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The International Cospas-Sarsat Programme is a
satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
-aided
search and rescue Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search ...
(SAR) initiative. It is organized as a
treaty A treaty is a formal, legally binding written agreement between actors in international law. It is usually made by and between sovereign states, but can include international organizations An international organization or international o ...
-based,
nonprofit A nonprofit organization (NPO) or non-profit organisation, also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collective, public or social benefit, in co ...
, intergovernmental,
humanitarian Humanitarianism is an active belief in the value of human life, whereby humans practice benevolent treatment and provide assistance to other humans to reduce suffering and improve the conditions of humanity for moral, altruistic, and emotional ...
cooperative of 45 nations and agencies (see infobox). It is dedicated to detecting and locating emergency locator radio beacons activated by persons, aircraft or vessels in distress, and forwarding this alert information to authorities that can take action for rescue.
Distress alert A distress signal, also known as a distress call, is an internationally recognized means for obtaining help. Distress signals are communicated by transmitting radio signals, displaying a visually observable item or illumination, or making a soun ...
s are detected, located and forwarded to over 200
countries A country is a distinct part of the world, such as a state (polity), state, nation, or other polity, political entity. It may be a sovereign state or make up one part of a larger state. For example, the country of Japan is an independent, so ...
and
territories A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal. In international politics, a territory is usually either the total area from which a state may extract power resources or an ...
at no cost to beacon owners or the receiving government agencies. Cospas-Sarsat was conceived and initiated by
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
,
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
, the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, and the former
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
in 1979. The first rescue using the technology of Cospas-Sarsat occurred on . The definitive agreement of the organization was signed by those four States as the "Parties" to the agreement on 1 July 1988. The term Cospas-Sarsat derives from COSPAS (КОСПАС), an acronym for the Russian words "Cosmicheskaya Sistema Poiska Avariynyh Sudov" (Космическая Система Поиска Аварийных Судов), which translate to "Space System for the Search of Vessels in Distress". SARSAT is an acronym for Search And Rescue Satellite-Aided Tracking.


