Image: Mars testbed
A full-scale model of the Mars Exploration Rover is used in the testbed at NASA's Jet Propulsion Laboratory.
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updated 12/2/2003 4:57:17 PM ET 2003-12-02T21:57:17

NASA’s twin Mars rovers — Spirit and Opportunity — are drawing ever closer to the Red Planet, headed for separate landings early next year. Meanwhile, teams of scientists and engineers have been hard at work, perfecting their planetary skills at driving robots across Mars and fine-tuning their abilities to conduct long-distance science.

Space.com
OVER THE LAST several months, operational readiness tests have been carried out at specially designed quarters at the Jet Propulsion Laboratory in Pasadena, Calif. — mission control for the NASA Mars Exploration Rovers.

Along with scientists, the tests known as ORTs help groom a large cadre of technicians, software experts and other specialists for the rapidly approaching “prime time” surveying of two intriguing landing zones on Mars. Each region may hold insights into whether past environments at the sites were wet enough to be hospitable to life.

Time to touchdown for the first Mars Exploration Rover is clicking away. Spirit is on course to make an airbag landing within Mars’ Gusev Crater on Jan. 3 at about 8:35 p.m. PT.

Three weeks later, on Jan. 24, Opportunity will dive onto the Martian surface at roughly 9:05 p.m. PT, rolling to a stop at a level plain called Meridiani Planum on the opposite side of Mars from Gusev.

“My team is ready. We’re trained and have our procedures down. And I can’t wait for it to happen,” said Steve Squyres of Cornell University. Squyres is principal investigator for the Athena payload — a collection of science instruments carted by each rover.

The pre-landing run-throughs have become intense training exercises for everybody, Squyres told Space.com. “We all know they are simulations … yet they are surprisingly so real. The ORTs also get us emotionally ready for what operations are going to be like on Mars,” he said.

At the Jet Propulsion Laboratory, more than 200 individuals participate in the practice drills. Teams typically use a full-fidelity rover planted in a Marslike setting, complete with plentiful amounts of sand and rock. In a past session, two rovers were operated simultaneously.

Over the months, uplink and downlink commands have been simulated and evaluated. Software has been tested and retested. Also rehearsed is using science gear mounted on the Earth-based rovers, matching similar equipment now en route to the Red Planet. Even press briefings have been staged, Squyres said.

“We learn how to streamline and improve our processes … how to better utilize the operations facilities … even down to seating arrangements in certain rooms. We’ve gotten smarter and better as a result of the ORTs. They have been incredibly necessary and valuable.”

FIENDISHLY COMPLICATED

The toughest challenge ahead, Squyres noted, is the time from when they first hear from a rover as it moves onto Mars’ surface. “Getting those six wheels in the dirt is one of the most complicated things anyone has ever tried to do with a planetary spacecraft,” he said.

Once safely stopped on Mars, with airbags deflated and lander petals outstretched, each mechanized rover must undergo yogalike gymnastics of sorts, unfolding itself into a ready-for-action status.

“It’s a fiendishly complicated process. We have to be very, very cautious and methodical how we carry it out. The success of the remainder of the mission is dependent on getting that part right,” Squyres explained. First photos from a rover are not likely for roughly a day after landing, he said.

Getting ready at JPL for the planetary putdowns of Mars rovers involves both “elves” and “gremlins.” They are test personnel who keep rover operators on their toes dealing with a variety of make-believe Mars landing scenarios.

“We call them elves when they are nice to us … gremlins when they are not,” Squyres said.

For example, one of those set-ups had teams coping with a weirdly tilted rover.

“They almost completely surrounded the rover with very big, very nasty rocks. So the engineers had to move a petal on the lander in such a way that we could drive the rover down backwards … like backing down your driveway. It was a somewhat ‘off nominal’ way of getting off the lander. That one was exciting,” Squyres said.

TROUBLESHOOTING A GLITCH

One instrument glitch was found in-flight on a Mars Exploration Rover.

Spirit’s Mössbauer spectrometer — a tool for identifying the types of iron-bearing minerals in rocks and soil — returned data in August showing the instrument was not up to snuff. A drive system that rapidly vibrates a gamma-ray source back and forth inside the instrument appeared to show partial restriction in its motion.

“We spent months troubleshooting. We proceeded very slowly and cautiously. The instrument doesn’t have to take data until we get to Mars. So there was no rush,” Squyres said.

By changing certain parameters on the device its is now functioning normally. “That’s a big relief, frankly,” Squyres said. “But I’m not going to breathe easy on this instrument … or breathe easy on any of the instruments until we’ve been through the landing process and we’re down on the surface,” he said.

As for the upcoming landings, Squyres said he’s personally waited 16 years for this to happen. “I’m ready to get it on…I really am,” he said.

The months of journey for both Mars Exploration Rovers have not been trouble-free.

Mark Adler, Spirit mission manager at JPL, said the sun’s recent antics did cause some problems with Spirit and Opportunity as they hurtled outward to Mars. There were no lasting effects, however, from the solar activity, aside from a very small degradation in the output from solar arrays on each of the Mars-bound craft.

“That level of degradation is of no concern. The star scanners [used for navigation] on both vehicles were unable to function during the peak of the activity, but they are back in operation now and working fine,” Adler reported. In addition, solar activity necessitated shutdown of the Mars Exploration Rover computers, pulling their power for a short time, then powering them back up and rebooting. Those operations were completed successfully on both rovers.

“We continue to be vigilant for more solar activity, and we’re prepared to operate through it if it comes. Fortunately though, the sun appears to have calmed down … for now,” Adler said.

FIRST PLUNGE

“Both spacecraft are in excellent health,” Adler said. “We completed the third trajectory correction maneuver on Spirit. The third maneuver on Opportunity was small enough to cancel, so we did,” he told Space.com.

Adler said the dual Mars probes are now on a trajectory to enter the Martian atmosphere, very close to, though probably not exactly on the intended targets. “So we have two more maneuvers scheduled for each … at eight days and two days before entry to fine-tune their trajectories to Gusev Crater and Meridiani Planum.”

Spirit recently received a new version of flight software.

“It’s kind of like giving the spacecraft a brain transplant,” Adler said. This is the final version of the software for entry, descent, and landing, as well as for the surface mission. If necessary, there is the option to patch the software after landing. Similarly, Opportunity is to receive the same software, he said.

“The operations team has completed all but one of our approach, entry, descent and landing rehearsals. We have one more short one to do in December,” Adler said. “All in all, we’re ready and our spacecraft are ready for the activities in December and early January, and for the first plunge the night of Jan. 3,” he said.

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