NASA Marks Milestone For Long-Lived Spacecraft
NASA rovers Spirit and Opportunity may still have big
achievements ahead as they approach the fifth anniversaries of
their memorable landings on Mars.
Of the hundreds of engineers and scientists who cheered at
NASA's Jet Propulsion Laboratory in Pasadena, CA on January 3,
2004, when Spirit landed safely, and 21 days later when Opportunity
followed suit, none predicted the team would still be operating
both rovers in 2009.
"The American taxpayer was told three months for each rover was
the prime mission plan," said Ed Weiler, associate administrator
for NASA's Science Mission Directorate at NASA Headquarters in
Washington. "The twins have worked almost 20 times that long.
That's an extraordinary return of investment in these challenging
budgetary times."
The rovers have made important discoveries about wet and violent
environments on ancient Mars. They also have returned a
quarter-million images, driven more than 21 kilometers (13 miles),
climbed a mountain, descended into craters, struggled with sand
traps and aging hardware, survived dust storms, and relayed more
than 36 gigabytes of data via NASA's Mars Odyssey orbiter. To date,
the rovers remain operational for new campaigns the team has
planned for them.
"These rovers are incredibly resilient considering the extreme
environment the hardware experiences every day," said John Callas,
JPL project manager for Spirit and Opportunity. "We realize that a
major rover component on either vehicle could fail at any time and
end a mission with no advance notice, but on the other hand, we
could accomplish the equivalent duration of four more prime
missions on each rover in the year ahead."
Occasional cleaning of dust from the rovers' solar panels by
Martian wind has provided unanticipated aid to the vehicles'
longevity. However, it is unreliable aid. Spirit has not had a good
cleaning for more than 18 months. Dust-coated solar panels barely
provided enough power for Spirit to survive its third
southern-hemisphere winter, which ended in December.
"This last winter was a squeaker for Spirit," Callas said. "We
just made it through."
With Spirit's energy rising for spring and summer, the team
plans to drive the rover to a pair of destinations about 183 meters
(200 yards) south of the site where Spirit spent most of 2008. One
is a mound that might yield support for an interpretation that a
plateau Spirit has studied since 2006, called Home Plate, is a
remnant of a once more-extensive sheet of explosive volcanic
material. The other destination is a house-size pit called
Goddard.
"Goddard doesn't look like an impact crater," said Steve Squyres
of Cornell University, in Ithaca, NY. Squyres is principal
investigator for the rover science instruments. "We suspect it
might be a volcanic explosion crater, and that's something we
haven't seen before."
A light-toned ring around the inside of the pit might add
information about a nearby patch of bright, silica-rich soil that
Squyres counts as Spirit's most important discovery so far. Spirit
churned up the silica in mid-2007 with an immobile wheel that the
rover has dragged like an anchor since it quit working in 2006. The
silica was likely produced in an environment of hot springs or
steam vents.
For Opportunity, the next major destination is Endeavour Crater.
It is approximately 22 kilometers (14 miles) in diameter, more than
20 times larger than another impact crater, Victoria, where
Opportunity spent most of the past two years. Although Endeavour is
about 12 kilometers (7 miles) from Victoria, it is considerably
farther as the rover drives on a route evading major obstacles.
Since climbing out of Victoria four months ago, Opportunity has
driven more than a mile of its route toward Endeavour and stopped
to inspect the first of several loose rocks the team plans to
examine along the way. High-resolution images from NASA's Mars
Reconnaissance Orbiter, which reached Mars in 2006, are helping the
team plot routes around potential sand traps that were not
previously discernible from orbit.
"We keep setting the bar higher for what these rovers can do,"
said Frank Hartman, a JPL rover driver. "Once it seemed like a
crazy idea to go to Endeavour, but now we're doing it."
Squyres said, "The journeys have been motivated by science, but
have led to something else important. This has turned into
humanity's first overland expedition on another planet. When people
look back on this period of Mars exploration decades from now,
Spirit and Opportunity may be considered most significant not for
the science they accomplished, but for the first time we truly went
exploring across the surface of Mars."