Background

Cospas-Sarsat is best known as the system that detects and locates emergency beacons activated by aircraft, ships and people engaged in recreational activities in remote areas, and then sends these distress alerts to
search-and-rescue Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search ...
(SAR) authorities. Distress beacons capable of being detected by the Cospas-Sarsat System (currently 406-MHz beacons) are available from several manufacturers and vendor chains. Cospas-Sarsat does not make or sell beacons. Between September 1982 and December 2021 the Cospas-Sarsat System provided assistance in rescuing at least 54,413 people in 17,663 SAR events. In 2019, 2020 and 2021 (the latest year for which statistics have been compiled), Cospas-Sarsat assistance included the following: These statistics under-count the number of events where Cospas-Sarsat assisted, because they only include cases when an accurate report from SAR personnel is provided back through reporting channels to the Cospas-Sarsat Secretariat. Cospas-Sarsat does not undertake search-and-rescue operations. This is the responsibility of national administrations that have accepted responsibility for SAR in various geographic regions of the world (typically the same geographic area as their
flight information region In aviation, a flight information region (FIR) is a specified region of airspace in which a flight information service and an alerting service (ALRS) are provided. The International Civil Aviation Organization (ICAO) delegates which country is re ...
). Cospas-Sarsat provides alert data to those authorities. Cospas-Sarsat cooperates with
United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and international security, security, develop friendly relations among nations, achieve international cooperation, and be ...
-affiliated agencies, such as the
International Civil Aviation Organization The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international sc ...
(ICAO), the
International Maritime Organization The International Maritime Organization (IMO, French: ''Organisation maritime internationale'') is a specialised agency of the United Nations responsible for regulating shipping. The IMO was established following agreement at a UN conference ...
(IMO), and the
International Telecommunication Union The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...
(ITU), among other international organizations, to ensure the compatibility of the Cospas-Sarsat distress alerting services with the needs, the standards and the applicable recommendations of the global community. Cospas-Sarsat is an element of the IMO's
Global Maritime Distress Safety System The Global Maritime Distress and Safety System (GMDSS) is a worldwide system for automated emergency signal communication for ships at sea developed by the United Nations' International Maritime Organization (IMO) as part of the SOLAS Conventio ...
(GMDSS), and is expected to become a component of ICAO's Global Aeronautical Distress and Safety System (GADSS). The IMO requires automatic-activating Cospas-Sarsat beacons (
EPIRB An Emergency Position-Indicating Radio Beacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats, a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in need of i ...
s, see below) on all vessels subject to requirements of the
International Convention for the Safety of Life at Sea The International Convention for the Safety of Life at Sea (SOLAS) is an international maritime treaty that sets minimum safety standards in the construction, equipment and operation of merchant ships. The International Maritime Organization ...
(so-called SOLAS-class vessels), commercial fishing vessels, and all passenger ships in international waters. Similarly, ICAO requires Cospas-Sarsat beacons aboard aircraft on international flights. National administrations often impose requirements in addition to the international requirements of those agencies. Cospas-Sarsat only monitors for alerts from
digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals **Digital camera, which captures and stores digital i ...
distress beacons that transmit on 406 MHz (so-called 406 beacons). Older beacons that transmit using the legacy
analog signal An analog signal or analogue signal (see spelling differences) is any continuous signal representing some other quantity, i.e., ''analogous'' to another quantity. For example, in an analog audio signal, the instantaneous signal voltage varies c ...
on 121.5 MHz or 243 MHz rely on being received only by nearby aircraft or rescue personnel. For satellite reception of alerts by Cospas-Sarsat the beacon must be a model that transmits at 406 MHz. Cospas-Sarsat has received many honors for its humanitarian work, including induction into the
Space Foundation The Space Foundation is an American nonprofit organization whose mission is to advocate for all sectors of the global space industry through space awareness activities, educational programs, and major industry events. It was founded in 1983. Loca ...
's Space Technology Hall of Fame for space technologies improving the quality of life for all humanity.


System operation

The system consists of a
ground segment A ground segment consists of all the ground-based elements of a space system used by operators and support personnel, as opposed to the space segment and user segment. The ground segment enables management of a spacecraft, and distribution of p ...
and a
space segment The space segment of an artificial satellite system is one of its three operational components (the others being the user and ground segments). It comprises the satellite or satellite constellation and the uplink and downlink satellite links. The ...
that include: * Distress radio-beacons to be activated in a life-threatening emergency *SAR signal repeaters (SARR) and SAR signal processors (SARP) aboard
satellites A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotop ...
*Satellite
downlink In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shar ...
receiving and signal processing
ground stations A ground station, Earth station, or Earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft (constituting part of the ground segment of the spacecraft system), or reception of radio waves fro ...
called LUTs (local user terminals) * Mission control centres (MCCs) that distribute to
rescue coordination centre A rescue co-ordination centre (RCC) is a primary search and rescue facility in a country that is staffed by supervisory personnel and equipped for co-ordinating and controlling search and rescue operations. RCCs are responsible for a geographic are ...
s distress alert data (particularly beacon location data) generated by the LUTs *
Rescue coordination centre A rescue co-ordination centre (RCC) is a primary search and rescue facility in a country that is staffed by supervisory personnel and equipped for co-ordinating and controlling search and rescue operations. RCCs are responsible for a geographic are ...
s (RCCs) that facilitate coordination of the SAR agency and personnel response to a distress situation.


