I see some considerations about Ground Earth Station in recent posts. In the published "raw data", there is this "remark":
"16:41 - Take-Off.Logged-On to Ground Earth Station (GES) 305/301, via the Indian Ocean Region (IOR) Inmarsat I-3 satellite"
And, the title line of each page shows that the GES numbers are octal.
There are only 4 lines with the code 301 on the main data pages (at 18:39:52,907), 2 in Appendix A (at 18:39:58,407 and 18:40:55,407) and none in Appendix B.
305 (197 decimal) is Perth and 301 (193 decimal) is Eik (in Norway) from the page 21 of this doc:
http://esupport.thrane.com/index.php...oaditemid=1411 (found reading Reddt post GES ID (octal) 305, what is 301? : MH370).
A note on the same page indicates that only Perth and Eik support the "Aero 1" services, but the document is from 2002.

About the (virtual) "nominal terminal": I don't understand why to use a virtual terminal which will ask for theoretical computation. I would understand the use of a physical one which could continuously give a "balance duration" by sending back some signal. Is it technically possible that a "special" signal from the GES is regularly sent and its very faint echo from the Earth surface (sea for instance!) below the satellite is detected and used? And by difference gives the BTO value?

Why the first "publications" from Inmarsat about the "pings" were angles? In the first days after, some people had thought those angles were from signal strength or from antenna number: this happens to be false (strength gives a too low accuracy, and 3F1 is not a multi-beam satellite). We know now that these arcs come from a duration. So, why to convert this value in angles rather than in distances?
If the BTO is computed like guessed above, the simplest geometry using the true distance of the satellite from the Earth center and the Earth radius gives an angle (from the arccosine of the relation between the sides of a triangle).

I'm pretty sure Eik was decommissioned last year, and the 301 GES is now in Perth.

My understanding is that 305 is Perth, W.A., and 301 was Eik, Norway, but is now Burum, near Groningen, Nederlands.

EDIT:: The following Inmarsat Aviation Safety Services -2013 Update PDF file outlines the current Aero setup.

I believe they were looking for the easiest media means of explaining the Doppler, as opposed to the "brain teaser" the BTO 'nominal terminal' is.:cool:

Surely this was simply an attempt to make an 'easy' visualisation of the calculated range of the aircraft as an earth projection based on signal 'round-trip time' and had nothing to do with Doppler which I do not think had been looked at at the time by Inmarsat? It certainly did cause some confusion as to the satellite aerial technology.

BOAC, MM43

I think BOAC is right. The elevation angles correspond to the ranges. In the Inmarsat promotional materials they show elevation angles across the geographical footprints of their antennae. I suspect that internally Inmarsat use elevation as a proxy (shorthand) for range from the subsatellite point. From the point of view of radio reception elevation is the key parameter.

Some questions for the experts here. (I have looked at Richard's thorough paper):

1) Given that Inmarsat have produced a 'best fit' route for the aircraft, is this available to us? (It is a given that it will no doubt be a 'wide corridor' and not a precise track)

2) If so, can it be established what the approximate true and magnetic tracks were throughout the supposed southern flight? What is the projected path of a continued track as flown, ie is it possible to have guess at any waypoint that may have been active or be more certain that a fixed magnetic heading was in effect?

Not the Inmarsat version of course (no detail has been released), but I can derive the numbers from my model.

Others will have to speak about waypoints. Here is the data for the track from my model to the Inmarsat hotspot. As I said earlier, the track to the Inmarsat hot-spot is the best fit course from my modelling using all 4 BFO values, and a maximum speed of 500kt for the first leg as a limitation. If the allowed maximum speed on the first leg is higher, there are tracks to the South that fit better.

Interestingly, that model track has a quite smooth change of true heading of 14degrees per hour. Not all the tracks in the model set have that property.

The track data
https://www.dropbox.com/s/6jdz1srdc0...t_hot-spot.xls

and the track itself.
https://www.dropbox.com/s/8cfreiw89e...t_hot-spot.jpg

- further to my PM, earth rate is 15 degrees per hour...................

Last night's Horizon seemed well balanced ...no embarrassing claims about hijacks , crew mutiny , etc etc.

Nice to see Inmarsat explain their reasons for search locations , although still not convincing.

AAIBs man spoke with the voice of reason.....no theatrics.

When they go back to the right place , they might find the wreckage , but that depends on those in the know coming out of the woodwork.

I thought that the 2 guys from Inmarsat were very honest in their explanations, although I admit I would like to have seen the chinagraph images the correct way round.

What more would you like to have for their conclusions to be convincing? Are you referring to the blog post here:

TMF Associates MSS blog » MH370: analysis of where to look?

that gives another set of points that seem to be further south west of the Inmarsat estimate? It may be that Inmarsat used different values for the winds aloft, or indeed this group of analysts have used incorrect values from alternative sources. I don't know if there is any really solid wind information for the area in question but added to the IAS uncertainty (has this been resolved?) it might be responsible for these differences.

