Black Boxes detection
 

Hi there
Thales and the French Marine would have isolated (location accuracy: a few tens of km²) the pinger signals embedded in sonar signals collected by the Emeraude during the 1st phase of searches. According to these new data, the BEA is currently reallocating its search means approximately 2 hours of navigation (~50 km ?) to the south of the area being explored just before (to the north west of the last known ACAR position):
Communiqué de presse, 6 mai 2010
http://www.bea.aero/fr/enquetes/vol....4052010.fr.jpg
Would it put the new search zone in right part of the area 1 ? (wonder how it compares relatively to the back drifted crash areas with a large turn to the west like:
http://www.pprune.org/5118143-post4200.html, from an initial work by mm43)
A new press release is scheduled for next monday at the BEA in Paris, hopefully more will be said about this new search zone, and the certainty that can be allowed to the signal identification. The Navy already warned that this may be a tremendous task given the seabed roughtness.
Jeff

I'm sure MM43 will be along shortly. In the meantime here are the Seabed Worker's satellite-recorded positions between 2 May and 07:02z today. Apologies for the lack of spacing between fields; the data is taken straight from an Excel spreadsheet.

GMT Local Course Speed Latitude Longitude
06-May-2010 10:02 06-05-2010 07:02 239.7 0.5 3°15'11''N 31°10'47''W
06 May 2010 01:04 05-05-2010 22:04 24.9 2.2 3°18'22''N 31°08'01''W
05 May 2010 23:21 05-05-2010 20:21 218.6 1.1 3°17'04''N 31°08'07''W
05 May 2010 21:45 05-05-2010 18:45 202.7 0.6 3°16'46''N 31°08'10''W
05 May 2010 12:46 05-05-2010 09:46 145.8 0.3 3°16'59''N 31°08'06''W
05 May 2010 11:10 05-05-2010 08:10 261.9 0.4 3°16'57''N 31°08'05''W
05 May 2010 00:32 04-05-2010 21:32 65.3 0.8 3°15'56''N 31°10'37''W
04 May 2010 22:52 04-05-2010 19:52 224.8 0.6 3°16'15''N 31°10'15''W
04 May 2010 12:14 04-05-2010 09:14 265.5 0.6 3°15'57''N 31°08'30''W
04 May 2010 10:36 04-05-2010 07:36 346.8 10.4 3°06'44''N 31°06'26''W
04 May 2010 01:46 03-05-2010 22:46 294.4 0.8 3°17'12''N 31°08'07''W
04 May 2010 00:00 03-05-2010 21:00 273.4 1.1 3°17'14''N 31°08'19''W
03 May 2010 22:24 03-05-2010 19:24 215.9 0.4 3°17'08''N 31°08'00''W
03 May 2010 13:56 03-05-2010 10:56 64.9 2.3 3°17'07''N 31°08'04''W
03 May 2010 11:46 03-05-2010 08:46 107.2 10.3 3°17'33''N 31°08'05''W
03 May 2010 01:19 02-05-2010 22:19 13.0 9.6 2°15'07''N 31°28'01''W
02 May 2010 23:28 02-05-2010 20:28 17.2 10.1 1°57'37''N 31°33'06''W
02 May 2010 14:44 02-05-2010 11:44 16.0 11.7 0°26'38''N 32°00'10''W
02 May 2010 12:55 02-05-2010 09:55 16.3 11.6 0°06'22''N 32°06'04''W

so they never delayed any further searches untill the results from phase one had been analysed, there must be some logic there somewhere but im dammed if i can see it and as for saying they know the whereabouts of the boxes i think pretty much everybody knew they where in the sea,
good effort, how much did that gem cost, is there a greek finance minister running this search?


gs

Good Spark,

As for logic, perhaps one should assume that there was never any certainty the tapes would reveal anything new, despite all the work on them.

Two new satellite position reports show the Seabed Worker at approximately the same position as the latest one in my earlier post.

Good Spark;
BEA was informed this morning of the Navy's results. My understanding is that there is no contact with the AUV's until they surface after completing their programmed mission, which can be up to 24 hrs after being sent down. Perhaps that explains the Seabed Worker's positions. French press reports put the cost of the current and earlier search efforts at 28 million euros (BEA 10m; AB&AF 13m; french navy 5 à 6 m).
HN39

Hi,

This new research zone is about 40 Km south of the last (supposed) know position of the AF447.
That's very interesting ..
Can we dare supposing the AF447 take purposely a back (or altered) course for avoid bad weather or it was a uncontrolled back heading ?
Or the boxes live the plane before he hit the water (that will contradict the BEA analysis) ?
EDIT:
Thank's CONF iture.