Beacons

A Cospas-Sarsat
distress beacon An Emergency Position-Indicating Radio Beacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats, a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in need of i ...
is a
digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals **Digital camera, which captures and stores digital i ...
406-MHz radio transmitter that can be activated in a life-threatening emergency to summon assistance from government authorities. Beacons are manufactured and sold by dozens of vendors. They are classified in three main types. The beacons designed for use in an aircraft is known as an emergency locator transmitter (ELT). One designed for use aboard a marine vessel is called an emergency position-indicating radio beacon (
EPIRB An Emergency Position-Indicating Radio Beacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats, a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in need of i ...
). And one that is designed to be carried by an individual is known as a personal locator beacon (PLB). Sometimes PLBs are carried aboard aircraft or vessels, but whether this satisfies safety requirements depends on local regulations. A Cospas-Sarsat beacon does not transmit until it is activated in an emergency (or when certain testing features are activated by the user). Some beacons are designed to be manually activated by a person pressing a button, and some others are designed for automatic activation in certain circumstances (e.g., ELTs may be automatically activated by a physical shock, such as in a crash, and EPIRBs may be automatically activated by contact with water). There are ''no'' subscription or other costs imposed by Cospas-Sarsat for beacon ownership or use. (Some countries may impose licensing and/or registration charges for beacon ownership, and some jurisdictions may assess costs for rescue operations.) See below for recent beacon innovations.


Space segment

The Cospas-Sarsat system operational space segment consists of SARR and/or SARP instruments aboard: *Five satellites in polar low-altitude Earth orbit with LEOSAR (low-altitude Earth orbit search-and-rescue) payloads *Eleven satellites in geostationary Earth orbit with GEOSAR (geostationary Earth orbit search-and-rescue) payloads *More than 50 satellites in medium-altitude Earth orbit with MEOSAR (medium-altitude Earth orbit search-and-rescue) payloads A SARR or SARP instrument is a
secondary payload Secondary payload, also known as rideshare payload, is a smaller-sized payload transported to orbit on a launch vehicle that is mostly paid for—and with the date and time of launch and the orbital trajectory determined—by the entity that cont ...
and associated
antennas In radio engineering, an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies a ...
attached to those satellites as an adjunct to the primary satellite mission. A SARR instrument retransmits a beacon distress signal to a satellite ground station in real time. A SARP instrument records the data from the distress signal so that the information can later be gathered by a ground station when the satellite passes overhead.


Ground segment

The satellites are monitored by receiving ground stations (LUTs) equipped to track (point at and follow) the satellites using
satellite dish A satellite dish is a dish-shaped type of parabolic antenna designed to receive or transmit information by radio waves to or from a communication satellite A communications satellite is an artificial satellite that relays and amplifies radi ...
es or phased antenna arrays. LUTs are installed by individual national administrations or agencies. The distress messages received by a LUT are transferred to an associated mission control centre which uses a detailed set of computer
algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specificat ...
s to route the messages to rescue coordination centres worldwide.


System architecture

When a distress beacon is activated, the Cospas-Sarsat system: *decodes the
binary code A binary code represents text, computer processor instructions, or any other data using a two-symbol system. The two-symbol system used is often "0" and "1" from the binary number system. The binary code assigns a pattern of binary digits, also ...
d message of the beacon, which contains information such as the identity of the vessel/aircraft and, for beacons equipped with the feature, the location of the beacon derived from a local navigation source (such as a
GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
receiver incorporated into the beacon's design). *performs a mathematical analysis of the signal to calculate the location of the beacon, even if the beacon's location is not reported in the distress message. The Cospas-Sarsat system is the only satellite distress alerting system that is capable of this dual, redundant means of locating an activated distress beacon. The SARR and/or SARP instrument typically is attached to a satellite that is being launched primarily for another purpose. The primary mission of all of the LEOSAR and GEOSAR satellites is
meteorological Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...
(gathering of weather data). The primary mission of all of the MEOSAR satellites is
navigation Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
.


