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MER Update

Mars Exploration Rovers Update: Spirit Gets 'Kicks' on Route 66 Opportunity Solves Martian Mystery

Posted by A.J.S. Rayl

17-04-2004 12:00 CDT

Topics: Opportunity, Spirit, mission status, Mars Exploration Rovers

This week, the Mars Exploration Rovers team successfully installed the new flight software it was uploading to Spirit and Opportunity last weekend. Now, the rovers have enhanced capabilities that should make their remaining Martian sols even safe and more productive, announced Jan Chodas, flight software manager, at the weekly news briefing at the Jet Propulsion Laboratory (JPL).

The transfer was "a major accomplishment," Chodas said, and both rovers made a "successful transition," with Spirit switching to the new version successfully on Monday, and Opportunity on Tuesday. "I'm happy to say that the new flight software version is working flawlessly," she added.

Although the engineers had allotted four "science stand down" days for the uploading/rebooting process for each rover, they completed the procedures on both Spirit and Opportunity in three days, and the rovers didn't miss a beat. "The science team did have some bonus science observations in the queue ready to go and we were able to fill in [the fourth days] with those," reported Chodas.

The new flight software augments the rovers in three key ways, offering Spirit and Opportunity better mobility, a 'deep sleep' mode, and more "robustness' in their memory.

Mobility: With the mobility enhancements written into the new flight software, the rovers will be able to rove further and faster, especially in autonomous navigation mode, where the rovers drive themselves. The previous autonomous navigation software sometimes got stuck when it detected a hazard that the rover couldn't navigate around.

The new version will allow the rovers to turn in place to find the best possible path, reducing how often they have to stop, take images and generate new three-dimensional maps to determine the path to take. And, Chodas added: "These mobility enhancements [will] allow the rovers to drive further per sol than they were able to before." In fact, the new software will nearly double the rovers' per-hour rate, from 55 feet to 105 feet or 16 to 32 meters.

Deep Sleep: The 'deep sleep' mode was added mainly to resolve the battery drain caused by a heater on Opportunity's instrument deployment device (IDD) or robotic arm that is stuck in the 'on' position. In 'deep sleep mode, the batteries are turned off to prevent any power from getting to the heater, which mitigates the battery drain problem. "[This] will allow [the rover] to save the energy that previously was being used by the heater overnight," said Chodas. Rover controllers do not anticipate using the 'deep sleep' mode on Spirit, but if, for any reason, they need or want to, they have the option.

Robustness: Other additions to the new flight software will allow the rovers to recover more easily from a memory anomaly like the one that occurred on Spirit two weeks into her mission and which put her essentially out of commission for nearly a week and a half. Basically, Spirit's flash memory became overloaded and she went into a vicious cycle of errors and reboots. Although certain operational processes and new software had already been instituted to prevent something like this from ever happening again, this new flight software includes additional 'safety nets' that would allow the rovers to autonomously react to such an anomaly and recover to a more stable state.

One goal of the science-stand down time, Chodas said, was to download many of the files that had already been collected and stored in the flash memory. "Both Spirit and Opportunity downloaded close to 700 megabits each of data from their flash [memory], so now we have a lot more room to continuing gathering science data, so we now have about 2/3 of flash memory available," she informed.

To date, the 18 cameras on the two rovers have returned some 24,000 images, 16,000 of which are panorama camera (PanCam) images -- a full 3 gigabytes of data.

Seventy-five megabits of that 3 gigabytes went into the Lion King Panorama -- one of the mission success 360-degree, color mosaic panoramas acquired [by Opportunity] on Sols 58 and 60, reported Jason Soderblom, a science team collaborator from Cornell University. Nearly 600 images, taken through six different filters, produced the stunning panorama in a color close to what you would see if you were standing on Mars. The panorama -- which gives a good sense of how wind has uncovered the outcrop at the upwind side of the crater, deposited sand in the downwind side of the crater and bright Martian dust in the wind shadow of the crater -- will be studied and used by Mars scientists for decades to come.

SPIRIT FROM GUSEV CRATER
Sols 97 - 102

Before the MER team began uploading the files for the new software to Spirit a week ago Thursday, they positioned the IDD so that the Mössbauer spectrometer was on the rock Route 66 and the alpha particle x-ray spectrometer (APXS) was pointed up into the atmosphere, according to plan. Since these spectrometers benefit from the opportunity of being able to measure composition over time, the team decided to conduct some long integrations during the 'down time' sols used for uploading the files.

On Monday - Spirit's Sol 98, mission controllers gave the 'go' to reboot the rover's computer and start running the new software. The command was sent, and a little over a half hour later, engineers heard the carrier 'beep' that indicated Spirit had received the command. Spirit went to sleep for several minutes after that, and then woke up, rebooting into the new software. The rover then initiated a high-gain antenna (HGA) session at 12:30 p.m. Mars local solar time, which confirmed for the engineers saw that the new version of the rover software was running properly.

