ACR&Artex Float-Free 406 Memory Capsule - Manual (Page 20)

Y1-03-0199 Rev. E 17
SECTION 7 - THE SEARCH AND RESCUE SYSTEM
7.1 General Overview
Memory capsule's provides distress alerting via radio transmission on 406 MHz to satellites of the Cospas-Sarsat
network. ACR's Float Free 406 Memory Capsule can also transmit a distress alert to the GEOSAR network that
includes GPS latitude and longitude coordinates that are inputted through an I/R Interface that connects to the data
output of a GPS Receiver.
The message transmitted is unique for each beacon, which provides identification of the transmitter through computer
access of registration files maintained by the National Oceanic and Atmospheric Administration or other National
Authority. Remember, if your beacon is not registered, Search and Rescue (SAR) Authorities do not know who you
are, or how to contact anyone who might know anything about your situation (Refer to section 1).
Once the signal (406 MHz) is relayed through the LEOSAR and/or GEOSAR network, SAR forces determine who is
closest, and then track the signal using the 121.5 MHz homing frequency for intermediate and short-range location.
7.2
Satellite Detection
Memory capsule's transmits to the satellite portion of the Cospas-Sarsat System. Cospas-Sarsat is an international
system that uses Russian Federation and United States low altitude, near-polar orbiting satellites (LEOSAR) that
assist in detecting and locating activated 121.5/243 MHz beacons and 406 MHz Satellite beacons.
COSPAS and SARSAT satellites receive distress signals from memory capsule transmitting on the frequency of 406
MHz. The Cospas-Sarsat 406 MHz beacon signal consists of a transmission of non-modulated carriers followed by a
digital message format that provides identification data. The 406 MHz system uses Satellite-borne equipment to
measure and store the Doppler-shifted frequency along with the beacons digital data message and time of
measurement. This information is transmitted in real time to an earth station called the Local User Terminal (LUT),
which may be within the view of the satellite, as well as being stored for later transmission to other LUTs.
The LUT processes the Doppler-shifted signal from the LEOSAR and determines the location of the beacon; then the
LUT relays the position of the distress to a Mission Control Center (MCC) where the distress alert and location
information is immediately forwarded to an appropriate Rescue Coordination Center (RCC). The RCC dispatches
Search and Rescue (SAR) forces.
The addition of the GEOSAR Satellite system greatly improves the reaction time for a SAR event. This satellite system
has no Doppler capabilities at 406 MHz, but will relay the distress alert to any of the LUT stations. When there is GPS
data included in the distress message, SAR authorities instantly know your location to within 110 yards. This speeds
up the reaction time by not having to wait for one of the LEOSAR satellite to pass overhead. Because most of the
search and rescue forces presently are not equipped to home in on the 406 MHz Satellite beacons signal, homing
must be accomplished at 121.5 MHz.
7.3
Global Positioning System (GPS)
The GPS system is a satellite group that enables a GPS receiver to determine its exact position to within 30m
anywhere on Earth. With a minimum of 24 GPS satellites orbiting the Earth at an altitude of approximately 11,000
miles they provide users with accurate information on position, velocity, and time anywhere in the world and in all
weather conditions. The memory capsule stores this data into its distress transmission allowing search and rescue
forces to narrow the search into a very small area and thus minimize the resources required and dramatically
increases the effectiveness of the overall operation.