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COSPAS-SARSATSearch and RescueSystem

1) Beacon Activated due to

grave and imminent danger

2) Distress signals received by

COSPAS-SARSAT satellites

3) Alerts re-transmitted to auto-

mated ground stations called

Local User Terminals (LUTs)

4) Mission Control Centers(M CCs)

receive alerts from LUTs,

process the signals and

forward them to RCCs

(NOAA operates U.S.MCC)

5) Rescue Control Centers (RCCs)verify distress and alertnearest Search and Rescueunits

6) Search and Rescue unitsgo to t he scene and takecare of victims

The difference between 121.5 MHz and 406 MHz emergency beacons:

BEACON TYPE 121.5 M Hz 406 MHzBeacon Identif ication None Unique ID number

Locat ion Accuracy 12 miles 2 miles

Coverage Local Global

Signal Power 0.1 Watt 5 Watt s

Signal Type Analog Digit al

Alert Time (minimum) 2 hours Inst antaneous

Doppler Locat ion Tw o Passes Single Pass

GPSLocation None 100m Accuracy

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Search and rescue satellites save livesIn September 1982 another milestone in the historyof space was made when t he fi rst emergency distressbeacon signal from a downed aircraft was picked upby a low earth-orbiting satellite. Three people weresaved. Today, over 20 years later, the number of res-

cues* attr ibut ed to the existence of search and rescuesatellites number in the thousands worldwide.

This search and rescue satellit e system , called COSPAS-SARSAT, is international in scope, operates 24 hours aday, 7 days a week and is free of charge to anyonein distress. The National Oceanic and AtmosphericAdministration (NOAA) is responsible for operatingand maintainin g the system in t he U.S.. NOAA workswit h t he U.S. Coast Guard for mariti me search andrescue (SAR) incidents and the U.S. Air Force forinland SAR incidents. It has proven to be an indis-pensable too l fo r search and rescue in t he UnitedStates and around the wo rld.

How emergency distress beacons workEmergency distress beacons are essentially specializedradio t ransmit ter s. Search and rescue satellit es,

thou sands of miles above the earth, can " hear" evenfaint distress signals radiating up f rom t hese beacons;signals that might not otherwise be heard by land-based receivers or over-flying aircraft. Knowingthere is a distress and gett ing t here fast is vital bothto survivors and rescue personnel. It can mean thediff erence betw een life and death. Emergencybeacons provide that capabilit y. For example, asatellite would hear a downed aircraft's distressbeacon in most cases, before the plane was evenreported overdue.

* A rescue is recorded any ti me COSPAS-SARSAT is used as the primar y 

means of alerting or locating during a rescue 

Different types for different applicationsThere are three types of distress beacons: EPIRBs(Emergency Positioning Indicating Radio Beacons)for use in the maritime community, ELTs (EmergencyLocator Transmitters) found on aircraft and PLBs(Personal Locator Beacons) for i ndividual u se. EPIRBs

and ELTs are capable of automat ic activati on, w herePLBs can only be set off manually.

121.5 MHz distress frequency to

be dropped – Remember this date! 

At present there are two internationally sanctionedsatellit e alertin g di stress frequencies - 406 MHz(digital) and 121.5 MHz (analog). Older modelEPIRBs and ELTs send a distress signal on only121.5 MHz, which is little more than a homingsignal. The newer, more advanced, models sendout an encoded, digital 406 MHz frequency, whichprovides more accurate location and identif icationinformation. PLBs are only available with 406 MHz capabilities .

Import ant changes are coming soon f or 121.5 MHz

model beacon own ers. As of February 1, 2009,the 121.5 MHz frequency band will no longer beprocessed by search and rescue satellit es. Thedecision t o dro p pro cessing of 121.5 MHz w as madeby t he Intern ational Cospas-Sarsat Program wit hguidance from the United Nations. This was due tonumerous signal receptio n pro blems, a high incidenceof f alse alerts (over 99%) and a host of o ther limit -ations associated w ith the 121.5 MHz frequ ency.

Why just 406 MHz?When search and rescue satellit es were fir st launched,the digital 406 MHz frequency was introduced towor k specifically wit h the system. In addition , the121.5 MHz analog distress frequency band was alsoincluded due to its widespread use in aviation.Although it was initially a giant step forward insearch and rescue, 121.5 MHz soon proved unreliable

and prone to false alerts...and its limitations continueto t his day.

It’s all about time & location

NOAA’s satellit es detect hundreds of 121.5 MHz“hits” per day. 99% of t hem are false. False alertsare generated many ways. Some culprits includeATM machines, sports stadium scoreboards, and pizzaovens! Because of this unreliability, a 121.5 MHz

hit must be independently verified to make sure thatit is a real distress. This means delays in respondingto calls for help whil e Rescue Coordin ation Centers(RCCs) work t o verify that t he distress is real. Poorsignal strengt h f rom a 121.5 MHz beacon also meanspoor accuracy. Search areas can be as large as12 to 15 nautical miles in radius, a lot of t erritoryfor search and rescue teams to cover and verytime consuming.

406 MHz beacons, on the ot her hand, have provensuperior perfor mance capabiliti es. They transmit amuch stronger signal, are more accurate, verif iableand tr aceable. 406 MHz distress signals can be accu-rately detected within a matter of minutes. Each406 MHz beacon has a unique ID encoded wit hin it ssignal. As long as the beacon ID has been registered

(which is required by law), RCCs can quickly confirmthat the distress is real, who they are looking for andwh ere they should lo ok. This means a search can belaunched even before a f inal distress location hasbeen determined. Positio n accuracy means thesearch area is less than 2 nautical miles in radius,which decreases the amount of time SAR teamsmust search. This adds up to a significant t imesaving and a major advantage over the 121.5 MHzbeacons.

406 beacons and GPS

Some 406 MHz beacon models have been designedwit h the capabilit y to util ize GPSt echnology. If the406 MHz beacon carri es a GPS receiver, eith erinternally or externally connected, then the location

of t he distress can be know n instantaneously andis even more accurate – to wit hin 100 yards!

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