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SEARCH
AND RESCUE SATELLITES
Low-Earth Orbiting Search And Rescue
(LEOSAR) Satellites
·
NOAA Polar Orbiting Environmental
Satellites (POES) – known as ‘SARSAT’
·
Russian Nadezhda Satellites – known
as ‘COSPAS’
Geostationary
Orbiting Search And Rescue (GEOSAR) Satellites
·
NOAA Geostationary Orbiting Environmental
Satellites (GOES)
·
ISRO Indian National Satellite (INSAT)
·
ESA Metosat Second Generation (MSG)
Low-Earth
Orbiting Search And Rescue (LEOSAR) Satellites
The keystone to the Cospas-Sarsat System are the low-earth orbiting
(LEO) satellites from which the system takes its name. These satellites
provide the ability to detect and locate 406 MHz alerts worldwide and 121.5
MHz alerts for about sixty percent of the world.
 SARSAT
is an instrument package flown aboard the NOAA series of environmental
satellites operated by NOAA's National Environmental Satellite, Data and
Information Service (NESDIS). These satellites orbit at an altitude of 528
miles and complete an orbit every 100 minutes. Their orbits are inclined 99
degrees from the equator. Typically, each satellite monitors the earth for
various weather and climate data.
Yet, each satellite also carries a Search and Rescue Repeater (SARR)
which receives and retransmits 121.5 MHz, 243 MHz, and 406 MHz signals
anytime the satellite is in view of a ground station. Also carried is a
Search and Rescue Processor (SARP) which receives 406 MHz transmissions,
provides measurements of the frequency and time, then retransmits this data
in real-time and stores it aboard for later transmission. The satellite
also stores each 406 MHz signal it receives and continuously downloads this
data for up to 48 hours ensuring ground stations around the world receive
it. That is, if the satellite
was not in view of a ground station when it received a beacon signal, the
next ground station that sees that satellite views will receive the data.
This provides global coverage for 406 MHz distress signals. The SARR is
provided by the Canadian Department of National Defence and the SARP is
provided by the French Center National D'Etudes Spatiales (CNES).
The COSPAS instrument is carried aboard the NADEZHDA navigation satellite
orbiting the Earth every 105 minutes at an altitude of 620 miles and an
orbital inclination of 83 degrees. The COSPAS instrument was built by the
former Soviet Union and
continues to be operated by the Russian
Federation. The only major
difference between COSPAS and SARSAT is that the Russian satellites do not
receive 243 MHz distress signals.
Geostationary
Orbiting Search And Rescue (GEOSAR) Satellites
 As you can see from this image
taken today from GOES-East, geostationary satellites are capable of
continually viewing large areas of the Earth. These geostationary (GEO)
satellites are also able to provide immediate alerting and identification
of 406 MHz beacons. The GEO satellites are not able to use Doppler
location processing since they have no relative motion between them and the
emergency beacons. Therefore, they are not able to determine a location for
a beacon. They can, however, provide immediate alerts. This is a valuable
tool for SAR personnel since it allows them to begin their initial verification
of the alert using the National 406 MHz Beacon Registration Database. Often
this detective work yields a general location of the vessel or aircraft in
distress and SAR assets can be readied or dispatched to that general area.
Ideally, a SARSAT or COSPAS (LEO) satellite will fly over the beacon within
the next hour and calculate a Doppler location which will be given to the
SAR personnel who may already be enroute.
There is also one
significant advantage with the GEOSAR constellation and that is the ability
to use a GPS receiver with a 406 MHz beacon. Here’s how it works: specially
made emergency beacons determine their location using a GPS receiver that
is either integrated into the beacon (called a location protocol beacon) or
fed by an external GPS receiver. This accurate location information
(generally around a football field in size for positional accuracy) is then
encoded into the 406 MHz signal that is transmitted by the beacon. The USMCC then receives that signal
with the location and notifies the RCC accordingly. This information can often be
derived in a matter of minutes!
Since every second counts in reaching the scene of a distress this
means that there is an increased chance of survival.
Without a doubt, the early
warning capability of the GEOSAR constellation provides a valuable tool to
increase the  effectiveness of the Cospas-Sarsat system and, ultimately, save
more lives.
Two important
considerations: First, a GPS-equipped beacon only works
when the receiver has a clear view of the sky in order to permit the
receiver to self-locate. Often
times, conditions do not permit this which may either distort the
positional accuracy or negate it altogether. Because of this, the Cospas-Sarsat
System relies upon the Doppler locating effect as the primary means for
locating a beacon. This process
is able to overcome the limitations of a GPS unit and still generate a
fairly accurate location…within a mile for positional accuracy. Secondly, the GEOSAR component only
works if the beacon is registered with NOAA. Without registration, the RCCs are
unable to react as quickly…and ultimately this may delay a SAR
response should you be in an emergency. If you have a 406 MHz beacon and
have not registered it, please do so by clicking here to
access the National 406 MHz Registration Database.
Status of Cospas-Sarsat LEOSAR Payload Instruments
(Last Updated 28
April 2005)
|
Satellite
|
Repeater
Instruments
|
SARP
|
Comments
|
|
121.5 MHz
|
243 MHz
|
406 MHz
|
Global
|
Local
|
|
|
Sarsat-6
|
NO
|
NO
|
NO
|
NO
|
NO
|
Decommissioned
|
|
Sarsat-7
|
F
|
L
|
F
|
F
|
F
|
Intermittent loss of service, which may affect an entire
or partial satellite pass.
|
|
Sarsat-8
|
L
|
NO
|
F
|
F
|
F
|
Intermittent loss of 121.5 MHz service
|
|
Sarsat-9
|
F
|
F
|
F
|
F
|
F
|
|
|
Sarsat-10
|
F
|
F
|
F
|
F
|
F
|
|
|
Cospas-9
|
NO
|
NA
|
NA
|
NO
|
NO
|
Decommissioned on
6 August 2007
|
Status of Cospas-Sarsat GEOSAR Payload Instruments
(Last Updated 28
April 2005)
|
Satellite
|
Status
|
Gain Control
|
Comments
|
|
GOES-East (75° W)
|
F
|
ALC
|
|
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GOES-West (135° W)
|
F
|
ALC
|
|
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INSAT 3A (93.5°
E)
|
L
|
TBD
|
INSAT 3A is currently under evaluation however, alerts
from the system are distributed operationally. INSAT system does not process
2nd protected field of long format messages.
|
|
MSG (0°)
|
F
|
Fixed
|
|
|
Legend
|
|
F
|
Fully Operational
|
L
|
Limited Operations
|
ALC
|
Automatic Level Control
|
|
NO
|
Not Operational
|
NA
|
Not Applicable
|
TBD
|
To Be Determined
|
|
|
|
UT
|
Under Test
|
|
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