[meteorite-list] Rewrite of Onboard Memory Planned for NASA Mars Orbiter (MRO)

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=4757

Rewrite of Onboard Memory Planned for NASA Mars Orbiter
Jet Propulsion Laboratory
October 29, 2015

Mission Status Report

Tables stored in flash memory aboard NASA's Mars Reconnaissance Orbiter 
(MRO) tell locations of Earth and the sun for the past 10 years, but not 
their locations next year. That needs to be changed. Carefully.

The long-lived orbiter relies on these tables to recover in the event 
of an unplanned computer shutdown. When the spacecraft computer reboots, 
it checks to see where it should position the antenna for communication 
and, even more critically, where it should position the solar arrays for 
power. Flash memory is "nonvolatile" -- meaning that it retains information 
even while the power is off -- so it works well for this backup role.

The tables were loaded before the spacecraft's Aug. 12, 2005, launch and 
they cover location information through July 12, 2016. To be safe, the 
mission team plans to begin updating them next week. Doing so will require 
intentionally rebooting the onboard computer during a one-week suspension 
of MRO's science observations and communication relay duty. Both of NASA's 
active Mars rovers will use a different NASA Mars orbiter, Odyssey, for 
relaying their data to Earth while MRO is out of service.

Sixteen times since launch, MRO has experienced unplanned reboots that 
relied on the stored tables for recovery of the spacecraft. Managers anticipate 
that such events will continue to happen in coming years.

"Updating what's in the memory is essential for spacecraft safety and 
for extending the mission," said MRO Project Manager Dan Johnston at NASA's 
Jet Propulsion Laboratory, Pasadena, California.

To update the location tables, engineers will rewrite the entire content 
of the nonvolatile memory on the spacecraft. The orbiter has two identical 
computers for redundancy, with only one of them active at a time. Each 
computer has its own nonvolatile memory unavailable to the other, so the 
rewrite needs to be done twice. The "Side B" computer has been active 
since an unplanned side swap in April 2015. The plan is to rewrite that 
computer's nonvolatile memory starting on Nov. 2. The procedure for "Side 
A" will follow in early 2016.

The contents of each computer's 256 megabytes of nonvolatile memory include 
backup copies of vital computer-operation files. "It's the fundamental 
operating system of the spacecraft. That's what adds risk," Johnston said. 
"Just like with your home computer: If you mess with the operating system, 
the computer won't work."

Since MRO launched, the mission team has rewritten the nonvolatile memory 
just once, in 2009. The Side B rewrite next week will follow procedures 
similar to those used successfully in 2009, but with an added safeguard. 
After a partial rewrite, an intentional reboot will be commanded, to confirm 
that the newly recorded information is usable. If it is not, sufficient 
information from the 2009 rewrite would still be still available as backup 
for a successful reboot. After confirmation that the partial rewrite is 
successful, the rest of the memory contents will be replaced.

Though it is already in its fourth mission extension, MRO could remain 
a cornerstone of NASA's Mars Exploration Program fleet for years to come. 
The longevity of the mission has given researchers tools to study seasonal 
and longer-term changes on Mars, including recently discovered seasonal 
activity of salty liquid water. Among other current activities, the orbiter 
is examining possible landing sites for future missions to Mars and relaying 
communications to Earth from Mars rovers.

JPL, a division of the California Institute of Technology in Pasadena, 
manages the MRO Project for NASA's Science Mission Directorate, Washington. 
Lockheed Martin Space Systems in Denver built the orbiter and supports 
its operations. For more information about MRO, visit:

http://www.nasa.gov/mro

http://mars.nasa.gov/mro

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

Dwayne Brown / Laurie Cantillo
NASA Headquarters, Washington
202-358-1726 / 202-358-1077
dwayne.c.brown at nasa.gov / laura.l.cantillo at nasa.gov

2015-335