Green light for deployment of ESA's Mars Express radar

Radar probes of the Valles Marineris should prove enlightening.


Jacques van Oene wrote:
N=B0 08-2005 - Paris, 8 February 2005

Green light for deployment of ESA's Mars Express radar

The European Space Agency has given the green light for the MARSIS
radar on
board its Mars Express spacecraft to be deployed during the first
week of
May. Assuming that this operation is successful, the radar will
finally
start the search for subsurface water reservoirs and studies of the
Martian
ionosphere.

ESA's decision to deploy MARSIS follows eight months of intensive
computer
simulations and technical investigations on both sides of the
Atlantic.
These were to assess possible harmful boom configurations during
deployment
and to determine any effects on the spacecraft and its scientific
instruments.

The three radar booms of MARSIS were initially to have been deployed
in
April 2004, towards the end of the Mars Express instrument
commissioning
phase. They consist of a pair of 20-metre hollow cylinders, each 2.5
centimetres in diameter, and a 7-metre boom. No satisfactory ground
test of
deployment in flight conditions was possible, so that verification of
the
booms' performance had to rely on computer simulation. Just prior to
their
scheduled release, improved computer simulations carried out by the
manufacturer, Astro Aerospace (California), revealed the possibility
of a
whiplash effect before they locked in their final outstretched
positions, so
that they might hit the spacecraft.

Following advice from NASA's Jet Propulsion Laboratory (JPL), which
contributed the boom system to the Italian-led MARSIS radar
instrument, and
the Mars Express science team, ESA put an immediate hold on
deployment
until a complete understanding of the dynamics was obtained. JPL led
a
comprehensive investigation, including simulations, theoretical
studies and
tests on representative booms, the latter to assess potential aging
of the
boom material. European experts, from ESA and the former spacecraft
prime
contractor, Astrium SAS, France, worked closely with JPL throughout
the
entire investigation. An independent engineering review board,
composed of
ESA and industry experts, met in January to evaluate the findings and
advise
on 'if and when' to proceed with deployment.

The ESA review board, at its final meeting on 25 January, recommended
deployment of the MARSIS booms. The rationale for the decision was
based on
the results of the analyses, which showed the possible impact
scenarios, the
amount of energy involved, the nature of the materials, and the
physical
conditions in space. The board concluded that the risk of an impact
on the
spacecraft could not be ruled out, but that the impact energy would
be low
and the probability of a severe failure was very small.

One credible failure case is that an antenna boom could become
blocked
during deployment, either by itself or by the spacecraft. Although
means are
available to unblock a deployment, in the worst case MARSIS would
have to be
considered partially or completely lost. However, the analyses have
shown
that the Mars Express control systems would be able to cope with such
a
configuration and minimise the consequences for the other scientific
instruments.

The ESA board recommended planning the deployment for the week
beginning 2
May. However, should the remaining preparations proceed faster than
planned,
it might be feasible to start deployment during the week beginning 25
April.
An early deployment is scientifically desirable, as the evolution of
the
Mars Express orbit will allow radar measurements of the most
interesting
scientific regions on Mars to start in May 2005.

If, as expected, the deployment is successful, MARSIS will probe the
secrets
of Mars's subsurface at least until 30 November 2005, the nominal end
date
of Mars Express operations, and beyond if the mission is further
extended.


Note to editors
Mars Express was launched on 2 June 2003 and reached the planet on 25
December 2003. Since entering its operational orbit on 28 January
2004, it
has been performing studies and global mapping of the atmosphere and
surface, analysing their chemical composition, and delivering amazing
images
of Martian landscapes.

For more information please contact:
ESA Communication Department
Media Relations Office
Paris, France
Tel: +33(0)15369 7155
Fax: +33(0)1 5369 7690

Rudolf Schmidt, ESA Mars Express Project Manager
Noordwijk, The Netherlands
Tel: +31 71 565 3603

For more information about the Mars Express mission visit:
http://mars.esa.int

For more information about the Science Programme visit :
http://www.esa.int/science

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Jacques :-)
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www.spacepatches.info