs
are operated by the Coast Guard and the Air Force. The Air Force
Rescue Coordination Center (AFRCC) at Tyndall AFB, Florida, coordinates
all inland SAR activities in the lower 48 states. In most situations,
the actual search and rescue is carried out by the Civil Air Patrol
or local rescue services. The U.S. Coast Guard coordinates and conducts
most maritime SAR missions from RCCs located in nine Command Districts
around the United States and two Rescue Sub-Centers (RSCs) in San
Juan, Puerto Rico, and in Guam. Alaskan inland rescues are handled
differently. The Air Force operates an Alaskan Rescue Coordination
Center (AKRCC) in Anchorage at Ft. Richardson. Alaskan SAR is carried
out by Air National Guard units, the Alaska State Police, and local
The U.S. portion
of the COSPAS-SARSAT system is operated by the NOAA SARSAT Office
in Suitland, Maryland. The U.S. Mission Control Center (USMCC) is
COSPAS-SARSAT is an international, humanitarian satellite-based
search and rescue system that has helped save over 20,000 lives worldwide
since its inception in 1982 (total as of June 2005).
SARSAT is an acronym for Search and Rescue Satellite-Aided
Tracking. COSPAS is an acronym for the Russian words "Cosmicheskaya
Sistyema Poiska Avariynich Sudov," which mean "Space System
for the Search of Vessels in Distress," indicative of the maritime
origins of this distress alerting system.
The system, which operates 24 hours a day, 365 days a year, detects and
locates transmissions from emergency beacons carried by ships, aircraft,
and individuals. Use of the COSPAS-SARSAT system is FREE to the beacon operator.
Sponsored by Canada, France, Russia, and the United States, the system
aims to reduce the time required to alert rescue authorities whenever
a distress situation occurs. The rapid detection and location of a downed
aircraft, a ship, or an individual in distress are of paramount importance
to survivors and to rescue personnel.
The COSPAS-SARSAT system consists of emergency radio beacons (distress beacons), equipment
on satellites in low-Earth polar or in geosynchronous orbits, ground receiving
stations also called Local User Terminals (LUTs), Mission Control Centers
(MCCs), and Rescue Coordination Centers (RCCs).
There are three types of emergency beacons: 1) Emergency Position Indicating
Radio Beacons (EPIRBs) for maritime applications, 2) Emergency Locator
Transmitters (ELTs) for aviation applications, and 3) Personal Locator
Beacons (PLBs) for individuals in distress. Emergency beacons may transmit on
121.5, 243.0 (military) and 406 MHz. Satellite notification
of 121.5 MHz alerts are being phased out in the near future 406 MHz has become
the international standard providing far better accuracy and fewer false alert search initiations.
Beacons that transmit on 406 MHz send digitally encoded information which
includes a beacon I.D. for accessing a user registration database. This
database can supply the beacon type, its country of origin, and the registration
number of the maritime vessel or aircraft and can also include location
data derived from the Global Positioning System (GPS). Encoded location
is of great value when using a geostationary (GEO) satellite for relaying
beacon signals because a GEO satellite provides immediate alerting.
contacts provided in the registration allow the RCC to confirm the
validity of the alert and may also improive emergency forces response.
The system uses two different types of satellites: polar-orbiting satellites
in low-Earth orbit (LEO) and satellites in geosynchronous orbit. Russia
and the United States provide the LEO satellite platforms. Canada, France,
Russia, and the United States contribute components. The Russian NADEZHDA
navigation satellites carry the COSPAS repeater packages, and NOAA weather
satellites carry Sarsat packages. The NOAA LEO satellites orbit the Earth
every 100 minutes. COSPAS satellites complete an orbit every 105 minutes.
GEO satellites continually view large areas of the Earth from approximately
70 degrees North to 70 degrees South latitudes and can provide immediate
alerting and identification of 406 MHz beacons. GEO satellites are operated by the
United States, India and the European Union
Even though GEO satellites
cannot determine a beacon's location using Doppler processing, the near
instantaneous alerting (3 - 5 minutes) with the user I.D., and detective work by the RCC often yield
the location of the distress call. Based on this information alone, search
planning can begin. Ideally, a SARSAT or COSPAS LEO satellite will overfly
the beacon within the next hour and confim with a Doppler-determined location.
via the LEO satellites provides a location within 2 miles. If the
beacon is equipped with GPS or receives a location from onboard
navigation equipment, this encoded location is tranmitted to the GEO
satellite, providing immediate location information accurate to within
The COSPAS-SARSAT LEO system uses two modes of operation. In the Bent-Pipe
or repeater mode, the Search and Rescue Repeater, or SARR, immediately
retransmits received beacon signals to any LUT in the satellite's footprint.
This mode is possible when the spacecraft is visible to both the beacon
and the ground station simultaneously, an area approximately 2,500 miles
(4,000 km) in diameter. In the store and forward mode, the on-board processor,
or SARP, receives and records search and rescue beacon transmissions and
repeatedly retransmits them to LUTs as the satellite orbits the Earth.
This mode is possible only with 406 MHz beacons. It provides true global
The signals received by LEO satellites are relayed to a network of LUTs
that locate the beacon by measuring the Doppler shift caused by the motion
of the satellite with respect to the beacon. This process can locate beacons
within an accuracy of approximately 12.4 miles (20 km) for 121.5 MHz beacons and of
approximately 3 miles (5 km) for 406 MHz beacons. (A low-power 121.5 MHz homing signal
included in all U.S. 406 MHz beacons helps rescuers determine the final
location as they approach, when necessary.)
The location data is then relayed to an MCC that alerts the appropriate
RCC or an MCC in another country. If the alert is in an area covered by
a foreign MCC, that MCC is alerted, and in turn, notifies its own RCC.
The RCC then begins the actual search and rescue operation.
NOAA, the U.S. Coast Guard, and the U.S. Air Force operate the COSPAS-SARSAT
system in the United States. NASA provides technical support by investigating
system problems and developing technological improvements.
More information may be found at: http://www.sarsat.noaa.gov/