[meteorite-list] Soft Ground Puts Spirit in Danger Despite Gain in Daily Energy

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 13 May 2009 17:49:58 -0700 (PDT)
Message-ID: <200905140049.RAA04028_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2009-082

Soft Ground Puts Spirit in Danger Despite Gain in Daily Energy
Jet Propulsion Laboratory
May 11, 2009

Mars Exploration Rover Mission Status Report

PASADENA, Calif. -- The five wheels that still rotate on NASA's Mars
Exploration Rover Spirit have been slipping severely in soft soil during
recent attempts to drive, sinking the wheels about halfway into the ground.

The rover team of engineers and scientists has suspended driving Spirit
temporarily while studying the ground around the rover and planning
simulation tests of driving options with a test rover at NASA's Jet
Propulsion Laboratory, Pasadena, Calif.

"Spirit is in a very difficult situation," JPL's John Callas, project
manager for Spirit and its twin rover, Opportunity, said Monday. "We are
proceeding methodically and cautiously. It may be weeks before we try
moving Spirit again. Meanwhile, we are using Spirit's scientific
instruments to learn more about the physical properties of the soil that
is giving us trouble."

Both Spirit and Opportunity have operated more than five years longer
than their originally planned missions of three months on Mars and have
driven much farther than designed. The rover team has so far developed
ways to cope with various symptoms of aging on both rovers.

Spirit has been driving counterclockwise from north to south around a
low plateau called "Home Plate" for two months. The rover progressed 122
meters (400 feet) on that route before reaching its current position.

In the past week, the digging-in of Spirit's wheels has raised concerns
that the rover's belly pan could now be low enough to contact rocks
underneath the chassis, which would make getting out of the situation
more difficult. The right-front wheel on Spirit stopped working three
years ago. Driving with just five powered wheels while dragging or
pushing an immobile wheel adds to the challenge of the situation.

Favorably, three times in the past month, wind has removed some of the
dust accumulated on Spirit's solar panels. This increases the rover's
capability for generating electricity.

"The improved power situation buys us time," Callas said. "We will use
that time to plan the next steps carefully. We know that dust storms
could return at any time, although the skies are currently clear."

Behavioral problems that Spirit exhibited in early April -- episodes of
amnesia, computer resets and failure to wake for communications sessions
-- have not recurred in the past three weeks, though investigations have
yet to diagnose the root causes.

JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Exploration Rover project for NASA's Science Mission
Directorate, Washington.

Media contact: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster at jpl.nasa.gov

2009-082
Received on Wed 13 May 2009 08:49:58 PM PDT