Since the inception of Cospas-Sarsat in 1982, distress radiobeacons have assisted in the rescue of over 22,000 people in more than 6,000 distress situations.^[3] In 2006, distress radiobeacons aided in the rescue of 1,881 people in 452 distress situations.^[3] There are roughly 556,000 121.5 MHz beacons and 429,000 406 MHz beacons.^[4] As of 2002, there were roughly 82,000 registered (406 MHz) beacons, and over 500,000 of the older unregistered kind.^{[citation needed]}

Civil Air Patrol members practice searching for an emergency locator transmitter. The member in front is using a manual radio direction finder.

(more at the link from Wikipedia. Alan Spicer’s note – I guess it’s more useful of a game than some might think, the game of Locating a Radio Transmitter in a large area – often played as a contest by Amateur Radio Operators!!!!)

http://en.wikipedia.org/wiki/GEOSAR

Cospas-Sarsat

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The current logo for Cospas-Sarsat

Cospas-Sarsat is an international satellite-based search and rescue (SAR) distress alert detection and information distribution system, established by Canada, France, the United States, and the former Soviet Union in 1979.

The system consists of both a ground segment and a space segment:

• Distress radiobeacons
• SAR signal processors aboard satellites
• Satellite downlink receiving and signal processing stations called LUTs (local user terminals)
• Mission Control Centres that distribute distress alert data generated by the LUTs
• Rescue Coordination Centres that coordinate SAR response to a distress situation

The space segment of the Cospas-Sarsat system currently consists of SAR processors aboard 4 geosynchronous satellites called GEOSARs and 5 low-earth polar orbit satellites called LEOSARs.[1]

[edit] Background information

Cospas-Sarsat began tracking the two original types of distress radiobeacons in 1982. Specifically, these were:

• EPIRBs (Emergency Position-Indicating Radio Beacons), which signal maritime distress; and
• ELTs (Emergency Locator Transmitters), which signal aircraft distress

More recently, a new type of distress radiobeacon became available (in 2003 in the USA) [2]:

• PLBs (Personal Locator Beacons), are for personal use and are intended to indicate a person in distress who is away from normal emergency services (i.e. 9-1-1)

The four founding countries led development of the 406 MHz marine EPIRB for detection by the system. The EPIRB was seen as a key advancement in SAR technology in the perilous maritime environment. The aviation community had already been using the 121.5 MHz frequency for distress, so ELTs for general aviation were created using 121.5 MHz, a frequency listened to by the airlines. Military beacons using the 243.0 MHz frequency could also be detected by the system.

The design of distress radiobeacons as a whole has evolved significantly since 1982; the newest 406 MHz beacons incorporate GPS receivers; such beacons transmit highly accurate positions of distress almost instantly to SAR agencies via the GEOSAR satellites. The advent of such beacons has created the current motto of SAR agencies — “Taking the ‘Search’ out of Search and Rescue.” (See MEOSAR below.) [3]

COSPAS (КОСПАС) is an acronym for the Russian words “Cosmicheskaya Sistema Poiska Avariynyh Sudov” (Космическая Система Поиска Аварийных Судов), which translates to “Space System for the Search of Vessels in Distress”. SARSAT is an acronym for Search And Rescue Satellite-Aided Tracking.^[1]

Cospas-Sarsat is an element of the Global Maritime Distress Safety System (GMDSS). Automatic-activating EPIRBs are now required on International Convention for the Safety of Life at Sea (SOLAS) ships, commercial fishing vessels, and all passenger ships, are designed to transmit to a Rescue Coordination Centre a vessel identification and an accurate location of the vessel from anywhere in the world.

[edit] Phase-out of 121.5 & 243.0 MHz distress radiobeacons

Starting on 1 February 2009, the Cospas-Sarsat System stopped processing signals from the deprecated 121.5 MHz and 243 MHz beacons; now only signals from 406 MHz beacons are processed.^[2] The switch to 406 MHz is expected to result in a substantial reduction in wasted use of SAR resources on false alerts while simultaneously increasing the responsiveness of the system for real distress cases.

[edit] System composition

The ground segment of the system consists of:

• Distress radiobeacons
• Satellite downlink receiving and signal processing stations called local user terminals (LUT)
• Mission Control Centres that distribute distress alert data generated by the LUTs
• Joint Rescue Coordination Centers (also referred to as Rescue Coordination Centres) that coordinate SAR response to a distress situation

The space segment of the system consists of:

• SAR signal processors aboard satellites

[edit] Space segment (SAR processors)

The Cospas-Sarsat system space segment consists of SAR signal processors (SARP) aboard:

• 4 geosynchronous satellites called GEOSARs, and
• 5 low-earth polar orbit satellites LEOSARs.[4]

A SARP is basically a box attached to the side of a satellite.[5] In this way, SARP are considered a secondary payload onboard satellites with more lucrative core purposes. See the Technical Information below for lists of SARP and their associated satellites.

[edit] Ground segment

The satellites are monitored by receiving stations equipped with satellite-tracking satellite dishes called local user terminals (LUT). Each nation’s LUTs are monitored by an MCC (Mission Control Centre), a data distribution clearinghouse that distributes alert information to the various Joint Rescue Coordination Centers.