Inertial navigation failure, causing a drift in the platform? Perhaps we are drifting away from the ping data which is the subject of this thread. The ping data however interpreted shows the path that was followed. The reasons for that path are a different discussion.

I'm not sure what you mean. They've said several times that satellite motion is the primary source of doppler in the signal because the aircraft attempts to correct for its own motion, but not satellite motion.

If the aircraft wasn't correcting for its motion, we'd have had a much better idea of where it went a long time ago (and, if it was correcting for satellite motion, we'd probably still be arguing about whether it went north or south).

The search is heading SW, towards the Inmarsat hotspot, apparently.

MH370: Australia to search seafloor of Indian Ocean for missing Malaysian jet - The Economic Times

Wow, nice paper ! :D Can't help thinking your wife is a bit right :8
Interesting piece of information about the D3 meaning / compensation.
You did not try to model accurately the 1st part of the trajectory and we have no handshakes between 17:10 and 18:30, ok with that, but the trajectories you used frankly cross the Indonesian airspace: shouldn't such trajectories have prompted a reaction from the Indonesian AF as they did in the past ? I think it is possible to reproduce the 3rd of the 3 handshakes at around 18:30: can you visualize the continous underlying time serie D1_aircraft+D2_aircraft ? (not simply its values at the handshake instants).

Yes and no. The hotspot is a much larger area showed before as a rectangle, the area searched so far is in its extreme north-east corner. Using the word 'hotspot" is misleading because it suggests a small "hot" spot but in fact this is a very large area.

Inmarsat vehemently objects to this new area being called a "hotspot", they say it is a pretty large area and the search will be difficult. It may very well be the same area depicted on earlier maps since Inmarsat in this interview says all the relevant calculations were performed within 2-3 weeks of the loss. They also defend actions of the search teams which concentrated on a tiny northern sliver of the area where the pings were believed to be coming from.

Inmarsat: 'No hotspot' in search for Flight MH370 | Asia | DW.DE | 18.06.2014

I was trying to use the simplest possible model that will satisfy the data to the level of error in that data, which I estimate to be ~2Hz, one sigma. So I have used two parameters only, the speed of the first leg and the speed of the rest of the legs. As noted in section 7.9, the speeds of the first and second legs can be traded to move the position of the 18:29UT ping North, without affecting the fit. We are on very dodgy statistical ground here. There are only 4 reliable BFO data points at most, and I am fitting two parameters already. If I fit more parameters there is a danger of 'over-fitting', which means any data can be fitted. What the fitting process must avoid (of course the investigation knows this) is to avoid just joining the data dots with a complex model. Such a solution would definitely not be correct, there is noise in the data and this has to addressed.

I have been concerned that presentations (to the families) have made attempts to bend the path round Indonesia. The ping rings in the slides shown were not those derived from the data log (or from the slide of satellite elevations). The precisely defined 18:29UT turning point in the slides seems to be an assumption about the navigation process of the flight - perhaps correct, but not supported by any fact of which I am aware.

Better in the BFO/BTO analysis to avoid using data that cannot be 100% verified. If the data is consistent with the radar data, a consistent track should appear as a statistical acceptable solution.

Yes, I think a course can be generated that will satisfy some of the data around ~18:29UT, but I am not sure it adds any weight to the fit, that is a degree of freedom has to be used up matching the added data point.

On the time data series I will work on that. It will require an assumption about how the course changes between ping-rings (as a function of time) - at the moment I have just modelled one course per leg. That can be done of course, but it is another assumption.

I will include that in a full run. Effectively that is what I did in section 7.9 of the paper but didn't include much detail. It will need a different average speed from 18:29UT to 19:41UT, but that may be consistent with potential scenarios for the flight. I was trying to keep the model simple, as I said.

I wasn't overwhelmed by the ATSB fact sheet when it was released. The scale is small, but the ping-ring map seems to show the same wrong data as the Malaysian presentations, and there is speculation about possible navigation waypoints on the route. It wasn't clear what level in the investigation it had come from.

I had missed the fact that the small search area was due to signals picked uo by HMS Echo.


Regarding this larger area that Inmarsat have calculated, can someone confirm my understand below is correct.

A) Some time back there was a diagram showing three segments of the southern arc based on the finalpartialping , if i recall they were called something like the northern section, the middle section and the southern section, and calculations favoured the northern section, which was when they moved from the south of Perth way up north.

B) This section then has to be extended south eastward (approx flight path) to account for the final glide and that is the area they will be searching first. It is also the last area they searched for debris (presumably shifted somewhat to allow for ocean currents/time lapse).

Is that correct.