Back in February 2009, the Cospas-Sarsat System which is
a 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, stopped processing
signals from 121.5 MHz and 243 MHz beacons.
Cospas-Sarsat is best known as the system that detects
and locates emergency beacons activated by aircraft,
ships and backcountry hikers in distress. Over the years
many countries have joined the project, either as
providers of ground segments or as user states.
Cospas-Sarsat is based in Montréal, Québec, Canada.
present Cospas-Sarsat only monitors signals from 406 MHz
beacons. The idea was to reduce SAR resources on false
alerts while simultaneously increasing the
responsiveness of the system for real distress cases.
a result “the public interest” the Federal
Communications Commission (FCC) proposed to prohibit the
further certification, manufacture, importation, sale,
or use of 121.5 MHz ELTs. The Commission acknowledged
that aircraft owners and pilots still using 121.5 MHz
ELTs would incur an expense, but concluded that the
safety benefits outweighed the compliance cost,
especially given that the aviation community had been on
notice since 2000 that Cospas-Sarsat would cease
monitoring the frequency.
Prior to the founding of Cospas-Sarsat, the civilian
aviation community had already been using the 121.5 MHz
frequency in the VHF band for distress, while the
military aviation community utilized 243.0 MHz in the
UHF band as the primary distress frequency with
121.5 MHz in the VHF band as the alternate.
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. More recently, the
Cospas-Sarsat system has been designed to detect
only alerts transmitted at 406 MHz. This allows the
system to be optimized for the increasingly
sophisticated 406 MHz beacons, and avoids problems
(including false alerts) from the less-sophisticated
legacy 121.5 MHz and 243.0 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