Spirit returned to regular operations on Tuesday - Sol 99, beginning her new day at Gusev Crate by conducting a systematic ground survey with her miniature thermal emission spectrometer (mini-TES). After that, the robot field geologist pulled out her rock abrasion tool (RAT) and performed a six-position -- daisy -- brush mosaic on Route 66. The rover then analyzed the area with the microscopic imager (MI) and placed her Mössbauer spectrometer on the rock for an extended observation.

That afternoon, Spirit took some images of rocks dubbed Back Lot and Cameo with her PanCam and mini-TES. Later, during the Martian night, the rover retracted her Mössbauer spectrometer, and placed her APXS on Route 66 for an integration that would continue until morning.

On Thursday - Sol 100, Spirit stored her APXS, stowed her IDD, and backed up from Route 66 in preparation for an afternoon drive testing. It was her first chance to test some of the new mobility enhancements she'd just received in the new flight software. Before taking off, though, the rover used her mini-TES to examine a the daisy patch of Route 66's surface she had scrubbed the day before.

Then, in the early Martian afternoon, Spirit took off on a 210-foot [64-meter] drive, her longest one-sol drive so far. The final 78.7 feet [24 meters] of the drive were navigated with the enhanced autonomous navigation capabilities. After her traverse, the rover completed post-drive imaging and used her mini-TES on sky and ground targets. With 100 sols under her belt and .44 miles [706.5 meters] on her odometer, Spirit went to sleep for the night.

On Friday - Sol 101, Spirit continued on her journey to the Columbia Hills, roving along conducting remote science here and there.

OPPORTUNITY FROM MERIDIANI PLANUM
Sols 76 - 82

Opportunity took a break from examining the trench she dug at the Anatolia fracture site region a week ago Thursday, and her controllers put her into stand-down mode to begin receiving her new flight software uploads that Friday. On Tuesday - Sol 78, she rebooted into the new program.

While Opportunity was receiving her new flight software, her Mössbauer spectrometer was analyzing some of the soil tailings at the end of the trench and her APXS instrument pointed up into the atmosphere to collect some atmosphere measurements.

Meanwhile, down on the ground, science team members were busy analyzing the data Opportunity had returned from Bounce Rock, the "different" looking, football-sized, rock on the plains of Meridiani Planum that the rover just happened to hit while bouncing to a stop inside protective airbags on landing day. Intriguingly, they have discovered that Bounce Rock has a composition unlike anything seen on Mars before, but a lot like something Martian here on Earth - meteorites that were ejected from the Red Planet years ago.

The MER scientists described two such meteorites during the news conference. One rock to which Bounce Rock appears compositionally similar is named Shergotty. Found in India in 1865, Shergotty gave its name to a class of meteorites called shergottites. The other is the shergottite EETA79001 - the only meteorite to feature two compositionally different rocks melded into one unit, which was found laying out on the ice in Antarctica in 1979. [These two meteorites and about 18 other meteorites found on Earth are believed to have been ejected from Mars by the impacts of large asteroids or comets hitting Mars.]

"With the APXS instrument, we have been routinely analyzing 16 different elements in the soils and rocks as we've progressed during the mission, and this gives us a very good fingerprint of materials which we can then take and compare with a database we have that covers literally thousands of rocks and soils and then see what it may match up to," explained science team member Benton Clark of Lockheed Martin Space Systems.

In these comparison studies, Clark and colleagues found that Bounce Rock is strikingly similar compositionally to EETA79001-B. "This meteorite very interestingly has two different sets of rocks in it -- so there's an A part and a B part," Clark informed. Although the A part "does not match Bounce Rock well at all," he said, the A part is a really good match. "We have really good fingerprinting capabilities, and now we think we have a rock that is close and may be almost identical to something we have here on Earth and know a lot about, and, as I was mentioning to some of the team today, [we now] almost have a built-in calibration standard on Mars to test all the instruments against."

The resemblance also helps resolve a paradox about the meteorites. Bubbles of gas trapped in them match the recipe of Martian atmosphere so closely that scientists have been confident for years that these rocks originated from Mars. But examination of rocks on Mars with orbiters and surface missions had never found anything like them, until now.

Christian Schroeder, a rover science-team collaborator from the University of Mainz, Germany, which supplied both Mars rovers' Mössbauer spectrometer, used for identifying iron-bearing minerals reported that he and his team have also found a "striking similarity in Mössbauer spectra" of Bounce Rock and Shergotty.

"Concluding from these observations, we think this rock did not originate on the Meridiani plains, because it is not oxidized as the surrounding and it shows a different mineral signature," said Schroeder. "It might have been carried there by an impact event." He is far from alone in his thinking.

