OK one more hypothesis, but there are so many!

The communication Company SITA continued tracking MH370′s transponder flying northeast until 17:27 UTC. At 17:24 UTC MH370 was located at 006.93′N, 103.59′E. The distance from that location back to the west coast of Penang is 250nm.

Has anyone ever bothered to consider how long it would take to fly this distance?

Flying at 35,000ft and 471kt the last recorded airspeed, MH370 would have required 32 minutes to reach the location west of Penang, far more than “nearly 20 minutes.”

If as Malaysia tells us MH370 descended to 5,000ft to evade radar then airspeed would have been limited to just 250kt. The time required to fly 250nm back to Penang would then have required an hour.

Even flying at 35,000ft MH370 could not have reached Penang in nearly 20 minutes. At 35,000ft it would have been spotted by military radar at Kuantan, but it wasn’t …. because MH370 never flew west.

Regarding timing, you are correct. It is simply impossible to calculate an accurate distance without having an accurate timing base. If all of the components in the ‘system’ had a GPS receiver an accurate time base would be available. However, the system would had to have been designed to use that information. I seriously doubt that it was. The Inmarsat satellite was launched in April of 1996. That probably means the satellite’s technology dates from 1995 or before. So what does that mean? How accurate is that satellite’s time base?

Duncan Steel has a very interesting blog here:
http://www.duncansteel.com/archives/419

Check it out.
regards,
Bob

I have no expertise in this and have been unable to find a solution online. Any technical information would be greatly appreciated. Thank you.

The Excel? graph from Inmarsat shows that the pings were not always hourly. So the first question about SQ68 should be whether it had the same ping schedule as MH370. Those chances, in my mind, are low. Once the schedules are different, the wobble would mean different dopplers.

The assumption by Jeff Wise about the 2:11 ping radius, I believe, is not solid. He quoted Inmarsat as saying the “timings got longer.” It’s not clear whether this is referring to a time shift or a frequency shift. Consider that a later ping could be closer to the subsatellite position, yet receding from it. Correct me if I’m wrong, please, but this could easily allow the plane to have been a bit closer to the subsatellite position, supporting either Keith’s route OR the avoidance-of-Indonesia route.

The real issue here is that we need ping times, frequencies, and distances. It looks like the satellite location is known to y’all, which is huge.

My response is, ‘sure, why not?’ It all depends on what these ‘pings’ we’re all discussing actually are. Remember, these are essentially registration queries. The ‘system’ sends out a request asking if a station is active. The sleeping station wakens and sends a message back to ‘the system.’ These are the ‘pings.’ First question,

1. How many responses does the AES send? Does it receive the request and send one response? Two responses? More?

Let’s assume that two or three are sent. These are very short bursts that probably do not, in aggregate, take one second. If I have this upside down will someone please correct me?

Let’s recast Keith’s question to something like, “If two aircraft are flying in close proximity along the same or similar range arcs could one aircraft demonstrate doppler data different from the other for a period of one or two data bursts every hour?” My response is ‘why not?’ Especially if one of the aircraft is making occasional course/speed corrections to stay at some predetermined position relative to the other.

Regardless of these arcs’ accuracy the aircraft are, by definition, on that arc (actually a band). And, if one of the aircraft jogs (relatively) towards or away from the satellite the receiver will see a doppler shift. Remember, the doppler shift is only telling you that the aircraft is moving radially towards or away from the satellite – not whether the aircraft is in the northern or southern hemisphere. To my mind this is slicing the baloney pretty thin.

Remember also that this is all occurring in the space of a second or less. The ‘system’ receives a ping or pings that are used to determine a radial distance to the aircraft and is also, by the way, able to discriminate a doppler shift that rules out either the northern or southern hemisphere. I’m sorry, I’m having a problem with this. This is not analogous to a constant track provided by a dedicated or ad hoc tracking system. Second question:

2. What magnitude of radial velocities are Inmarsat reporting? Could these velocities also be explained by an apparent velocity change caused by an impulse?

To further answer Keith’s question… What is the probability that either of these (southern vs. northern) solutions is correct? Probably about fifty-fifty. Especially with the dearth of real information we’re stuck with.

Publish the raw data and give us all a chance to chew on it.

regards,

Bob

You were correct about the first Inmarsat analysis (the graphic released by the Malaysian government on 15 March showed 3F1 on the Equator), but in the latest analysis, which showed the aircraft must have flown south, not north, Inmarsat did take the changing position of the satellite into account. Apparently that was part of the reason why they were able to conclude the plane flew south, not north. Below is a quote from the following newspaper article by the Daily Telegraph (UK) on 24 March:

http://www.telegraph.co.uk/news/worldnews/asia/malaysia/10720009/MH370-Britain-finds-itself-at-centre-of-blame-game-over-crucial-delays.html

“On March 19, Malaysia Airlines told SITA to use the AAIB as the main analyst of the Inmarsat data. The AAIB, part of the Department for Transport, passed on its own interpretation to Malaysia, but it was not until Sunday, March 23 that a further calculation by Inmarsat convinced the Malaysians of the aircraft’s whereabouts.

Analysts realised that their calculations had not taken into account the geostationary satellite’s very slight movements in relation to the earth. Once that was factored in, the northern corridor was ruled out completely. The calculations were sent off to be checked over the weekend before being passed to Malaysia on Sunday.”

Thanks for the sanity check. Serves me right for trying to work out the meaning of an equation without taking the time to understand the terms (before running off to another meeting)

You are right, the velocity of the wave front is the speed of light, not the velocity of the aircraft. I am happy to note that my instincts are still reasonably good since I thought the result I got could not be correct. I can’t remember where I read it but I understood that Inmarsat measurement accuracy for frequency was on the order of nanoseconds so a 1.5kHz shift would be easily detectable if any additional error introduced was reasonably small.

Duncan Steel – sorry about the inadvertent name change. I used your data with a fair amount of “artistic license” to perform an order of magnitude analysis. I just looked at the lat and long points you posted with the times and the distance that would represent them assumed a max speed at midpoint. From an order of magnitude perspective, 10 kph vs 50 kph is not that large.

I too took a land survey course way back when and my favorite expression that described the discipline was ‘measure with a micrometer, mark with chalk, cut with an axe’ – right or wrong, I try to avoid measuring with a micrometer for a first sanity check.