Proving Grounds: Martian Chronicles XIV
Martian Chronicles XIV
Two rovers are reaching the end of their half-year journey to Mars. Where the two NASA Mars Exploration Rovers (MER) are now can be continuously monitored in-flight. Experiments performed by the MERs will help to determine whether water might have once existed in volume on the red planet. The two Mars Exploration Rovers are targeting what imagery indicates might have been ancient dry lake beds and other geologically interesting sites in early 2004.
|Viking image of Gusev Crater, an ancient proposed lakebed that will be targeted in the forthcoming Mars Exploration Rover mission.|
The Martian Chronicles series gives an inside view of what it takes for scientists to deliver a complex mars mission. The journal entries are from Cornell’s Steve Squyres, the Principal Investigator for the Mars Exploration Rovers’ scientific package called Athena. The chronicles begin sequentially from the beginning of July 1999, four years before launch, and will culminate in the dramatic landing of the twin rovers on Mars in January 2004. The expected mission time roaming the red planet is ninety days, from January to April.
As Spirit and Opportunity speed toward Mars, more than three hundred scientists and engineers here on Earth will learn how to act in unison to master the art of commanding two very complex robots to do science on another world.
"Mars is getting pretty big in the windshield now," said Steven Squyres, Cornell professor of astronomy. He reminded Mars’ watchers that while a good landing will be important, for the scientists, research is the thing. "This is a marathon," he said.
Although the rovers’ primary mission is to search for evidence of water on Mars, Squyres cautioned that important findings are unlikely to occur immediately after landing. "The best stuff could come in February, March, April," he said. Rover Spirit, he said, will plod the Martian landscape carefully. "It doesn’t zip. It is more like a Galapagos turtle."
In late November, Squyres and his science team completed the last operations-readiness test at JPL. The team simulated five Martian days of driving a practice rover, using the vehicle’s version of a geologist’s rock hammer, the rock abrasion tool, or RAT. "We use it to remove the outer layers of a rock so that we can see what lies underneath," said Squyres in his online diary.
The team spotted a rock to study, nicknaming it Fromage, which means "cheese" in French. "Bait for the RAT, get it?" joked Squyres. "We drove the rover to Fromage, stuck out the arm, and used the RAT to grind a beautiful circular hole in it. Then we stuck [the Athena] instruments into the hole and got fantastic data. It was by far our coolest [test] yet. It was nice to finish up on such a high note."
The chronicles include an insider’s view of hardware tests and site selection to problem solving and science planning on the surface of Mars .
December 13, 2003
It’s less than three weeks until Spirit lands. Our last operations readiness test is over. The final flight software has been loaded onto both Spirit and Opportunity, and we’ve finished and tested all of the instrument commands for the first week after we land. Final pre-landing health checks are done on all the instruments. The spacecraft are ready to go.
Jamming on a Jammed Instrument
During in-flight testing of the Athena instruments aboard Spirit in August, the Mössbauer spectrometer’s drive system appeared to be jammed. Scientists and technicians from Germany and from the mission manager, the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., worked slowly and methodically to solve the problem. Squyres reported that there was a minor obstruction in the drive system, probably a bent wire.
The Mössbauer spectrometer will analyze the composition and abundance of iron-bearing minerals to gather information about early Martian environmental conditions. The instrument was provided by Germany.
"You try to design an instrument with lots of margin," said Squyres
"In other words, you try to make it better than it really needs to be. That way, if something goes wrong, it might still work okay after you make an adjustment. We did [this] on our Mössbauer, and it paid off big time," he said.
The scientists adjusted the instrument’s vibration velocity and the frequency, giving it less total motion. "While we never expected to operate the instrument with a total motion that small, we built it with enough margin that the spectrometer still will work properly on Mars," Squyres said.
Down here on Earth, we’re a little less ready. Once these things hit the ground, our whole team is going to be completely consumed by flight operations for months.
So the focus now is getting our lives in order so that we won’t have too many distractions when the time comes. Dentist appointments. Haircuts. Drivers license renewals. Flu shots. All the little things we’ve neglected for the past six months while we’ve been getting ready to land, or that we know we won’t have time for for who knows how many months after we land.
And then there’s the matter of sleep. It’s too bad we can’t save it up now, because we’re not going to be getting a lot of it after landing! But least we’re trying to make sure that everybody gets rested and healthy, so that we start off in good shape. Anyway, the plan is that in another couple of weeks the team will be as ready for all this as Spirit and Opportunity are now.
December 23, 2003
As I write this, it’s twelve days until Spirit lands at Gusev Crater. Everything is done now except the final trajectory correction maneuvers, and even those are close to being upon us.
After all these years, it’s hard to believe that we’re finally almost there. Our science payload first came together as a rough idea about a decade ago, built up from instrument concepts that had already been in work for years before that.
We began figuring out how to put it on a rover back in ’95, and we’ve been designing and building flight hardware in earnest since ’97. Starting in 2000, an army of hundreds of incredibly talented and dedicated engineers from the Jet Propulsion Laboratory and elsewhere raced to make the concept a reality in time for launch. We made it to the launch pad against some pretty long odds, and now we’re about to make it to Mars. Twice.
And there, starting on the night of January 3rd, all those years of work are going to come down to a six-minute make-or-break plunge through the martian atmosphere. Heck of a way to make a living, eh?
But I wouldn’t trade it for anything.
For the past couple of weeks, I’ve been advising my team to rest up, take it easy, spend some time with their families, and get ready for the stress and fatigue of flight operations. I’m going to take my own advice now, and make this the last web page update for the next twelve days or so.
The next time you hear from us, Spirit will be in Gusev Crater.