The solution: Delete excess files and send a patch instructing the rovers how to use their flash and random memories more conservatively.
This patch was also sent to the second rover, Opportunity, which had meanwhile experienced a flawless landing on Jan. 24. That mobile explorer maintained communications with Earth even while it was bouncing to a stop. Then it flipped itself upright and began sending back images from its 20-megapixel stereo cameras.
By the end of January, the Mars exploration programs head scientist, Steve Squyres, said he was optimistic both rovers ultimately will work well beyond the three months originally planned. "We built margin [of error] on top of margin [of error], specifically to allow for the fact that things go wrong on a place like Mars," he says.
The resuscitation of Spirit continued a record of long-distance network recoveries for the space program. In 1990, the Galileo spacecraft sent to Jupiter suffered what could have been a mission-ending failure when its umbrella-like main antenna failed to unfold properly, but JPL managed to reprogram the spacecraft in flight. In that case, mission managers sent compression software that allowed Galileo to transmit data and high-resolution images over a backup antenna.
The rehabilitation of Spirit also came as explorations of Mars were putting unprecedented demands on the Deep Space Network. If Beagle 2 had remained in contact, NASA also would have assisted the Europeans with communications for that lander.
To accommodate Spirit and Opportunity, the Deep Space Network has to maintain round-the-clock communication. Because they are on opposite sides of the planet, the two rovers operate on roughly opposite shifts. When one is in daylight, it gathers power through its solar panels, while the other powers down for the night.
For the $860-million mission to be completely successful, scientists wanted both rovers actively searching for signs that liquid water existed on Mars.
But, in any event, sending twin rovers to Mars served as insurance for NASA in case one robot was lost-redundant outposts of the 100-million-mile network.