LEOSAR

LEOSAR (Low Earth Orbiting Search and Rescue) was the original Cospas-Sarsat
space segment The space segment of an artificial satellite system is one of its three operational components (the others being the user and ground segments). It comprises the satellite or satellite constellation and the uplink and downlink satellite links. The ...
architecture. The complementary LEOSAR-satellite orbits provide periodic coverage of the entire Earth. Because of their relatively low altitude (and therefore, relatively small "
footprint Footprints are the impressions or images left behind by a person walking or running. Hoofprints and pawprints are those left by animals with hooves or paws rather than feet, while "shoeprints" is the specific term for prints made by shoes. They ...
" of visibility of any particular part of the Earth at any given time), there are intervals of time when a LEOSAR satellite may not be over a particular geographic location. So there can be a delay in receiving an alert signal, and a delay in relaying that signal to the ground. For this reason, LEOSAR satellites are equipped with the "
store-and-forward Store and forward is a telecommunications technique in which information is sent to an intermediate station where it is kept and sent at a later time to the final destination or to another intermediate station. The intermediate station, or node in ...
" SARP modules in addition to "
real-time Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...
" SARR modules. The satellite can pass over a remote area of the Earth and receive a distress message, and then forward that data later when it passes into view of a ground station (that typically are located in less remote areas). The five satellites in the LEOSAR constellation have approximately 100 minute orbits. Because of their polar orbits the latency between satellite passes overhead is smallest at the poles and higher latitudes. The Cospas-Sarsat LEOSAR system was made possible by Doppler processing. LUTs detecting distress signals relayed by LEOSAR satellites perform mathematical calculations based on the Doppler-induced frequency shift received by the satellites as they pass over a beacon transmitting at a fixed frequency. From the mathematical calculations, it is possible to determine both bearing and
range Range may refer to: Geography * Range (geographic), a chain of hills or mountains; a somewhat linear, complex mountainous or hilly area (cordillera, sierra) ** Mountain range, a group of mountains bordered by lowlands * Range, a term used to i ...
with respect to the satellite. The range and bearing are measured from the rate of change of the received frequency, which varies both according to the path of the satellite in space and the rotation of the Earth. This allows a computer
algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specificat ...
to trilaterate the position of the beacon. A faster change in the received frequency indicates that the beacon is closer to the satellite's
ground track A ground track or ground trace is the path on the surface of a planet directly below an aircraft's or satellite's trajectory. In the case of satellites, it is also known as a suborbital track, and is the vertical projection of the satellite's or ...
. When the beacon is moving toward or away from the satellite track due to the Earth's rotation, the Doppler shift induced by that motion also can be used in the calculation.


GEOSAR

Because their geostationary orbit does not provide a relative motion between a distress beacon and a GEOSAR (Geostationary Search And Rescue) satellite, there is no opportunity to use the Doppler effect to calculate the location of a beacon. Therefore, the GEOSAR satellites only can relay a beacon's distress message. If the beacon is a model with a feature to report its location (e.g., from an on-board
GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
receiver) then that location is relayed to SAR authorities. While the inability to independently locate a beacon is a drawback of GEOSAR satellites, those satellites have an advantage in that the present constellation well covers the entire Earth in real time, except for the polar regions.


