Inmarsat STD-C

Inmarsat STD-C is a data or message-based system used mostly by maritime operators. An Inmarsat C terminal transmits and received on L-Band to various geosynchronous satellites that service each major ocean region (POR, IOR, AOR-E, AOR-W). The information rate is 600 bits/sec. The channel is modulated with BPSK at 1200 bits/sec. The ship-based (or aircraft-based) Inmarsat C terminal is called an MES (Mobile Earth Station) while the land based ground stations are called LES (Land Earth Station).

In the Pacific Ocean Region (POR) there are nine different LESs which the following IDs and Frequencies.

201 1539.655 Telenor Satellite Services Inc
202 1539.625 Stratos Global New Zealand Auckland
203 1539.515 KDDI Yamaguchi Japan
204 1539.595 EIK Telenor Norway
210 1539.605 Sentosa Singapore
211 1539.665 Beijing MCN China
212 1539.505 Stratos Burum Netherlands
217 1539.635 Nudol Morsviasputnik Russia
221 1539.615 France Telecom MSC

There is a main Network Coordination Station (NCS) that assigned signaling channels (used to uplink) to the MESs.

The main NCS frequency for POR is 1541.450 MHz.

The NCS channel is also where you will receive Enhanced Group Call (EGC) messages. There are two types of EGCs, SafetyNET and FleetNET; SafetyNET is used for anything related to safety, such as SAR, navigation, coast guard, etc. FleetNET is typically used for distribution of news, weather, incidents, etc.

There is also various data services such as 2-way messaging, email, polling, position reporting and distress alerting.

Here is an example EGC Navarea message:

NAVAREA XI WARNING
NAVAREA XI 0706/13
SOUTH CHINA SEA, SOUTHERN PART.
PIRATES INFORMATION.
231415Z SEP. 04-52N 104-05E.
EIGHT PIRATES WEARING MASKS ARMED WITH A
HAND GUN AND LONG KNIVES IN A HIGH SPEED
CRAFT APPROACHED AND BOARDED AN OFFSHORE
TUG UNDERWAY. THEY TOOK HOSTAGE ALL CREW
MEMBERS, TIED THEM UP AND STOLE THEIR
PERSONAL BELONGINGS. AFTER ABOUT THREE
HOURS, THE PIRATES LEFT THE VESSEL. CREW
MANAGED TO FREE THEMSELVES AND THE
MASTER REPORTED THE INCIDENT TO THE
OWNERS. VESSEL RETURNED TO THE PORT OF
DEPARTURE WHERE THE AUTHORITIES BOARDED
THE VESSEL FOR INVESTIGATION. MASTER
REPORTS A POSSIBILITY OF A MOTHER VESSEL
IN THE VICINITY.
VESSELS REQUESTED TO BE CAUTION ADVISED.

Here is an example EGC Distress Alert:

Eik LES 2-OCT-2013 22:25:07 676140
SUBJECT: **406 MHZ DISTRESS ALERT**
MESSAGE: AT 022143 UTC OCT 13,
A 406 MHZ DISTRESS BEACON HAS BEEN DETECTED IN
POSITION 27-37N 139-57.8W.
NO FUTHER INFORMATION HAS BEEN GIVEN WITH THIS ALERT.
VESSELS IN THE AREA ARE REQUESTED TO KEEP A SHARP LOOKOUT,
ASSIST IF POSSIBLE AND REPORT SIGHTINGS TO RCC HONOLULU, HI.
VOICE 808-535-3333,
FAX 808-535-3338;
TELEX 392401 ANSWERBACK CG14 UD;
MF/HF DSC 003669993 OR 003669990
EMAIL: JRCCHONOLULU@USCG.MIL

Here is an example of email in response to SSAS ALERT test message.
Email addresses and confidential information have been removed.

From: operations.sin@xxxx.com
Date: 10/02/2013 06:23:49 AM
Subject: SSAS ALERT REPORT
Good day Capt,

Well received your SSAS test alert message.

Thanks
xxxxxx/Ops

—–Original Message—–
From: xxxxxxxx@xx.xxxxx.com.sg
Sent: Wednesday, October 02, 2013 2:22 pm
To: Operations Singapore
Subject: SSAS ALERT REPORT
Importance: High

To+xxxxxxxx@xxxxx.com
Subject+SSAS ALERT REPORT

!!!! Test Call !!!!
— SSAS ALERT MESSAGE —
Vessel Name: SMIT SERAYA
MMSI: 566xxx000
IMN: 456xxx410
IMO:9662xxx CALL SIGN:9V9845
Ship Security Alarm,Please Help!!!
LAT: 01:18.24N
LON: 103:40.16E
Time: 10/02/2013 06:13:12(UTC)
COURSE: 307 deg
SPEED: 00 kt
Time: 10/02/2013 06:13:11(UTC)

SEN Ref#540848 sent on 2-OCT-13 06:14

The test message shown above is from a ship called the Smit Seraya. Here is a picture the actual ship.

Smit Seraya

Smit Seraya


Based on the Latitude and Longitude in the Test Call above, here is the location of the ship when the test message was sent.
Location of Smit Seraya for SSAS Alert

Location of Smit Seraya for SSAS Alert

Category(s): Inmarsat
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3 Responses to Inmarsat STD-C

  1. Can some one guide me regarding the standard document for Inmarsat-C messages for IOR or some material for Inmarsat-C , L band messages decoding

    • Inmarsat specifications are proprietary. You have to empirically decode the messages. There a few old documents running around the internet that give some hints on things (you can search for these as easily as anyone). But 90% of the work is just looking at bits and thinking…

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