[meteorite-list] Mars Express Radar Deployment Postponed

Ron Baalke baalke at zagami.jpl.nasa.gov
Thu Apr 29 17:21:40 EDT 2004


Mars Express radar deployment postponed
European Space Agency
29 April 2004

The MARSIS team has advised ESA to delay the
deployment of the MARSIS radar instrument on board
Mars Express, scheduled for this week.
New and improved computer models suggest that, during
deployment, the radar booms may swing back and forth
with larger amplitudes than previously expected. If this
happened, the booms might come too close to delicate
components of the spacecraft body. Further simulations and
tests are under way to better understand the situation.  
The two main radar booms are 20-metre long hollow cylinders, 
of 2.5 centimetres diameter, folded up in a box like a 
concertina (accordion). When the box is opened, the elastic 
energy of the compressed glass-fibre booms will let
them unfold like a jack-in-the-box.
After the booms spring out, they will eventually lock in a 
straight line, taking up the shape that they had before being 
folded into the box. The deployment procedure of each boom is 
expected to last about 10 minutes.
Simulations carried out four years ago by the radar boom's 
manufacturer, Astro Aerospace, California, USA, indicated 
that the deployment should be smooth, without significantly 
swinging back and forth. However, the radar team has now
advised ESA that a new and refined analysis of the boom 
dynamics indicates that a sort of "backlash" might take 
place before the boom locks into its position.
Although a successful deployment is not in question, Mars 
Express mission managers want to make sure that the booms 
are not subjected to excessive mechanical stress and that 
they do not interfere with the spacecraft as they deploy. 

The MARSIS team and their industrial contractors are now 
performing further tests and simulations to confirm that 
the deployment will have no impact on the safety of the 
spacecraft. These simulations will then be reviewed by ESA's
experts. Based on the results, expected within a few weeks, 
ESA will decide when and how to activate MARSIS.
MARSIS will study the sub-surface of Mars to a depth of a 
few kilometres. The instrument's antennas will send radio 
waves towards the planet and analyse how they are reflected 
by any surface that they encounter. In this way, MARSIS
can investigate the sub-surface mineralogical composition 
and will reveal the presence of any underground reservoir 
of water or ice.

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