MEOSAR

The most recent
space segment The space segment of an artificial satellite system is one of its three operational components (the others being the user and ground segments). It comprises the satellite or satellite constellation and the uplink and downlink satellite links. The ...
augmentation for Cospas-Sarsat is MEOSAR (Medium Earth Orbiting Search and Rescue). MEOSAR blends the advantages of the LEOSAR and GEOSAR systems, while avoiding the drawbacks. Over time there will be more than 70 MEOSAR satellites, and the MEOSAR system will become the dominant space-segment capability of Cospas-Sarsat. In addition to the large number of satellites, the MEOSAR system benefits from relatively large satellite
footprints Footprints are the impressions or images left behind by a person walking or running. Hoofprints and pawprints are those left by animals with hoof, hooves or paws rather than foot, feet, while "shoeprints" is the specific term for prints made by ...
and sufficient satellite motion relative to a point on the ground to allow the use of Doppler measurements as part of the method of calculating a distress beacon's location. MEOSAR consists of SARR transponders aboard the following navigation-satellite constellations: the
European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...
's
Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...
,
Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
's
Glonass GLONASS (russian: ГЛОНАСС, label=none, ; rus, links=no, Глобальная навигационная спутниковая система, r=Global'naya Navigatsionnaya Sputnikovaya Sistema, t=Global Navigation Satellite System) is ...
, and the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
'
Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
(GPS). In November 2022, China became the newest MEOSAR space-segment provider, with Cospas-Sarsat SAR payloads aboard
six 6 is a number, numeral, and glyph. 6 or six may also refer to: * AD 6, the sixth year of the AD era * 6 BC, the sixth year before the AD era * The month of June Science * Carbon, the element with atomic number 6 * 6 Hebe, an asteroid People ...
of its
BeiDou The BeiDou Navigation Satellite System (BDS; ) is a Chinese satellite navigation system. It consists of two separate satellite constellations. The first BeiDou system, officially called the BeiDou Satellite Navigation Experimental System and ...
(BDS) navigation spacecraft. The first SAR-equipped BDS spacecraft was launched on 19 September 2018, and the last on 23 November 2019. Operational distribution of MEOSAR alert data began at 1300 UTC on 13 December 2016. This operational phase of MEOSAR is known as the early operational capability (EOC), and is being carried out with continued testing and adjustment in preparation for an initial operational capability (IOC) phase expected to be declared early in 2023. The MEOSAR system advances the ability to provide near-instantaneous detection, identification, and location-determination of 406-MHz beacons. Prior to the operational introduction of MEOSAR, MEOSAR data was successfully used to assist in determining the crash location of
EgyptAir flight 804 EgyptAir Flight 804 was a regularly scheduled international passenger flight from Paris Charles de Gaulle Airport to Cairo International Airport, operated by EgyptAir. On 19 May 2016 at 02:33Egypt Standard Time (UTC+02:00, UTC+2), the Airbus A32 ...
in the Mediterranean Sea. The location of a distress beacon is calculated by the receiving LUT by analyzing the frequency-difference-of-arrival (related to Doppler-induced variations), and/or the time-difference-of-arrival of a beacon's radio signal due to the differences in distance between the beacon and each MEOSAR satellite that may be in view. With respect to GPS-hosted payloads, experimental
S-band The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the conventional ...
payloads aboard 18 GPS Block IIR and
GPS Block IIF GPS Block IIF, or GPS IIF is an interim class of GPS (satellite), which are used to keep the Navstar Global Positioning System operational until the GPS Block IIIA satellites become operational. They were built by Boeing, to be operated by the U ...
satellites, and four payloads aboard
GPS Block IIIA GPS Block III (previously Block IIIA) consists of the first ten GPS III satellites, which will be used to keep the Navstar Global Positioning System operational. Lockheed Martin designed, developed and manufactured the GPS III Non-Flight Sat ...
satellites are used operationally by the Cospas-Sarsat System.
GPS Block IIIF GPS Block IIIF, or GPS III Follow On (GPS IIIF), is the second set of GPS Block III satellites, consisting of up to 22 space vehicles. The United States Air Force began the GPS Block IIIF acquisition effort in 2016. On 14 September 2018, a manu ...
satellites are planned to have dedicated, operational
L-band The L band is the Institute of Electrical and Electronics Engineers (IEEE) designation for the range of frequencies in the radio spectrum from 1 to 2 gigahertz (GHz). This is at the top end of the ultra high frequency (UHF) band, at the lower en ...
SAR payloads, with launches beginning around 2026. The GPS SAR system is known as the ''Distress Alerting Satellite System'' (DASS) by
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...
. Additionally, the Galileo component of the MEOSAR system is able to download information back to the distress radio-beacon by encoding "Return Link Service" messages into the Galileo navigation data stream. It can be used to activate an indicator on the beacon to confirm receipt of the distress message.


