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PASSPORT TO KNOWLEDGE - To MARS with MER
When the going gets tough, the tough get going.
When the going gets tough, the tough get going. That's what's happening now at NASA JPL: as if landing a second spacecraft, Opportunity, on Mars were not difficult enough, the Mars Exploration Rover team is experiencing serious difficulties with Spirit, already on the ground at Gusev Crater. Spirit was going to be given a planned rest during Opportunity's landing and first days on the surface -- though this kind of spell of "intensive care" was in no-one's play book -- in order to allow full attention to today's inherently risky events. But the Jan 23 briefing was evidence of the quality and commitment of the mission team: project manager, Pete Theisinger, was calm and forthcoming: yes, there were serious communications and possibly hardware problems with the spacecraft (see JPL releases linked in below) but a dedicated team of engineers was carefully working through data to come up with answers, while a separate team was attending to the Entry, Descent and Landing, or EDL, of Opportunity (set for the evening of Saturday Jan 24, Pacific time.) Most of the questions, naturally, were about Spirit, which unfortunately eclipsed the amazing information and images in the reports of Wayne Lee, Miguel San Martin and Adam Steltzner: for the past few weeks, they and colleagues have been working on a "reconstruction" of Spirit's EDL, in order to fine tune that for Opportunity. They've been able to get to incredible detail, including data that the Descent Rate Limiter (controlling the unspooling of the bridle linking the lander to the backshell) took 11 not the expected 6 seconds to deploy. Their information about the number and direction of the bounces also allowed them to determine exactly where Spirit came to rest: equally astonishing images from the Mars Orbital Camera aboard the Global Surveyor allowed MOC camera PI, Mike Malin, to show where the parachute and backshell, the heat shield, and Spirit herself came to rest. Check out the images for evidence of how powerful the combination of software, hardware and human ingenuity can be. Spirit's communications difficulties are serious and as yet mysterious: not even Pete Theisinger could predict if and when progress might be made. But the Rover mission team are tough and dedicated: if anyone can figure out the problems and fix them, it's them. Stay tuned for news from Opportunity and soon, we hope, once more from Spirit.
Spirit Condition Upgraded as Twin Rover Nears Mars
January 24, 2004
Hours before NASA's Opportunity rover will reach Mars, engineers have found a way to communicate reliably with its twin, Spirit, and to get Spirit's computer out of a cycle of rebooting many times a day.
Spirit's responses to commands sent this morning confirm a theory developed overnight that the problem is related to the rover's two "flash" memories or software controlling those memories.
Image Credit: NASA/JPL/Cornell University
"The rover has been upgraded from critical to serious," said Mars Exploration Rover Project Manager Peter Theisinger at NASA's Jet Propulsion Laboratory, Pasadena, Calif. Significant work is still ahead for restoring Spirit, he predicted.
Opportunity is on course for landing in the Meridiani Planum region of Mars. The center of an ellipse covering the area where the spacecraft has a 99 percent chance of landing is just 11 kilometers (7 miles) from the target point. That point was selected months ago. Mission managers chose not to use an option for making a final adjustment to the flight path. Previously, the third and fifth out of five scheduled maneuvers were skipped as unnecessary. " We managed to target Opportunity to the desired atmospheric entry point, which will bring us to the target landing site, in only three maneuvers," said JPL's Dr. Louis D'Amario, navigation team chief for the rovers.
Opportunity will reach Mars at 05:05 Sunday, Universal Time (12:05 a.m. Sunday EST or 9:05 p.m. Saturday PST).
From the time Opportunity hits the top of Mars’ atmosphere at about 5.4 kilometers per second (12,000 miles per hour) to the time it hits the surface 6 minutes later, then bounces, the rover will be going through the riskiest part of its mission. Based on analysis of Spirit's descent and on weather reports about the atmosphere above Meridiani Planum, mission controllers have decided to program Opportunity to open its parachute slightly earlier than Spirit did.
Mars is more than 10 percent farther from Earth than it was when Spirit landed. That means radio signals from Opportunity during its descent and after rolling to a stop have a lower chance of being detected on Earth. About four hours after the landing, news from the spacecraft may arrive by relay from NASA's Mars Odyssey orbiter. However, that will depend on Opportunity finishing critical activities, such as opening the lander petals and unfolding the rover's solar panels, before Odyssey flies overhead.
Spirit has 256 megabytes of flash memory, a type commonly used on gear such as digital cameras for holding data even when the power is off. Engineers confirmed this morning that Spirit's recent symptoms are related to the flash memory when they commanded the rover to boot up and utilize its random-access memory instead of flash memory. The rover then obeyed commands about communicating and going into sleep mode. Spirit communicated successfully at 120 bits per second for nearly an hour.
"We have a vehicle that is stable in power and thermal, and we have a working hypothesis we have confirmed," Theisinger said. By commanding Spirit each morning into a mode that avoids using flash memory, engineers plan to get it to communicate at a higher data rate, to diagnose the root cause of the problem and develop ways to restore as much functioning as possible.
The work on restoring Spirit is not expected to slow the steps in getting Opportunity ready to roll off its lander platform if Opportunity lands safely. For Spirit, those steps took 12 days.
The rovers' main task is to explore their landing sites for evidence in the rocks and soil about whether the sites' past environments were ever watery and possibly suitable for sustaining life.
JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Office of Space Science, Washington. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu.
