[meteorite-list] Will Winter Kill The Mars Rovers?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri May 5 12:33:11 2006
Message-ID: <200605051631.JAA00846_at_zagami.jpl.nasa.gov>

http://www.astronomy.com/asy/default.aspx?c=a&id=4220

Will winter kill the Mars rovers?
Spirit and Opportunity prepare for a second winter on Mars.
Michael Carroll
Astronomy Magazine
May 4, 2006

With temperatures plummeting on Mars, the twin rovers Spirit and
Opportunity have been literally racing for survival. The heart of
martian winter is less than 100 days away, and time is short for the
intrepid robots to find safe havens. During winter, the rovers must be
positioned on north-facing slopes for their solar panels to glean the
most energy possible from the diminished winter sunlight.

The situation is most critical for Spirit, which lies 12?? farther south
than its near-equatorial sibling. Spirit now receives only enough solar
power for daily drives of about an hour on flat terrain. But Spirit is
not on flat ground. The rover has been scaling the Columbia Hills,
hitting steep slopes and soft sand, since July 2004.

For the past several months, Spirit has been traversing a plateau called
Home Plate. The site has signs of an explosive origin, like a volcano or
impact. But despite Home Plate's scientific value, engineers knew they
must reposition the rover if it is going to survive winter. Operators
mapped a route to a north-facing slope, but Spirit was unable to climb
the terrain.

"There was a time when we were concerned [about reaching] a safe haven
in time," says John Callas, project manager for the Mars Exploration
Rovers. But one of Spirit's motors has now failed, leaving the right
front wheel paralyzed. "When the wheel failed on us, the terrain turned
out to be too difficult, so we had to choose a closer ridge," he says.
The rover retraced its steps and then headed toward the second site.

Spirit's solar panels continue to accumulate power-curbing dust while
temperatures drop. The picture is rosier for Opportunity. The more
equatorial site on the plains of Meridiani affords more power for the
rover's solar panels, and the flat terrain makes daily drives of 2 hours
possible. Engineers hope to arrive at the rim of Victoria Crater by
early August.

Both rovers are also showing signs of age. Each wheel motor has turned
13 million times, carrying the rovers 11 times as far as planned. The
duo has returned 150,000 images, but there has been a price.
Opportunity's instrument arm has jammed in certain positions. Spirit's
rock grinder is worn out. And because of the failure of one of Spirit's
wheel motors, the rover must negotiate the rugged landscape while
dragging the useless wheel, which is locked in position.

Scientists hope the rovers will be able to continue extensive research.
Callas says Spirit is scheduled for "a very ambitious winter campaign,"
including taking detailed panoramas using all 13 imaging filters. Spirit
is also slated to brush away layers of soil and measure the material's
properties at different depths. In addition, the rovers will study
winter clouds and their surroundings' thermal properties.

Callas likens Spirit's stationary science to the winter activities of
American pioneers: "After harvest, they'd settle down to catch up on
fixing furniture and quilting. Spirit's winter campaign gives us an
opportunity to catch up on all the science we've been putting off." If
the rovers can survive a second winter, their rich scientific return may
continue for months or years.
Received on Fri 05 May 2006 12:31:05 PM PDT