position to the MRCC, though that may take longer (depending on your
position). At the time of writing, the approximate coverage of the
G EOSAR satellites was as shown in fihTUre 10.2. Even if you are within
that coverage, your EPIRB must not be in shadow (e.g. of terrain) for
the alert to get through.
Note that there is no facility for the MRCC to reply to you using
an EPIRB. You have to trust that the system is doing what it is intended
to do and that help will arrive as a result of your EPIRB alert (see EPIRB
Registration below).Inmarsat EPIRBs
Inmarsat EPIRBs are variously known as:
Inmarsat-E.
L-band EPIRB.- 1·6G Hz EPIRBs.
Regardless of the name used by the manufacturer, they all refer to
the Inmarsat EPIRB. Inmarsat EPIRBs transmit an alert through the
Inmarsat satellites (figure 8.l) - as long as you are in sight of one of those
satellites. The main limitations are:
Within 700N and 700 S. - Not in shadow of terrain/superstructure.
Inmarsat EPIRBs always transmit a position, derived from GPS
or other source. Being geo-stationary, they cannot compute positions
using Doppler or other effect. The G PS-type position is therefore part of
all Inmarsat EPIRBs. Positions from Inmarsat EPIRBs should be in the
RCC within a few minutes of activation, provided that a satellite is in
sight of the EPIRB.
Local homing on 121·5MHz
Both types of satellite EPIRB (Inmarsat and Cospas-Sarsat) usually
incorporate a local homing Signal, with transmission on 121·5MHz (the
civil aeronautical distress frequency). This signal can be picked-up by
direction-finding receivers fitted into SAR aircraft and vessels. Passenger
vessels in the GMDSS and vessels on standby duties at offshore
installations, etc. are usually fitted with a 121·5MHz homing receiver.
EPIRB registration
Every new EPIRB comes with a registration form, for completion
and forwarding to the responsible authority for your vessel's country of188 THE NAUTICAL INSTITUTE