Ground segment

As at December 2019 the LEOSAR satellites are tracked and monitored by 60 commissioned LEOLUT (low-altitude Earth-orbit local user terminals) antennas, the GEOSAR satellites by 25 commissioned GEOLUT antenna

and the MEOSAR satellites by 24 commissioned MEOLUT stations, each having multiple antennas. The data from these earth stations is transferred to and distributed by 32 MCC
established globally
of which 3 remain under development. (See infobox for the countries and agencies that are ground-segment providers.)


Beacons

There has been one transmission
modulation In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains informatio ...
method used by Cospas-Sarsat beacons since their inception more than 30 years ago, binary
phase-shift keying Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency reference signal (the carrier wave). The modulation is accomplished by varying the sine and cosine inputs at a ...
(BPSK), with two allowed bit-string lengths: 112 (with 87 bits of message information) and 144 (with 119 bits of message information). Several message protocols are allowed in the available message-bit string to accommodate different kinds of beacons (ELTs, EPIRBs and PLBs), different vessel/aircraft identifiers, and different national requirements. The time length of these transmissions is approximately one-half second. These
narrowband Narrowband signals are signals that occupy a narrow range of frequencies or that have a small fractional bandwidth. In the audio spectrum, narrowband sounds are sounds that occupy a narrow range of frequencies. In telephony, narrowband is usua ...
transmissions occupy approximately 3 kHz of
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...
in a channelized scheme across the assigned 406.0 to 406.1 MHz band. Cospas-Sarsat is in the process of specifying a new, additional beacon modulation and message scheme based on
spread-spectrum In telecommunication and radio communication, spread-spectrum techniques are methods by which a signal (e.g., an electrical, electromagnetic, or acoustic signal) generated with a particular bandwidth is deliberately spread in the frequency doma ...
technology with quadrature
phase-shift keying Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency reference signal (the carrier wave). The modulation is accomplished by varying the sine and cosine inputs at a ...
(QPSK). Presently beacons that will use this scheme are termed "second generation" beacons. This technology will allow the use of battery-saving lower-power transmissions, improve the accuracy of the determination of the beacon location by the Cospas-Sarsat System, and avoid the need for discrete channelization in the assigned 406.0 to 406.1 MHz band (e.g., avoiding the need for periodic closing and opening of channels by Cospas-Sarsat for use by beacon manufacturers based on narrowband channel loading). Second-generation beacons will have a longer transmission period of one second, with 250 transmitted bits, 202 of those being message bits. Additionally, the information sent in the message bits from one transmission to the next can be changed on a rotating transmission schedule ("rotating message fields") to allow significantly more information to be communicated over the course of a series of transmission bursts. In response to recent commercial aviation disasters and new ICAO requirements for autonomous tracking of aircraft in distress, Cospas-Sarsat has finalized specifications for ELTs for distress tracking (ELT(DT)s) to meet the ICAO requirements. Whereas present ELTs are designed to activate on impact or by manual activation by the flight crew, ELT(DT)s will activate autonomously when an aircraft enters threatening flight configurations that have been predetermined by expert agencies. In this way, ELT(DT)s will allow a plane in distress to be tracked in-flight, prior to any crash, without human intervention aboard the aircraft. ELT(DT)s have been specified using both the existing beacon transmission method (narrowband BPSK) and the second-generation (spread-spectrum QPSK) modulation schemes. Cospas-Sarsat capability for receiving and processing distress messages from ELT(DT)s using the narrowband BPSK transmission method has been declared operational effective 1 January 2023. Declaration for ELT(DT)s using the spread-spectrum QPSK modulation method is expected early in 2023.


