Comments: download file (pdf )
Ref.: SiPLAB Report 01/01, FCT, University of Algarve,2001.
Abstract
The TOMPACO project (TOMPACO stands for ''TOMografia PAssiva COstiera''
-
Passive Coastal Tomography), aims at developing and testing ocean
tomography
techniques for obtaining a dense space-time acoustic griding at low
cost,
by relaxing the control on the source signal and geometry. In practice
this
means using alternative acoustic sources readily available in the ocean
such
as, for example, the noise radiated by ships of opportunity close or
crossing
the area of interest. The main challenge faced by passsive
tomography,
and therefore by TOMPACO, is to account for the unpredictibility of the
sound
source in the tomographic procedure. That unpredictibility relates both
to
the source emitted signal and to the source-receiver geometry. The
study of
the impact of these two factors in the acoustic tomographic inversion
process
is the main goal of the TOMPACO project.
The INTIFANTE'00 sea trial (INTIFANTE is a madeup acronym from INTImate
and
inFANTE) was carried out in the vicinity of Setúbal, situated
approximately
50 km to the south of Lisbon, in Portugal, during the period from 9 to
29
October, 2000. This sea trial served a number of specific purposes
under
the leading projects INTIMATE and INFANTE, but one day was reserved to
acquire
acoustic data to test the passive tomography concept under the TOMPACO
project.
The experiment area was a rectangular box situated in the border of the
continental
platform with depths varying from 60 to 140 m and including a sharp
submarine
canyon (the Setúbal canyon) with depths reaching over 500 m. As
an
overview of the thecnical aspects involved in the experiment, it can be
referred
that acoustic signals were transmitted with an acoustic projector from
onboard
NRP D. Carlos I and received on a moored 16 hydrophone-4m spacing
Vertical
Line Array (VLA). The acoustic aperture of the vertical array was
located
between 30 and 90 m in a 120 m water column. The acoustic signals
received
in the VLA were transmitted via an RF link to the research ship NRP D.
Carlos
I, processed, monitored and stored. Various signals were emitted by the
sound
projector ranging from linear frequency modulated (LFM) 2 second
long
upsweeps, to broadband computer generated white noise. Recordings were
also
made with the NRP D. Carlos I acting as source signal for the passive
tomography
testing purpose.