NASA says its Mars Odyssey orbiter has resumed duty after switching to a set of redundant equipment not used since before the spacecraft's 2001 launch.

The swap was initiated last week in response to months of diagnostic data indicating some portions of the orbiter's instrumentation showed signs of wearing out, NASA's Jet Propulsion Laboratory in Pasadena, Calif., reported.

The orbiter carries a pair of redundant main computers -- an "A-side" and a "B-side" -- to have a backup available if one fails, with each computer having several other redundant subsystems linked to just that computer, JPL said.

"The side-swap has gone well," JPL Odyssey Project Manager Gaylon McSmith said.

"All the subsystems that we are using for the first time are performing as intended."

Odyssey is already the longest-working spacecraft ever sent to Mars, NASA said.