History


First Legal framework

On 23 November 1979, a " memorandum of understanding concerning cooperation in a joint experimental satellite-aided search and rescue project" was signed in Leningrad, USSR, among the U.S. National Aeronautics and Space Administration, the USSR Ministry of Merchant Marine, the
Centre National d'Etudes Spatiales The (CNES; French: ''Centre national d'études spatiales'') is the French government space agency (administratively, a "public administration with industrial and commercial purpose"). Its headquarters are located in central Paris and it is und ...
of France, and the Department of Communications of Canada. Under Article 3 of the memorandum, it was stated that: "Cooperation will be achieved through effecting interoperability between the SARSAT project and the COSPAS project at 121.5MHz, 243MHz and in the 406.0 – 406.1 MHz band and conducting of tests, mutual exchange of test results and preparation of a joint report. The objective of this cooperation is to demonstrate that equipment carried on low-altitude, near polar-orbiting satellites can facilitate the detection and location of distress signals by relaying information from aircraft and ships in distress to ground stations, where the information processing is completed and passed to rescue services." "This joint Project will permit the Parties to make recommendations on follow-on global applications."


Development

The first system satellite, "COSPAS-1" ( Kosmos 1383), was launched from
Plesetsk Cosmodrome Plesetsk Cosmodrome ( rus, Космодром «Плесецк», r=Kosmodrom "Plesetsk", p=kəsmɐˈdrom plʲɪˈsʲet͡sk) is a Russian spaceport located in Mirny, Arkhangelsk Oblast, about 800 km north of Moscow and approximately 200&n ...
on June 29, 1982. Cospas-Sarsat began tracking the two original types of distress beacons, EPIRBs and ELTs, in September, 1982. The first persons were rescued with the assistance of Cospas-Sarsat when the distress signal from a small plane was relayed by the COSPAS-1 satellite to a then-experimental ground station in Ottawa, Ontario, Canada. The story has been related by the plane's pilot, Jonathan Ziegelheim, who rescue authorities judged would probably have died of his injuries if it were not for Cospas-Sarsat. Prior to the founding of Cospas-Sarsat, the civilian aviation community had already been using the 121.5 MHz frequency for distress, while the military aviation community utilized 243.0 MHz as the primary distress frequency with the 121.5 MHz frequency as an alternate. In each case, detection of the distress signal relied on reception by aircraft passing nearby, and localization of the signal was done with Earth-based
direction finding Direction finding (DF), or radio direction finding (RDF), isin accordance with International Telecommunication Union (ITU)defined as radio location that uses the reception of radio waves to determine the direction in which a radio station ...
equipment. Satellites made it possible to expand this "local" search paradigm into a global capability. Each of the four founding Party States took responsibility for one of the major tasks in the project. The United States (with project leadership from NASA's
Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C. in Greenbelt, Maryland, United States. Established on May 1, 1959 as NASA's first space flight center, GSFC empl ...
in Greenbelt, MD, USA) directed Datron Systems in Chatsworth, CA, USA to design and build LUT
ground stations A ground station, Earth station, or Earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft (constituting part of the ground segment of the spacecraft system), or reception of radio waves fro ...
to receive the
downlink In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shar ...
from the satellites. At Datron, a team designed a LUT with five
horn antenna A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguide shaped like a horn to direct radio waves in a beam. Horns are widely used as antennas at UHF and microwave frequencies, above 300 MHz. They are us ...
s, and Jeffrey Pawlan designed the downconverter and the specialized
monopulse Monopulse radar is a radar system that uses additional encoding of the radio signal to provide accurate directional information. The name refers to its ability to extract range and direction from a single signal pulse. Monopulse radar avoids prob ...
receiver capable of locking onto the downlink from the satellites. France and Canada were responsible for the data generation and decoding. They designed the computer that determined the approximate position of the beacon from the Doppler shift of the beacon's signal caused by the relative motion of the beacon and the receiving satellite. The former Soviet Union was responsible for the design and construction of the first satellite to be launched. Engineers from all four countries met in Moscow in February 1982 to successfully test the operational functionality of all of the equipment together in the same laboratory. The Party States led development of the 406-MHz marine
