For our French readers, here is an article published in Astronomy and Space (Ciel & espace) about the search for MH370.
Grâce aux satellites on sait où chercher le Boeing MH370 de Malaysia Airlines disparu en 2014. Une nouvelle exploitation de données satellites a permis de déterminer où s’est vraisemblablement écrasé le vol MH370. Ce Boeing 777 de Malaysia Airlines a disparu dans l’océan Indien le 8 mars 2014 dans des circonstances qui restent mystérieuses.
You can view the article here
Vous pouvez lire ici
Il est intéressant qu’une publication “scientifique” comme Ciel & Espace publie cet article : je pense que c’est le premier qui émane d’une telle source, entre publication scientifique “pure” et presse grand public.
Et il est réconfortant que l’article s’articule autour d’une publication des membres de l’Independent Group qui est lui aussi “entre deux domaines”, celui des journalistes et des amateurs sérieux (que je n’hésite pas à mettre dans le même panier…), et celui des membres officiels des différents organismes qui ont participé directement aux recherches.
L’article lui-même est fort intéressant, mettant en exergue certains faits qui ont pu passer inaperçus dans les milliers de lignes écrites à propos de cette disparition comme, par exemple, la signification des débris retrouvés et celle de leur nombre.
Personnellement, le seul reproche que je pourrais faire, est l’utilisation de statistiques pour un évènement unique, mais je suis nul en “stats” et j’ai donc une bien naturelle tendance à m’en méfier…
Merci, en tout cas à Richard d’avoir, je présume, poussé à cette publication et surtout d’avoir créé ce site, même si c’est peut-être par réaction (ceux qui “suivent” l’IG me comprendront). Non seulement je comprends cette réaction, mais que je l’approuve à 100%.
Et quelques commentaires et publications en français ne peuvent que contribuer à garder vivante la recherche de cet avion : MERCI !
PL
Hi. Great work. What uncertainty and error analysis has been done on all the analysis? Example do Inmarsat signals bend between space and earth like light?
@joseph robert flack,
Welcome to the blog!
You ask: “What uncertainty and error analysis has been done on all the analysis? Example do Inmarsat signals bend between space and earth like light?”
9M-MRO the aircraft used for the flight MH370 was equipped with the Inmarsat Classic Aero system, which has been in operation since 1990. The aircraft satellite communication system operates at L-Band, transmitting signals to the satellite at 1.6 GHz and receiving signals from the satellite at 1.5 GHz. The ground station in Perth, Australia to satellite link uses the C-Band, transmitting at 6 GHz and receiving at 4 GHz. The particular satellite where MH370 was logged on was 3-F1 above the Indian Ocean near the Equator at 64.5°E, but this sub-satellite point moved its location during the flight of MH370:
https://www.dropbox.com/s/ze28269kihut3o7/Inmarsat%203F1%20Sub-Satellite%20Point.png?dl=0
Most communications satellites are in geostationary orbit at around 35,900 km above the equator, so that the satellite appears stationary at the same point in the sky. The satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. The radio waves used for satellite links travel by line of sight. The rays or waves may be diffracted, refracted, reflected, or absorbed by the earth’s atmosphere but the large dish antennas used ensure a good signal to noise ratio.
I use the Earth-Centered, Earth-Fixed coordinate system (ECEF). Between the time when MH370 took off on 7th March 2014 at 16:41:53 UTC and crashed on 8th March 2014 at 00:20:24 UTC, the Inmarsat satellite changed position. The minimum distance from the centre of the Earth was 42,171.848 km and the maximum distance was 42,187.646 km. The satellite also changed speed in the MH370 timeframe. The minimum velocity in relation to the centre of the Earth was 0.002107 km/sec at 19:36:09 UTC. The maximum velocity was 0.83287 km/sec at 00:20:24 UTC. There was even an eclipse of the satellite during the MH370 time frame.
You also have to keep in mind that the Earth is not a perfect sphere. I use the WGS84 model of the Earth, so for example the Earth’s radius at the Perth ground station is 6,384.075 km.
Chris Ashton, Alan Shuster Bruce, Gary Colledge and Mark Dickinson of Inmarsat describe how the system operates in their paper titled “The Search for MH370” dated 4th September 2014:
https://www.dropbox.com/s/tprui5tp235efmm/Inmarsat%20Paper%20Sept%204.pdf?dl=0
The Inmarsat satellite is ageing and position keeping is difficult. The inclination was steadily increasing in 2014 during the MH370 flight, but all these factors have been taken into account in determining the satellite ephemeris on 7th March 2014 and using the BTO and BFO satellite data in relation to the MH370 flight path analysis and the subsequent uncertainty and error analysis:
https://www.dropbox.com/s/92keojxlm0i07vi/Inmarsat%203-F1%20Inclination.png?dl=0
There have been a number of analyses of the accuracy and precision of the Inmarsat satellite data. We will be including an analysis of the accuracy of the WSPRnet data in the upcoming technical paper.
However, the accuracy overall so far using WSPR signals over a mean distance from the transmitter to the aircraft of 11,542 km is a delta azimuth of 0.01001581° and is very good at ± 2.018 km. This is better than the Inmarsat BTO satellite accuracy which ± 3.6563 km along the earth’s surface at the 7th Arc or ± 31.35 µs (± 4.7 km) between aircraft and satellite.