JPL code eases rover's Mars landing

The first of NASA's twin Mars Exploration Rovers successfully landed this month using software that wasn't completed until well into the flight.

The Jet Propulsion Laboratory in Pasadena, Calif., uploaded a rebuilt software package to the Spirit rover in early December, said Roger Klemm, a JPL flight software developer. The other rover, Opportunity, later got the same rebuild.

The rovers couldn't launch with finished code last summer because NASA needed to further test the atmospheric entry and descent instructions, said Klemm. Each software uplink took about 24 hours at a rate of 2 Kbps.

Opportunity is scheduled to land in a different region Jan. 24. More patches will be transmitted for the science mission if necessary, Klemm said.

Both rovers' radiation-hardened 20-MHz Rad 6000 CPUs run Wind River Systems Inc.'s VxWorks operating system. Spirit's onboard computer has only 128M of memory, so 'there's not a whole lot of instructions we can give it,' said Mike Deliman, a technical staff member at the Alameda, Calif., company.

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