MH370

Positions and Velocities of Inmarsat-3F1 During the Flight of MH370

7 Comments

Positions and Velocities of Inmarsat-3F1
During the Flight of MH370

Duncan Steel, 2014 March 26.
duncansteel.com

This post contains some further information from me regarding the pinging of MH370 from the Inmarsat-3F1 satellite, intended to assist other investigators.

The following diagram was issued by the Malaysian Government on March 24th, apparently using information from Inmarsat. This appears to render a set of times at which MH370 was pinged via Inmarsat-3F1 which is not in agreement with the times presumed by various other sources (i.e. regular pinging at 11 minutes past the hour).

10155041_740971712614511_1614955617_n

The times read off the above plot are as follows (all UTC):

2014/03/07 16:30:00.000

2014/03/07 16:43:00.000

2014/03/07 16:55:00.000

2014/03/07 17:07:00.000

2014/03/07 18:25:00.000

2014/03/07 18:27:00.000

2014/03/07 18:29:00.000

2014/03/07 19:40:00.000

2014/03/07 20:40:00.000

2014/03/07 21:40:00.000

2014/03/07 22:40:00.000

2014/03/08 00:11:00.000

For each of those twelve times I have used an STK scenario to derive positions and velocities for the Inmarsat-3F1 satellite, and these data are shown in the following twelve graphics, which are screen grabs from my STK scenario. These should be useful to others wanting to look into the positions (connected with analysing the ping time delays) and the velocities (connected with analysing the ping-derived doppler shifts) of the satellite at relevant times during the flight of MH370.

Someone might else might wish to transcribe the data into a machine-readable form. Be my guest!

I hope that the information is self-explanatory. The origin of the Cartesian coordinates (x,y,z) is the centre of the Earth, with the x-axis passing through the Greenwich Meridian, the y-axis being at 90 degrees to this and in the equatorial plane, while the z-axis is perpendicular to the equatorial plane (i.e. a line passing through the poles).

One thing you need to excuse is the fact that the people at Analytical Graphics are labouring under the delusion that a ‘G’ (for Gregorian) is needed after ‘UTC’. Where it says ‘UTCG’ below, it just means UTC. Please forgive them for they know not what they do. But STK is a great tool for this sort of thing.

T1630

T1643

T1655

T1707

T1825

T1827

T1829

T1940

T2040

T2140

T2240

T0011

 

7 thoughts on “Positions and Velocities of Inmarsat-3F1 During the Flight of MH370”

  1. Could any factors say electromagnetic field , disturbance ..invalidate the calculation of the fly path? Thanks

    1. Thanks for the question.

      I don’t think that the factors you mention could affect the flight path, as such, although my expertise/experience is in space science rather than aviation.

      One thing that is connected with what you say that I mention in my posts (e.g. see last post, today) is whether there is significant retardation of the radio signals between aircraft and satellite in the ionosphere. That is, when there is a substantial electron density radio waves are slowed to a speed below the speed of light (just as light itself is slowed as it passes through glass or water: that’s what the ‘refractive index’ represents!)

      Regards,

      Duncan Steel

  2. Thanks for all the analysis. I found your analysis through the TMF site. My question is with the INMARSAT analysis.
    1. I am wondering what the arcs would look like if the initial spike at 18:25 is a sudden altitude drop to 12000 ft?
    2. I am not clear if the INMARSAT analysis take into consideration that 3F1. moving south right after the 18.25, 18.27,18.29 bursts. I am asking since the South Indian Ocean position along the south arc doesn’t seem to make sense while the 3F1 is traveling southward, but it may make sense if the altitude or even depth in sea is dropping. ( my understanding is that increasing of the offset frequency meant away from the satellite based on INMARSAT ) . When did SF1 start traveling south?

    Thank you so much for your help.

    1. Hi Sophia: On (1) I don’t think the arcs are affected greatly by the altitude; remember we are talking about a change in (aircraft) altitude by an amount of order 10 km when the satellite is up near 35,800 km.

      On your point (2) I am also not clear on this and I wish that both the analysis conducted and the raw data (the six ping time delays in particular) were released to the public so that others can check, verify, and so on. It is unconscionable that they have not been. For example, I only started thinking about this overall problem (the satellite pings and their interpretation) whilst on a cycle ride on the afternoon of Saturday 22nd; within 3 hours I had convinced myself that the initial Inmarsat analysis was wrong, and so the chart issued by the Malaysian Government on 15th March was wrong. This was then confirmed by an announcement on March 24th. Meantime the search has been misled.
      If the ping time delays (and the doppler shifts) had been made available for crowdsourced attack by a few people who know what they are doing then a far better set of information would have been available to the search efforts.

      Your specific question of “When did Inmarsat-3F1 start travelling south?” I answered in a post on TMF at March 26, 2014 at 2:50 am. The answer to the nearest minute is 19:36 UTC (on 2014/03/07).

      1. Hi Duncan, thank you for the explanations.

        On #1, yes, I agree with your explanation. Any change in altitude would be well covered in the range of the angles/errors in the calculation.

        On #2, I am increasingly convinced we can’t conclude anything from just the frequency burst offset data. The time delay data is critical. We need the additional circles.

        Sophia

  3. Thanks for the math. With these vectors, is there anyone out there that can back out the s/c Doppler so we can see what the net aircraft Doppler looks like? Based on the combined s/c and aircraft Doppler + system bias (Burst Frequency Offset), and assuming a slow s/c Doppler drift rate (zero speed preflight bias stayed close to 87 Hz), the raw chart data tells us the plane probably moved away from the subsatellite point at ALL Doppler observation times. It was probably moving eastward during the big gap after 01:07, and/or after 02:30.

    Note that the positive “Burst Frequency Offset” numbers >87 Hz correspond to an aircraft moving away from the subsatellite point (assuming slow s/c bias drift) because we know the aircraft was moving away from the subsatellite point immediately after TO.

Comments are closed.