Orolia GSG-5 Series, User Manual With Scpi Manual, Page: 202 / 392

Argument of Perigee(rad): 1.117132574
Mean Anom(rad): –3.089600
Af0(s): 1.7600243882E-04
Af1(s/s): 1.3415046851E-11
week: 755
5.8 RLS (Return Link Service)
As part of the Cospas-Sarsat System, Galileo satellites are capable of picking up emer-
gency signals emitted on 406 MHz by distress beacons, and transmitting a signal back to
the beacon via the E1 frequency to confirm receipt of the distress signal. This technology
has been developed under the international Cospas- Sarsat program. It comprises the
Galileo-enabled distress beacons, the SAR payload on the Galileo satellites, as well as
ground-based receiving stations (LUTs) and Mission Control Centers.
If the option "Galileo" (Opt-GAL) is installed, GSG is capable of simulating the Return Link
Message (RLM) transmitted by the Galileo signal to the distress beacon.
As a user you interact with the GSG by inputting the RLM parameters as a SCPI command
into the computer; GSG will then take this message and simulate its transmission on the E1
frequency from the satellite to the distress beacon.
For more information on SCPI command syntax, and examples, see "SOURce:SCENari-
o:RLM" on page 300 .
5.8.1 SAR Data
Each Return Link Message encapsulated in an SAR data page contains the following data:
Beacon ID (60 bits): This field is used by the beacon to discern whether the RLM
received is, indeed, addressed to itself or to some other beacon.
Message code (4 bits): Defines the message type.
Parameters field (16 bits for the short RLM, 96 bits for the long RLM). This field
provides the information that SAR operators wish to send to the Galileo-equipped
beacon.
Short RLMs are used to provide the activated Galileo-equipped beacon with a short
acknowledgement of various kinds of commands (e.g., to reduce its transmission rate).
Long RLMs are intended for more complex commands in which several parameters may
be required (e.g., to contain operational information or the coordinates of a location).
For more information on SCPI command syntax and examples, see "SOURce:SCENari-
o:RLM" on page 300 .
186 User Manual GSG-5/6 Series Rev. 27
5.8 RLS (Return Link Service)