Opportunity's mini-TES data indicate that the main ingredient in Bounce Rock is a volcanic mineral called pyroxene, according to science-team collaborator Deanne Rogers of Arizona State University. It's a finding that is corroborated by data from the Mössbauer spectrometer. The high proportion of pyroxene makes it unlike not only any other rock studied by Opportunity or Spirit, but also unlike the volcanic deposits mapped extensively around Mars by the thermal emission spectrometer (TES) onboard the Mars Global Surveyor (MGS) orbiter, she noted.

"Global mapping with the TES has revealed that Mars is largely dominated by a rock called basalt, which has much more plagioclase, and less pyroxene that what we're seeing in Bounce Rock at Opportunity," Rogers elaborated. The rocks being analyzed at the Gusev Crater site, on the other hand, "are very similar to the global basalt."

For all their similarities, there are mineralogical differences between Bounce Rock and EETA79001, Rogers continued. And those differences are "important" and "indicate that they probably did not come from the same impact event but perhaps had similar formation conditions or sources."

So where might Bounce Rock have come from?

The MER team was wondering the same thing, Rogers said, as she presented a series of mosaiced images from the thermal emission imaging system currently orbiting on Mars Odyssey. The thermal imager measures temperature of course and at night rocks are warmer than their surroundings. "So you can use these nighttime images as rock abundance maps and where you see brighter spots, you see rock material," she explained.

Indeed, the images suggest a possible origin for Bounce Rock. About 31 miles [50 kilometers] southwest of Opportunity's landing location lies an impact crater that is about 16 miles [about 25 kilometers] in diameter. The images reveal that some rocks thrown outward by the impact that formed that crater flew as far as the distance to the rover. "So some of us think that perhaps Bounce Rock could have been ejected from this crater to the south of us," Rogers said.

The different instruments that can analyze rocks and soils on these MER missions have turned out to be of "great value," said Clark, " because each of us is getting a somewhat different perspective and adding more to solve the mystery of what we're finding here." It's a mystery they are confident they can solve.

On Tuesday - Sol 78, Opportunity took daytime readings with her Mössbauer spectrometer on Jeff's Choice, a soil target in the tailings of the trench she dug at Anatolia on Sol 73.

The rover began her first full day operating with her new flight software on Wednesday, performing a free-air integration with her APXS, a procedure that measures the effect of the Mössbauer spectrometer's radiation source on the APXS' sensor, allowing science team members to subtract out the Mössbauer spectrometer 'influence' for an accurate calibration.

Opportunity spent Thursday - Sol 80 examining the Anatolia trench, taking close-up pictures with her MI of the soil and tailings targets called Jeff's Choice, RipX, Jack Russell, Beagle Burrow, and NewRipX. The rover also used her navigation camera (NavCam) and her PanCam to take pictures in the drive direction toward Endurance Crater, her spectrometers to gather data at several of the soil targets, and her mini-TES and Pan Cam to collect some more atmospheric data.

The robot field geologist awoke on Friday with her APXS still on the soil target Beagle Burrow from an integration she began earlier during the Martian night. She stowed her IDD, then backed up to image the trench in Anatolia before heading out toward her next chosen destination, Fram Crater.

After completing a 24.6-foot [7.5-meter] drive, Opportunity stopped at a trough to image a rock outcrop within it with her PanCam. After a bit of guided driving, the rover then set out once again, this time using her autonomous navigation. She traveled more than another 100 feet, bringing her day's drive distance up to 131 feet [more than 40 meters]. Nearly reaching the second of four waypoints on the way to Fram Crater, the rover imaged her new surroundings to identify any future driving hazards. An afternoon nap preceded the sol's final science session, atmospheric observations with the mini-TES and PanCam.

Today - Sol 82, Opportunity took some morning atmospheric observations and a quick look back at where she's been with her PanCam. Then, just three days after switching to the new flight new software, the rover shattered the record for a single day's driving on Mars, covering 462 feet [140.9 meters]. That is about 40 meters farther than either the best previous one-day drive, by Opportunity two weeks ago, or the total distance trekked by the smaller Sojourner rover during her entire three-month mission in 1997.

The first 180 feet [55 meters] was done as a 'blind' guided drive based on previously acquired images. Speed during that session averaged 394 feet [120 meters] per hour. For the rest of the traverse, Opportunity used autonomous navigation, watching for obstacles, choosing her own path, and averaging 131 feet [40 meters] per hour. After the drive, the rover took forward-looking images for planning the next drive.

Opportunity's record-setting drive took three hours -- a good time for a marathon -- and brought the rover to within 295 feet [about 90 meters] of Fram Crater. It also took her over the 600-meter threshold, a criterion that had been set for at least one of the Mars Exploration Rovers to achieve in order for the mission to be called a complete success. Opportunity has now traveled a total of .39 mile [627.7 meters], catching up with Spirit who crossed that 600-meter threshold two weeks ago.

Tomorrow, Opportunity is scheduled to take in a true Sunday drive, roving ever closer to Endurance Crater.

To be continued. . . . next week.
 
See other posts from April 2004

 

Or read more blog entries about: Opportunity, Spirit, mission status, Mars Exploration Rovers

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