[meteorite-list] MSL Computer Issue Resolved

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 9 Feb 2012 11:49:22 -0800 (PST)
Message-ID: <201202091949.q19JnMsf024498_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2012-038

Spacecraft Computer Issue Resolved
Jet Propulsion Laboratory
February 09, 2012

Mars Science Laboratory Mission Status Report

PASADENA, Calif. -- Engineers have found the root cause of a computer
reset that occurred two months ago on NASA's Mars Science Laboratory and
have determined how to correct it.

The fix involves changing how certain unused data-holding locations,
called registers, are configured in the memory management of the type of
computer chip used on the spacecraft. Billions of runs on a test
computer with the modified register configuration yielded no repeat of
the reset behavior. The mission team made this software change on the
spacecraft's computer last week and confirmed this week that the update
is successful.

The reset occurred Nov. 29, 2011, three days after launch, during use of
the craft's star scanner. The cause has been identified as a previously
unknown design idiosyncrasy in the memory management unit of the Mars
Science Laboratory computer processor. In rare sets of circumstances
unique to how this mission uses the processor, cache access errors could
occur, resulting in instructions not being executed properly. This is
what happened on the spacecraft on Nov. 29.

"Good detective work on understanding why the reset occurred has yielded
a way to prevent it from occurring again," said Mars Science Laboratory
Deputy Project Manager Richard Cook of NASA's Jet Propulsion Laboratory,
Pasadena, Calif. "The successful resolution of this problem was the
outcome of productive teamwork by engineers at the computer manufacturer
and JPL."

The Mars-bound spacecraft performed a brief alignment activity using its
star scanner and sun sensor on Jan. 26. During the alignment
observations, the star scanner detected Mars.

"Our target is in view," said JPL's Steve Collins, attitude control
subsystem engineer for Mars Science Laboratory's cruise from Earth to Mars.

The spacecraft began normal use of its star tracker and true celestial
navigation this week after its software update.

The Mars Science Laboratory mission will use its car-size rover,
Curiosity, to investigate whether the selected region on Mars inside
Gale Crater has offered environmental conditions favorable for
supporting microbial life and favorable for preserving clues about
whether life existed. Curiosity will land on Mars on Aug. 6, 2012,
Universal Time and Eastern Daylight Time (evening of Aug. 5, Pacific
Daylight Time).

The spacecraft's cruise-stage solar array is producing 704 watts. The
telecommunications rates are 1 kilobit per second for uplink and 800
bits per second for downlink. The spacecraft is spinning at 1.97
rotations per minute.

As of 9 a.m. PST (noon EST, or 1700 Universal Time) on Friday, Feb. 10,
the spacecraft will have traveled 127 million miles (205 million
kilometers) of its 352-million-mile (567-million-kilometer) flight to
Mars. It will be moving at about 17,800 miles per hour (28,600
kilometers per hour) relative to Earth and at about 63,700 mph (102,500
kilometers per hour) relative to the sun.

JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Science Laboratory mission for the NASA Science Mission
Directorate, Washington.

More information about Curiosity is online at: http://www.nasa.gov/msl
and http://mars.jpl.nasa.gov/msl/ . You can follow the mission on
Facebook at: http://www.facebook.com/marscuriosity and on Twitter at:
http://www.twitter.com/marscuriosity .

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

2012-038
Received on Thu 09 Feb 2012 02:49:22 PM PST