[meteorite-list] Mars Express Deploys Second Radar Boom

[Ron Baalke]

http://www.newscientistspace.com/article.ns?id=dn7523

Mars Express deploys second radar boom
Maggie McKee
New Scientist
June 15, 2005

The second of two identical radar booms has been deployed on Europe's
Mars Express spacecraft - but it is not yet clear if the operation was
successful. If it was, the antenna could begin scouting for underground
water on Mars within a week.

Mission managers in Darmstadt, Germany, deployed the 20-metre-long boom
on 14 June at 1130 GMT. After a series of manoeuvres designed to warm
the boom evenly in sunshine, the spacecraft reoriented itself towards
Earth about two hours later and began beaming data to mission control.

"It's always good to see your spacecraft back under control," says Fred
Jansen, the spacecraft's mission manager. "But we know from the first
boom's deployment that this does not tell the full story, so we are not
declaring the operation successful yet."

That first boom in the MARSIS (Mars Advanced Radar for Subsurface and
Ionosphere Sounding) experiment popped out of its storage box on 4 May.
But a few days later, engineers discovered one of its outer hinges had
failed to lock into place during deployment, leaving a slight kink in
the antenna.

Mission managers suspected the coldness of space played a role in the
problem, so on 10 May they exposed the crooked boom to the Sun for a few
minutes. The warming trick worked - the boom straightened and locked in
place - but an analysis showed the spacecraft itself could become
unstable if a kink were to occur on an inner segment of the second boom.
So mission planners postponed the deployment of that boom - which is
crucial for the instrument to function - to study the issue.
          
Hinge heater

In deploying boom 2, mission managers set Mars Express rotating very
slowly with the stored boom facing generally towards the Sun. Then, they
deployed the boom and kept rotating the spacecraft so that, in half an
hour, the boom rotated through 180 degrees.

"So if you assume a hinge is at an angle somewhere, the Sun would
illuminate all the hinges and heat them up," Jansen told New Scientist.

Managers will study data from the spacecraft's gyroscopes, which measure
its rotation, to see whether the boom deployed straight. They hope to
finish their analysis of the deployment on Thursday.

If the procedure was a success, mission officials will deploy the third
and final boom on 17 June. This is a 7-metre-long pole that will help
determine whether the reflected radio waves are coming from underground,
but it is not critical to the mission. If all goes to plan, the
experiment is set to record its first data on 21 June, as part of its
initial commissioning phase.

MARSIS was originally scheduled to be deployed in April 2004 but was
delayed for a year over concerns that the springy booms could have hit
and damage the spacecraft during deployment. But further Earth-based
tests allayed those fears.

Scientists hope MARSIS will discover whether the water that once carved
canyons on the Red Planet's surface has seeped into underground
reserves. Such reserves might harbour life or be used to supply future
crewed missions to Mars.