Time:1559:57 UTC

Time:1559:57 UTC

0. Event Time and Type

Event Time:  23:59:57 MYT   Edit.

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Event Type: satcom default   Edit.

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1. Summary ..................................................................................................Edit

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The SATCOM initiates a Log-On handover as Class 3 (voice and data capable) to the IOR I-3 satellite, using the HGA subsystem, with a valid Flight ID. This suggests that the IOR is now considered to be the best available satellite. This is probably because either the line of sight to the IOR satellite is now clearer than that to the POR satellite, or the antenna gain in the direction of the IOR satellite has become higher than the antenna gain in the direction of the POR satellite.

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2. Details .......................................................................................................Edit

1. Safety Investigation Report MH370/01/2018 Satellite Ground Station Logs - Key Observations

   The SATCOM initiates a Log-On handover as Class 3 (voice and data capable) to the IOR I-3 satellite, using the HGA subsystem, with a valid Flight ID. This suggests that the IOR is now considered to be the best available satellite. This is probably because either the line of sight to the IOR satellite is now clearer than that to the POR satellite, or the antenna gain in the direction of the IOR satellite has become higher than the antenna gain in the direction of the POR satellite.

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3. Notes .........................................................................................................Edit

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References for events at or about the time of 2359:57 MYT, 7 March 2014 (1559:57 UTC, 7 March 2014).

The source document is cited first (with a link to the full text), followed by one or more relevant extracts.

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Pre-Flight

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Narrative

<section begin=Narrative />

23:59:57 MYT, 7 March 2014

Satellite Data Unit: Log-On Handover

The SDU initiated a Log-On handover as Class 3 (voice and data capable) to the Inmarsat GES via the IOR I-3 satellite, using the HGA subsystem, with a valid Flight ID. The Data Communication Logs (updated version), released to the public by the DCA (Malaysia) and Inmarsat, starts with this event. Information about this event is summarised in the table below.

Source	Satellite Data Unit on aircraft 9M-MRO
Destination	Inmarsat Ground Earth Station (GES) near Perth in Western Australia
Message	Log-On Request Class 3 - Voice and Data (Log-On Handover from the Pacific Ocean Region to the Indian Ocean Region)
Satellite	IOR I-3
Antenna	High Gain Antenna subsystem
Flight ID	MH0370
Burst Frequency Offset (BFO)	99 Hz
Burst Timing Offset (BTO)	19380 microseconds

<section end=Narrative />

References

Item 1

1600 UTC, 7 March 2014 (1559:57 UTC, 07 March 2014)

Factual Information MH370/01/15/1.9.5.3

1.9.5.3 SATCOM Ground Station Logs of the Event - Summary

In the summary below, times are truncated to the nearest minute (the format is Hours:Minutes) and in Section 1.9.5.4, times are truncated to the nearest second (the format is Hours Minutes:Seconds).

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1. Prior to take-off, the SATCOM Logged On (normally) a number of times, the last time being at 16:00, when it sent a valid Flight ID to the GES. The SATCOM link was available for both voice and data (known as Log-On Class 3).

Item 2

Factual Information (2015) 1.9.5.4

1.9.5.4 SATCOM Ground Station Logs - Key Observations in Chronological Order

4. 1559:57 - The SATCOM initiates a Log-On handover as Class 3 (voice and data capable) to the IOR I-3 satellite, using the HGA subsystem, with a valid Flight ID.

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Notes

1. The time of the last logon by the SDU prior to take-off, 1559:57 UTC is rounded to 1600 UTC.
2. This event indicates that a member of the Flight Crew changed the operating channel for the Satellite Data Unit so that it would establish a connection through Inmarsat's Indian Ocean Region satellite. (Each region uses different frequencies or channels).
3. Following the change, the configuration would be suitable for the flight - using the satellite over the Indian Ocean Region, correct Flight ID and correct Aircraft Number; and Voice and Data capable.
4. The first release of the Data Communication Logs, provided by Inmarsat and released by the DCA (Malaysia), did not include this event.

5. An updated version of the Data Communication Logs was released in December 2014, including data for this event. The following explanation was provided at that time:-

   "Requests have been received from external interested parties to release any information from the SU logs (recorded at the ground earth station for the communications with the terminal on 9M-MRO) containing BTO and BFO values prior to those originally published. There are two logs that contain BTO and BFO data prior to 1600 UTC while 9M-MRO was powered-up at the gate in Kuala Lumpur. The two additional log messages have been incorporated into the first two lines of the table below. As the two message are from Channel R600, a 4,600 microseconds calibration needs to be subtracted (19380 – 4600 = 14780) when comparing with subsequent R1200 messages. This is the same as applied for the messages at 18:25:27 and 00:19:29. The remainder of this document is as previously released by Malaysia in May 2014."

6. The actual time of the Log-On Request(s) in the Log was 15:59:55.413 and 15:59:56.413 (which is rounded up to 1559:57 UTC) and related transmissions continued through 1600 UTC.
7. Data for SATCOM transmissions prior to this event was not included in the Logs because they used the satellite over the Pacific Ocean Region.

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Coordinated Universal Time

Malaysian Time (MYT) is Coordinated Universal Time (UTC) + 8 hours

Satellite Communications

Inmarsat geostationary satellite above the Indian Ocean

HGAs

High Gain Antenna(s)

Flight Identifier, for example MH370

Indian Oceanic Region

Pacific Ocean Region

Satellite Data Unit

Ground earth station. A satellite ground station sends or receives data from orbiting satellites. (Source: ATSB)

Department of Civil Aviation (Malaysia)

Aircraft Registration Number for the Boeing 777 used for Flight MH370. More Info

Flight ID MH370

Burst frequency offset. BFO is a measure of the difference between the expected frequency of a satellite transmission and the frequency received at the ground station. (Source: ATSB)

Burst Timing Offset. BTO is a measure of the time taken for a satellite transmission round trip (ground station to satellite to aircraft and back) and allows a calculation of the distance between the satellite and the aircraft. (Source: ATSB)