Opportunity Knocks, Spirit Responds
Summary (Jan 29, 2004): Getting the first picture back in a week from Spirit has the rover team hopeful that the problems with software resets and a lack of commandability may have stemmed from too many files on board the spacecraft.
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When Opportunity Knocks, Spirit Responds
NASA's Mars Exploration Rover Spirit took and returned this image on January 28, 2004, the first picture from Spirit since problems with communications began a week earlier (Sol 18). The image from the rover's front hazard identification camera shows the robotic arm extended to the rock called Adirondack.
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Spirit's Sol 25 image of its Instrument Deployment Device
Credit:NASA/JPL |
As it had been instructed a week earlier, the
Mössbauer spectrometer , an instrument for identifying the minerals in rocks and soils, is still placed against the rock. The tool is used for identifying the types of iron-bearing minerals in rocks and soilEngineers are working to restore Spirit to working order so that the rover can resume the scientific exploration of its landing area.
The spectrometer is shown on the turret of the rover's robotic arm called the Instrument Deployment Device (IDD). While this instrument had nothing to do with the current engineering communication issues, it is one of the diagnostics that can run for days unattended. A twenty hour spectrometer reading, for instance, was initially planned to occupy Spirit's timeline, while Opportunity was traveling through its challenging entry to landing phase. The Mössbauer instruments on both rovers however have required some workarounds since August, about one month after launch.
First, Spirit's Mössbauer spectrometer returned data that did not fit expectations during its first in-flight checkup months ago. A drive system that rapidly vibrates a gamma-ray source back and forth inside the instrument appeared to show partial restriction in its motion.
"The drive system is adjustable. We can change its velocity. We can change its frequency," said Dr. Steve Squyres of
Cornell University, Ithaca, N.Y., principal investigator for the rovers' science instruments. "We've found a set of parameters that will give us good Mössbauer science if the instrument behaves on Mars the way it is behaving now."
The corrective countermeasures include using a higher frequency of back-and-forth motion. "With these settings, whatever happened during launch will not decrease the quality of the data we get from the instrument," said Dr. Göstar Klingelhöfer, of Johannes Gutenberg University, Mainz, Germany, lead scientist for the Mössbauer spectrometers on both rovers. "The instrument was designed with enough margin in its performance that we can make this change with no significant science impact."
Another fact that has emerged from the in-flight checkouts of the Mössbauer spectrometers on both spacecraft is that the internal calibration channel of the Mössbauer spectrometer on Opportunity is not functioning properly. But because the instrument has the redundancy of a separate, completely independent external calibration method, this problem will not hamper use of that instrument, Squyres said.
For Opportunity, it is the 5th martian day since landing, or Sol 5. For Spirit, it is Sol 26. Since their eighteenth martian day, Spirit scientists have been catching up with the wealth of pictures and chemical spectra that are still just a fraction of the mission analysis they ultimately hope to return from Mars. The prevailing theory as to why the Spirit rover has taken a scientific pause may even have something to do with this early haul of data: too many files have accumulated in the rover's flash memory for proper commandability.
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Montage of soil textures, Moon, Venus, Mars multi-sites
Credit:NASA/JPL |
"The [robotic] arm is exactly where we expected," said Jennifer Trosper, mission manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. It is still extended in the same position as when the rover developed communication and computer problems on Jan. 22.
Engineers are sending commands today for the rover to begin making new scientific observations again, starting with panoramic camera images of nearby rocks. Today's commands also tell the rover to send data stored by two instruments since they took readings on Adirondack last week -- the Mossbauer spectrometer and the alpha particle X-ray spectrometer, which identifies the chemical elements in a target.
"We know we still have some engineering work to do, but we think we understand the problem well enough to do science in parallel with that work," Trosper said. Several attempts to get a full trace of data related to the rover's problem have only partially succeeded. The engineers might choose to reformat the rover's flash memory in the next few days.
A health check of Spirit's camera mast is on the agenda for today. Another health check, of an actuator motor for a periscope mirror of the miniature thermal emission spectrometer, is planned for Friday.
Halfway around Mars from Spirit, Opportunity's lander platform successfully tilted itself forward by pulling airbag material under the rear portion of the lander then flexing its rear petal downward. "What this did is drive our front edge lower," said JPL's Matt Wallace, mission manager. "The tips of the egress aid (a reinforced fabric ramp) are now in the soil. That makes egress look perfect. It's going to be an easy ride." The rover also retracted a lift mechanism underneath the rover, to get it out of the way for the egress, or drive-off.
During Opportunity's sol 6, the martian day that started today at 10:26 a.m. PST, the rover will be commanded to lower the middle pair of its six wheels and to release its robotic arm from the latch that has held it since before launch.
Yesterday, Opportunity used its miniature thermal emission spectrometer on a portion of the landing neighborhood that includes a rock outcrop. The instrument identifies the composition of rocks and soils from a distance.
Related Web Pages
Mars Exploration RoversSpirit Condition Serious Water SignsMicroscopic ImagerGusev Crater Pancam- Surveying the Martian Scene
Mössbauer spectrometer Alpha Proton X-ray Spectrometer Mars Rover: The Owner's ManualNote:
Missions
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Thursday, January 29, 2004
