[meteorite-list] Test of Spare Wheel Puts Mars Odyssey on Path to Recovery

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 14 Jun 2012 17:57:27 -0700 (PDT)
Message-ID: <201206150057.q5F0vRhx014485_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2012-176

Test of Spare Wheel Puts Orbiter on Path to Recovery
Jet Propulsion Laboratory
June 14, 2012

Mars Odyssey Mission Status Report

PASADENA, Calif. -- In a step toward returning NASA's Mars Odyssey
orbiter to full service, mission controllers have tested a spare
reaction wheel on the spacecraft for potential use with two other
reaction wheels in adjusting and maintaining the spacecraft's orientation.

After more than 11 years of non-operational storage, the spare reaction
wheel passed preliminary tests on Wednesday, June 12, spinning at up to
5,000 rotations per minute forward and backward. Odyssey engineers plan
to substitute it for a reaction wheel they have assessed as no longer
reliable. That wheel stuck for a few minutes last week, causing Odyssey
to put itself into safe mode on June 8, Universal Time (June 7, Pacific
Time). Safe mode is a precautionary status with reduced activity.

"We are taking steps to assess the replacement of the troublesome wheel
with the spare that Odyssey has been carrying for exactly this purpose,"
said Mars Odyssey Project Manager Gaylon McSmith of NASA's Jet
Propulsion Laboratory, Pasadena, Calif. "If the assessment results are
positive, this will put us on a path toward resuming full use of Odyssey."

Like many other spacecraft, Odyssey uses a set of three reaction wheels
to control its attitude, or which way it is facing relative to the sun,
Earth or Mars. Increasing the rotation rate of a reaction wheel inside
the spacecraft causes the spacecraft itself to rotate in the opposite
direction. The configuration in use since launch combines the effects of
three wheels at right angles to each other to provide control in all
directions. The orbiter carries a fourth reaction wheel skewed at angles
to all three others so that it can be used as a substitute for any one
of them. This spare wheel had not rotated since before Odyssey's April
7, 2001, launch.

Odyssey can also use thrusters to control its attitude. Reaction wheels
offer the advantage of running on renewable electricity from the
orbiter's solar array, rather than drawing on the finite supply of
thruster fuel. They also provide more precise control of pointing, which
can enable higher data-rate communications through the orbiter's
directional antenna.

Odyssey has worked at Mars for more than 10 years, which is longer than
any other Mars mission in history. Besides conducting its own scientific
observations, it serves as a communication relay for robots on the
Martian surface. NASA plans to use Odyssey and the newer Mars
Reconnaissance Orbiter as communication relays for the Mars Science
Laboratory mission during the landing and Mars-surface operations of
that mission's Curiosity rover.

Odyssey is managed by NASA's Jet Propulsion Laboratory, Pasadena, for
NASA's Science Mission Directorate in Washington. Lockheed Martin Space
Systems in Denver built the spacecraft. JPL and Lockheed Martin
collaborate on operating the spacecraft. For more about the Mars Odyssey
mission, visit: http://mars.jpl.nasa.gov/odyssey .

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

2012-176
Received on Thu 14 Jun 2012 08:57:27 PM PDT