Originally Posted by ushumgal
ushumgal wrote:
Does anybody else think that they spent a surprisingly small amount of time at the new search area indicated by the analysis of the acoustic recordings? And, if I am interpreting the data correctly (which I may well not be), they didn't even cover the search area very thoroughly.
The coverage seems reasonable to me. Typically in a wide area survey, looking for at least some large pieces (55gal drum or bigger), one would operate with a side scan range of 300-500m. That means that the vehicle is seeing (at 300m range) a 600m swath, counting both sides. Because a survey is typically done with 50% overlap (each pass covers half the last pass, on average), figure that half the coverage of any pass is new ground. So that makes a swath of about 300m of new ground as the vehicle moves along.
Judging from the
REMUS 6000 Specifications - Kongsberg Maritime, the vehicle can travel at 2.5m/s, but round that down to a typical 2m/s. Thus the vehicle can cover about 600m^2/s, which is a bit more than 2km^2/hour. The vehicle can be in mission at the bottom for about 20 hours/24hours (if things go well, BEA mentioned the 20 hours, and that's consistent with the vehicle specs), which makes 40km^2/day. That is for covering every patch of ground
twice with one vehicle.
The area BEA marked on their figure, is 12km by 25km = 300km^2. If the above figures are right, that would require 7.5 vehicle-days. They have two vehicles, so they would need about 4 working days. They arrived on site May 6 and probably would have to spend a day deploying transponders and surveying their location. So they may have had the AUVs down for a good part of May 7 through May 11. That's 5 days. BEA reported that they did not survey as fast as they would like because of some vehicle problems, so it's anyone's guess how much that might have changed things. May 12 was probably used to retrieve the transponders. So a full survey is at least plausible at 300m sonar range.
Originally Posted by ushumgal
It would seem to me that, considering that this is the closest thing they've had to a solid lead for the location of the recorders, they would be concentrating in that area and working outwards from it.
That puzzles me too; but I figure I have little idea what other info they have to work with, for example, how much confidence they have in the Emeraude localization. If you start to expand that 300km^2 area on all sides, it starts to get big fast. Without some additional info on the pinger location, they probably figure that going back to the debris drift defined area is the best bet.