[edit] Technical information

[edit] Doppler processing

The Cospas-Sarsat system was made possible by the advent of Doppler processing. LUTs detecting non-geostationary satellites profit from the apparent Doppler frequency shift heard by LEOSAR and MEOSAR satellites as they pass over a beacon transmitting at a fixed frequency. The apparent frequency shift allows processing to triangulate the position of the distress radiobeacon. See Doppler Processing article at Cospas-Sarsat and Wiki on Doppler radar.

[edit] LEOSAR

Example of LEOSAR signal footprint.

LEOSAR predates the GEOSAR system, and it complements it. LEOSAR satellites are monitored by 44 LEOLUTs (low Earth orbit local user terminals).^[3] The complementary LEOSAR satellites provide periodic coverage of the entire earth with an emphasis on polar regions. The LEOSAR satellites operate in a store-and-forward mode for 406 MHz signals — they store distress signals and forward them to the next LEOLUT ground station they overfly. The 4-satellite polar-orbit constellation LEOSAR system provides frequent coverage of the poles with approximately 100 minute orbits.

Up until mid-2007, two of the LEOSAR satellites were Cospas satellites provided by the former Soviet Union and operated by the Russian Federation. However, they were recently taken offline, and now, the American NOAA Polar Operational Environmental Satellites (POES) and the EUMETSAT MetOp-A are the only LEOSAR satellites in service. COSPAS satellites characteristically orbit at 1000 km altitude.

The five operational LEOSAR satellites are the Sarsat satellites provided by the United States NOAA. These orbit at an altitude of 850 km. They are: ^[4]

• Sarsat-7 SARP aboard NOAA-15
• Sarsat-8 SARP aboard NOAA-16
• Sarsat-9 SARP aboard NOAA-17
• Sarsat-10 SARP aboard NOAA-18
• Sarsat-11 SARP aboard METOP-A

[edit] GEOSAR

The GEOSAR satellites are monitored by 16 GEOLUTs (Geostationary Earth Orbit Local User Terminals.) ^[5] The GEOSAR satellites provide continuous coverage of the entire earth below 70 degrees latitude with a view toward the equatorial sky. Some locations have poor radio reception toward the GEOSAR satellites and polar regions are not well covered.

SARP are installed on the following geostationary satellites: ^[6]

• The GOES geostationary satellites GOES-East at 75° W and GOES-West at 135° W
• The INSAT-3A geostationary satellite at 93.5° E
• The Meteosat Second Generation (MSG) geostationary satellites MSG-1 at 9.5° E and MSG-2 fixed over the Prime Meridian

[edit] Beacon technical information

Main article: Distress radiobeacons

Typical rescue beacon radios transmit a 5 watt signal for 0.5 second once every 50 seconds. Most of these terminals sold since 1997 include a GPS receiver so they can report precise GPS lat-lon location. Aircraft distress radiobeacons (ELTs) are automatically activated by acceleration switches after a crash, while maritime radiobeacons (EPIRBs) are normally activated by contact with sea water.

The “406 MHz” channel is 170 kHz wide and centered at 406.05 MHz. The message is either a 112-bit “short” message or a 144-bit “long” message both including 49 bits of identification plus position information.

[edit] MEOSAR

DASS MEOSAR Logo

Supporters of the Cospas-Sarsat system are working to add a new capability called MEOSAR (Medium Earth Orbit Search and Rescue satellites.) In its current (project) form, it is being called the Distress Alerting Satellite System (DASS) by NASA.^[7] This system will put SAR processors aboard the GPS satellite constellation and the Galileo positioning system constellation. MEOSAR satellites will be able to provide near-instantaneous detection, identification, receipt of encoded position, and determination of Doppler triangulated position of 406 MHz beacons (exclusively.) MEOSAR assets will report signals from Cospas-Sarsat search and rescue beacons in the 406.0–406.1 MHz band.^[8] There is also the possibility that the system will be able to download information back to the distress radiobeacon via the GPS downlink.^[7]

[edit] Rescue statistics

In 2006, the Cospas-Sarsat system provided assistance in rescuing 1,881 people in 452 SAR events.[6]

[edit] References

1. ^ Cospas-Sarsat. “Cospas-Sarsat Acronyms / Definitions“. http://www.cospas-sarsat.org/Management/acronyms.htm. Retrieved 2007-09-24. 
2. ^ Cospas-Sarsat. “Cospas-Sarsat Phase-Out of 121.5/243 MHz Alerting Services“. http://www.cospas-sarsat.org/FirstPage/121.5PhaseOut.htm. Retrieved 2007-09-24. 
3. ^ Summary Status
4. ^ http://www.cospas-sarsat.org/DocumentsSystemDataDocument/SD32-DEC06.pdf
5. ^ GEOLUT Description
6. ^ Space Segment Status
7. ^ ^{a b} NASA Search and Rescue Mission Office : Distress Alerting Satellite System (DASS)
8. ^ ESA Portal – Improving Daily Life – Galileo to support global search and rescue

[edit] External links

• Official website for the International Cospas-Sarsat Programme
• Official website for the USA’s Sarsat Program
• Detailed SARSAT and COSPAS satellite information
• Lay Person Explanation of the Satellite System
• Official website for Techno-Sciences, Inc. SARSAT program

Retrieved from “http://en.wikipedia.org/wiki/Cospas-Sarsat#GEOSAR“

Categories: Maritime communication | Maritime emergency | Emergency communication | Rescue | Law of the sea