I posted about this back at beginning of the VA debacle.
So you did! There it is on page 43!
What goes around comes around but don't sell yourself short: it'sentirely possible that someone at Easyjet picked up on your posting (when, it appears, no-one else did!
) and the rest may become history.
BUT CSIRO decided in 2004 (?) that VA was not going to be a viable investment (despite having had two goes at it with Dr Prata - satellite
and aircraft based) and ditched it. Why? Who knows, unless they tell us. But my guess would be that someone concluded that VA problems were too infrequent, depite already having cost airlines $250m in 'damage due to undetected ash', and the deployment cost too high for a system that would hardly ever be needed. Given the 7 -9 year gap before airlines got badly hit again, CSIRO possibly made the right judgement. More so, if in practice the system cannot detect down to
at least the 4000 microgramme level - no-one has yet said much yet about current and potential sensitivity of this system.
The Devil is in the Detail: seems to me that the current modelling system is probably accurate enough to predict where ash will get to for several days after it leaves the volcano, and at what average density over quite a large height range, given good data about how much was discharged in the eruption hour by hour. (Note the height ranges of the VAAC advisories) But the erupted volume is not accurately known and if the cloud height-range is too great, this is not so useful! The model might accurately predict an
average of <4000 microgrammes over a layer 10000 feet deep when the VA has not spread that far vertically and is in fact still concentrated into a thinner layer only 2000 feet deep.
Direct observation of the cloud appears to be the only practical answer but I have yet to see any real evidence whether the Prata system is capable of doing this and at what cost.