A.J.S. RaylJan 12, 2004

Spirit Set to Roll Off Lander Thursday

Spirit is up -- standing at full height on all six wheels -- and is ready to roll off the lander heading west by northwest, probably sometime early Thursday morning Earth time, according to the latest plan.

"This leaves us set to perform egress activities," said Arthur Amador, Sol 9 mission manager said yesterday. "The rover is ready to go."

During the weekend, the mission team completed a series of engineering activities to release Spirit's mid-wheel cables and its robotic arm, which was repositioned and stowed in its 'drive' configuration. Meanwhile the 4-foot, 9-inch rover returned some 370 more megabits of data -- nearly 20 times more than Mars Pathfinder's capability. Included in those downloads are the last two octants needed to complete the color, 360-degree 'mission success' panorama.

The mid-wheel cables were the last set of cables that physically held the Mars Exploration Rover on the lander deck. A small pyrotechnic device on each side fired and cut the cable on each side. Spirit still remains attached to the lander, however, through its "umbilical cord," which, if all goes as planned, will be cut on Sol 10, or late tonight, early tomorrow morning on Earth.

Spirit and its identical twin, Opportunity -- which is still set to land at Meridiani Planum on January 24 Pacific Standard Time -- are the most complex robot explorers ever built. Spirit, for example, had to complete a complex series of commands and maneuvers just to stand. "Twelve pyrotechnic devices had to be fired, nine motorized mechanisms had to fulfill their purposes, and six structural latches had to be engaged," Chris Voorhees, a mechanical systems engineer at JPL pointed out at the daily news briefing Saturday.

The team relied on the stereo hazard avoidance cameras and numerous sensors on vehicle to determine exactly what Spirit was doing and to make sure it performed every step as it was supposed before it went on to the next. "Scores of engineers, designers, analysts, and machinists, not just at JPL, but across the country allowed Spirit to perform one of the most complex sequence of deployments ever done on a robotic spacecraft."

The mission team also spent considerable time over the weekend considering which path to take off the rover. In ground tests with rover models at the JPL 'sandbox,' the team decided against driving off down the front because of the errant airbag that has refused to fully deflate. "There is a possibility, as rover drives down, that the rear left part solar panel could brush against the airbag -- there's little bit of margin, but it's not a place we want to be," said mission manager Jennifer Trosper Saturday.

Ultimately, the team decided to turn the rover 120 degrees, "facing the right rear to where it's facing now," Trosper said, or west by northwest, and drive off that way. That direction, however coincidentally, happens to be in the direction of Sleepy Hollow, the first feature named since landing at Gusev January 3.

"We're planning to do this in three parts, so we will turn the rover 45 degrees, stop and take haz cam [hazard camera] images, [of the] lander deck and rover position," Amador explained yesterday. "Then we will move on to part 2, which will take us to about 95-degrees, and we'll do more imaging with the haz cam and make sure we're where we expected to be. Then, in part 3, we will turn the rover to 115 to 120 degrees."

The plan now is to perform the first phase on Sol 10 -- Monday night/Tuesday morning here on Earth, with the second to occur on Sol 11 -- Tuesday night/Wednesday morning, with roll off on Sol 12 - Wednesday night/Thursday morning. The mission team spent much of yesterday using the "high-fidelity model" of the rover in a dress rehearsal this roll-off at the JPL 'sandbox.'

As she stands now, Spirit is "pretty darn perfect," as Amador put it yesterday. So perfect that it provided "another dividend," pointed out JPL Science Manager John Callas.

Up to now, the science team has been devoted mostly to analyzing data coming down, but, since the telecommunications systems and linkages have been working so well, the team had the opportunity to do some "unplanned science," Callas said.

"For the first time [Saturday] night, the science team had the opportunity to plan activities for another sol, for after we egress and have six wheels on the soil," Callas said, an activity that will soon become a daily -- rather nightly -- routine.

"Our plan is day-to-day commanding -- an aggressive activity of analyzing data coming down and making decisions for what we do next, then making a detailed activity plan, and subsequently building that plan into a carefully selected set of sequences and commands." This will happen every night on Earth, during an approximate 17-hour period while the rover sleeps. "This is very, very different from missions in past where you may have known well in advance and had time to plan things in detail. With Spirit, we won't know what we're doing tomorrow until we've analyzed the data today," Callas pointed out.

Once Spirit has rolled off the lander, Callas said, "one of the first things we'll do is probably an in situ [in place] analysis where we use robotic arm to place instruments on soil in front of rover -- to make the first measurements of soil on Mars with this device." Then the team will begin its day-to-day operations of analyzing data and making decisions about what Spirit will do the next day.

"It's really a complex arduous process," Callas offered. " We have a very sophisticated, very capable rover, but it's very complex. It has to be carefully choreographed . . . there are a lot of interactions between subsystems, finite resources, and only so much power and data, and there's also {the issue of] interaction with Mars," he added.

By all accounts and evidence to date, this mission is proving to be " visually rich," as Callas noted. "We're getting tremendous amount of data [which] the science team has to simulate very quickly," he continued. "We have developed software tools that allow us to visualize in 3-D, to allow scientists to make quick, quantitative judgments about what they see and then to capture that information in a series of commands that get built and transmitted to rover. We have a very tight schedule -- if we miss an uplink for a given day then we've blown a sol." At a cost of some $4 million a day, missing a sol is "a big deal," he said. "We want to take every advantage of every daily opportunity."

At this point, all Spirit's systems appear in "good health," according to Amador. "We're getting good performance from the high gain antenna (HGA) and have had no repeats of the anomaly we experienced on Sol 2," he noted. All communication links are performing and in "excellent" working order.

Meanwhile, the entry, descent and landing (EDL) team has been analyzing the data garnered during Spirit's entry to decide whether any adjustments are necessary for Opportunity. "We were thrilled to see a good match between what Spirit measured and what we predicted," Project Scientist Joy Crisp said Saturday. "That gives us confidence that we can use same model for determining atmospheric conditions for landing at Meridiani, for the next rover landing."

Project manager Pete Theisinger announced late last Friday that the team is not going to be changing the entry flight path angle of the second Mars Exploration Rover.

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