CONF iture;

Will be watching the Seabed Workers position closely over the next few hours. The media's interpretation of what they hear, is not always what is meant.;)

On the subject of the reanalysis of the SNA "Emeraude" sonar tapes, it would be interesting to know what data recovery technique has been used. I suspect that they have mixed a very low level 37.5kHz tone into the noise which when combined with the pinger 37.5kHz tone will provide (37.5 +/- 37.5) = 75kHz or 0. The level of the tone is critical for the mixing and the summing to take place.

mm43

CONF iture;

According to BEA's Press Release of 06/05/2010:
Since 'two hours sailing' is approx. 20 Nm; maybe Le Figaro got it wrong this time?
HN39

RTL.fr broke the news that new software had been developed to analyse the results of the sonar search made by Emeraude. The software has identified a 5 x 5 Km. area:ok:

Figaro talks about the search being focused along the planned track from the last known position and offers possible reasons why the search is now focused southwest of the last known position:

• a turnback whether to get out of the thunderstorm or to return to Rio
• an upset and spin that put them off course

mm43's work is looking better all the time:ok:

We should assume that there are very efficient digital methods available these days (as autocorrelation), that play in the frequency domain and generate a waterfall diagram of frequencies acquired.

threemiles;

Agreed, but playing in the noise is not the best playpen for digital analysis. Some analogue enhancement techniques are needed, hence my suggested mixing to extract a signal of interest. Then the waterfall diagram will show some useful 75kHz data extracted from the noise floor.

mm43

Australia's Channel 7 News said that the French Navy had recovered the Air France Black Box.........

So?

so all you have to do is read the last few messages of this thread to have an answer instead of reporting crappy journalistic sensational misinformed news ?

New search area
 

Waiting for monday's BEA press release, to get an idea of the areas examined by the Emeraude submarine during the 1st stage of the search, you may refer to the 2nd interim report delivered on the 17th of dec. 2009: http://www.bea.aero/docspa/2009/f-cp...90601e2.en.pdf .Page 82 you will find the weighted results of the search area (according to the capacity of the means deployed): the red & orange areas, west south-west of the 1st search area (explored using the TPLs, rendered in green), are presumably those probed by the Emeraude (the little isolated green area in the western part is related to the Meteo France backdrifted crash area).
Jeff

mm43, it's more likely they'd be using noise reduction technologies than trying to mix the signal to baseband or 2f as you described. I'd try using auto-correlation techniques on the signal and a delayed version of the signal, perhaps two separate pings.

Within a short time the box would be at thermal equilibrium with its resting point. So from ping to ping it's frequency would be quite stable. But the noise environment would be ever changing. So auto-correlation could use two versions of the signal to pick itself up out of the noise. I'd also look for short term correlations in the noise that could be used for nulling portions of the noise. Other techniques such as really narrow band FFT and the like may also help bring the ping up out of the noise environment.

{^_^}

Update: "Seabed Worker" - positions
 

The following are the latest available positions for Seabed Worker:-

6 May 2010 23:54z Hdg 230.3°T Spd 1.0KT 2°45'36''N 31°12'40''W
6 May 2010 22:18z Hdg 225.5°T Spd 0.7KT 2°38'08''N 31°12'45''W

The graphic below shows the positions in relation to the Last Known Position and a portion of the Zone 1 search area.

http://i44.tinypic.com/5eeiyu.jpg

The nominal search area now seems to be centered on 2°42'N 31°13'W.

If this position is where the wreckage is located, then it is reasonable to assume that an overspeed event occurred post the LKP as the a/c would appear from analysis of the ACARS messages to have been in a deep stall for over 1min prior to impact, or alternatively was airborne longer than previously thought.

mm43

Those vessel positions may correspond with the emerging news from Le Figaro, quoting a Government Official that the possibility of the plane diverting is under investigation.

Denis

Of course you are in the process of diverting after penetrating an active mesoscale event - intentional or not. My suspicion is that the track flown was not necessarily by design, and other factors had greater control.

mm43

It may also correspond to the frequence of findings of debris and bodies in the area North of the last known position as doumented in the BEA report.

http://img534.imageshack.us/img534/8...sandbodies.jpg

This one shows the total debris (white) and bodies (red) between 06-JUN-2009 and 18-JUN-2009.

http://img402.imageshack.us/img402/4...dbodies060.jpg

This one only shows debris and bodies lovated on 06-JUN-2009.

The locations have incrementally moved to the North thereafter; however, this may be a hint about the gap between 01-JUN-2009 (occurence) and the first findings on 06-JUN-2009.

Denis