EPIRB An Emergency Position-Indicating Radio Beacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats, a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in need of i ...
, that used a digital messaging scheme, for detection by the system. The EPIRB was seen as a key advancement in SAR technology in the perilous maritime environment. The digital message allowed the beacon and its associated vessel to be uniquely identified. Early in its history, the Cospas-Sarsat system was engineered to detect beacon-alerts transmitted at 406 MHz, 121.5 MHz and 243.0 MHz. Because of a large number of false alerts, and the inability to uniquely identify such beacons because of their old, analogue technology (that provided no message, only a tone indicating distress), the Cospas-Sarsat system beginning in 2009 stopped receiving alerts from beacons operating at 121.5 MHz and 243.0 MHz, and now only receives and processes alerts from modern, digital 406-MHz beacons. Many ELTs include both a 406-MHz transmitter for satellite detection and a 121.5 MHz transmitter that can be received by local search crews using direction-finding equipment. In the early 2000s (in 2003 in the USA) a new type of distress beacon, the personal locator beacon (PLB), became available for use by individuals who cannot contact
emergency services Emergency services and rescue services are organizations that ensure public safety and health by addressing and resolving different emergencies. Some of these agencies exist solely for addressing certain types of emergencies, while others deal wit ...
through normal telephone-originated services, such as
1-1-2 112 is a common emergency telephone number that can be dialed free of charge from most mobile telephones, and in some countries, fixed telephones in order to reach emergency services (ambulance, fire and rescue, police). 112 is a part of the ...
or
9-1-1 , usually written 911, is an emergency telephone number for the United States, Canada, Mexico, Panama, Palau, Argentina, Philippines, Jordan, as well as the North American Numbering Plan (NANP), one of eight N11 codes. Like other emergency nu ...
. Typically PLBs are used by people engaged in recreational activities in remote areas, and by small-aircraft pilots and mariners as an adjunct to (or, when permitted, a substitute for) an ELT or EPIRB. The design of distress beacons as a whole has evolved significantly since 1982. The newest 406-MHz beacons often incorporate global navigation satellite system (GNSS) receivers (such as those using
GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
). Such beacons determine their location using the internal GNSS receiver (or a connection to an external navigation source) and transmit in their distress message highly accurate position reports. This provides a second method for Cospas-Sarsat to know the location of the distress, in addition to the calculations independently done by Cospas-Sarsat LUTs to determine the location. The distress alert received by the satellites and the beacon location contained in the message and/or calculated from the distress signal are forwarded almost instantly to SAR agencies by Cospas-Sarsat's extensive international data-distribution network. This two-tiered reliability and global coverage of the system has inspired the current motto of SAR agencies: "Taking the 'Search' out of Search and Rescue." COSPAS (КОСПАС) is an
acronym An acronym is a word or name formed from the initial components of a longer name or phrase. Acronyms are usually formed from the initial letters of words, as in ''NATO'' (''North Atlantic Treaty Organization''), but sometimes use syllables, as ...
for the
Russian Russian(s) refers to anything related to Russia, including: *Russians (, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *Rossiyane (), Russian language term for all citizens and peo ...
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 An acronym is a word or name formed from the initial components of a longer name or phrase. Acronyms are usually formed from the initial letters of words, as in ''NATO'' (''North Atlantic Treaty Organization''), but sometimes use syllables, as ...
for Search And Rescue Satellite-Aided Tracking.


References


External links


Official Website for the International Cospas-Sarsat Programme

International Astronautical Federation, "The History and Experience of the International Cospas-Sarsat Programme for Satellite-Aided Search and Rescue"

Official Website for the USA's Sarsat Program


* * {{Coord, 41, 08, 04, N, 16, 50, 04, E, type:landmark_source:kolossus-itwiki, display=title Maritime communication Emergency communication Rescue Soviet and Russian space institutions Canada–Soviet Union relations International telecommunications Soviet Union–United States relations France–Soviet Union relations Intergovernmental organizations established by treaty