[meteorite-list] Spirit Rover: Rear Wheel Trouble Continues

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 10 Dec 2009 16:22:00 -0800 (PST)
Message-ID: <200912110022.nBB0M0ZW015626_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2009-191

Rear Wheel Trouble Continues
Jet Propulsion Laboratory
December 10, 2009

Results of diagnostic tests on Spirit's right-rear wheel on Sol 2109
(Dec. 8, 2009) continue to indicate a troubled wheel, which may leave
the rover with only four operable wheels.

The Sol 2109 plan included a check of the grind motor of Spirit's rock
abrasion tool (RAT) because it shares the same motor controller as the
right-rear wheel. It also included rotor resistance tests on the
right-rear motor at three temperatures using opposite voltage polarity
from earlier tests, backward and forward commanded motion of the
right-rear wheel, and a check of rotor resistance on all other operating
wheels. The RAT motor appears okay, although a more exhaustive test will
be tried later. The right-rear wheel rotor resistance tests continue to
show very elevated resistance, although not as high as in previous
tests, and exhibiting a curious voltage-dependent effect. No motion of
the right-rear wheel occurred during the backward commanded motion. The
forward motion was not executed since the initial backward motion did
not occur. The rotor resistances on all the other operating wheels are
nominal.

The plan ahead, still being developed, will likely include more rotor
resistance tests, an attempt to apply higher voltage to the right-rear
wheel to see if any movement will occur, and a check of the right-front
wheel to confirm its status and to see if it may offer insight into the
right-rear wheel's condition. Further ahead, steering tests will be
considered to explore an external jam as a possible explanation.

Concurrent with this, the project is exploring whether any meaningful
rover motion would be possible with only four operable wheels. Spirit
lost the use of its right front wheel in 2006.

Because of the current rover tilt, the environmental conditions and dust
accumulation on the solar arrays, Spirit is at risk of inadequate power
for surviving through the next southern Mars winter, which reaches
solstice on May 13, 2009. Even if extrication is not possible, some
limited rover motion may be able to improve rover tilt and increase the
chance of winter survival.
Received on Thu 10 Dec 2009 07:22:00 PM PST