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A.J.S. RaylJanuary 14, 2004

Let's Roll: Spirit Poised to Cruise onto Martian Surface

Spirit is ready to roll.

After completing the last two parts of its three-part turn-in-place early this morning Pacific Standard Time (PST), the first Mars Exploration Rover stood poised to roll off the lander and take her first cruise onto the surface of the Red Planet.

"We're sitting exactly where we want to be. . . and as of now it's a 'go-poll,'" Kevin Burke, egress mechanical lead, confirmed at the morning press briefing at the Jet Propulsion Laboratory (JPL).

The first trip won't be a long one -- about 3 meters or 10 feet -- and it won't last very long -- only 75 seconds. But, in many ways, it's the most treacherous and the most important.

As JPL Flight Director Chris Lewicki has pointed out: "The most dangerous driving we'll do on the surface is the first three meters, and our own lander is the most dangerous object on the surface for Spirit right now."

Before Spirit gets her green light, however, she will spend a portion of her day --Sol 12 -- gathering some more images, specifically a few views of what is now the Columbia Memorial Station.

The initial plan for Spirit to drive straight ahead and down the front was foiled by an airbag that still hasn't completely deflated or retracted. When engineers determined that the airbag could pose a threat to the rover's rear solar panels, the "second best plan" -- to turn 115-degrees to her right and head down and out to the northwest -- was ground-truthed with models at JPL's Mars yard and set in motion.

When Spirit gets to the bottom of the ramp, her cross over onto Martian soil won't exactly be seamless. Rather, she will have to 'hop the curb,' in a manner of speaking. "We will have approximately a 10-12 centimeter [about 4 to 5 inches] drop to get onto surface," Burke explained. "But that is well within our capability. We have tested [drops] of up to the order of 57 centimeters."

Once Spirit has reached the end of her first short trek, the mission team will deploy her robotic arm to initiate her 'hands-on' three-month investigation of Gusev Crater. In other words, the robot geologist will do "what any geologist would do, reach down into the dirt and see what's there," says Deputy Principal Investigator, Ray Arvidson, of Washington University in St. Louis. Officially called the instrument deployment device or IDD, the robotic arm houses four scientific instruments: the rock abrasion tool (RAT), a microscopic imager, a Mössbauer spectrometer, and an alpha particle x-ray spectrometer (APXS).

"We should be on the surface with knowledge by sometime around 1-2 am PST -- we should get that first rear image -- and we're really looking forward to seeing that," said Burke.

That image will add to the some 4400 images Spirit has already sent home even before she rolled onto the surface -- breaking all Mars missions records for both quality and quantity of images returned within a week of arrival. But the historic moments don't stop there.

Mars Odyssey and the European Space Agency's Mars Express will fly directly over Spirit's landing site in Gusev Crater tonight and tomorrow night.

"Tonight, for first time, we're going to look up while someone else is looking down," announced Deputy Project Scientist Albert Haldemann at the morning briefing. "When Viking 1 tried to do that, there was dust storm covering the site."

Although the news didn't come as a real surprise -- NASA's two orbiters -- Mars Global Surveyor and Odyssey -- have scientific instrument on board and the MER team has been using them for their UHF communications links. "But what's interesting and what's taken a bit of planning is the collaborative and coordinated science that we can do that offers unique opportunity," explained Haldemann.

"There are things that we can do by looking in two directions at once that aren't available simply by looking down at site when lander isn't paying attention to the overflight," Haldemann continued. One significant thing they can do, of course, is get a truer picture of the atmosphere. As Odyssey flies overhead it will be taking measurements of the Martian atmosphere from above with its thermal emission spectrometer (TES), while Spirit will be turning its miniature thermal emission spectrometer or Mini-TES to look up to record the spectra.

Since Odyssey's circular orbit will bring it around to Spirit's neck of the Martian woods once every 30 days, "coordinated experiments will proceed during the MER mission," Haldemann added.

Tomorrow night -- or the day after egress, Mars Express will fly over Spirit's landing site at an altitude of about 186 miles or 300 kilometers. By comparison, the space shuttle orbits about 200 miles above the Earth. This overflight, however will be "a much rarer opportunity," Haldemann said, "because [this orbiter ]is in an elliptical orbit and very near the periapsis, the lowest approach of that orbit, and very near nadir, right over our landing site."

During the Mars Express overflight, international teams of scientists will carry out a number of coordinated observations and experiments with three instruments:

The various teams will collect and archive the data. "Then it will be on the scientists between the teams to evaluate that data in the months to come," said Haldemann. "It won't be the kind of experiment [in which] you pull out a result right away. But it allows ground truth -- information on the ground to compare to what we see from orbit, and that allows us to tie the information from orbit to the whole planet - a great value to the Mars program at NASA."

The other big events of the day came just a couple of hours after another morning briefing of "fantastic" news. At noon PST, President Bush announced his new vision for NASA, which includes sending human missions beyond Earth's orbit by 2014, returning to the Moon by 2020 then using the Moon as a launch site for missions to Mars and beyond.

Then, around 2:45 p.m., Vice-President Dick Cheney - on a combination business and campaign fundraising trip - stopped by the laboratory to take a tour and address the center's employees afterward, outside in the 'mall.' His address follows:

"The Jet Propulsion Lab has a proud history that extends back nearly seven decades. "Scientists and engineers here have made vital contributions to military aviation in World War II; developed crucial ballistic missile technology in the early days of the Cold War; launched into orbit Explorer 1, America's first satellite; and designed and deployed the Voyager spacecraft which are now both approaching our solar system's edge.

"Today, of course, you are capturing the nation's imagination with the Mars Exploration Rovers. I've just taken a tour here of the rover operations center and got a tremendous briefing, but don't worry I did not touch the controls.

"The Spirit mission is showing your ingenuity in its absolute highest form. You've landed a 5-foot-tall rover on a harsh planet over a hundred million miles away and already we are receiving pictures and data that have changed our conception of Mars. And just hours from now, the rover, built here in Pasadena, will begin moving across and through the Martian soil.

"Each of the hundreds of people here who worked on this project can be enormously proud of the mission success and you can know that people all across the country and, indeed, around the world, are thrilled and inspired by your work.

Earlier today in Washington President Bush visited NASA headquarters and outlined his vision for a second great age of space exploration. Our goals are aggressive -- to complete International Space Station by 2010, to send manned flight beyond Earth's orbit 2014, to return to moon in 2020, and to use our presence on the Moon for missions to Mars and beyond.

"These aims are ambitious. They're difficult and they're very demanding. The effort will be repaid many times over, in scientific advancement, useful new technologies, the discovery of resources on Earth and beyond, and the discovery of more about ourselves. Our continuing journeys into space will pose countless challenges, yet we will embark on these missions with confidence, because we've chosen exactly the right people to do the job. The President and I appreciate the outstanding performed by everyone here at the JPL. You're using your talent, your dedication, for the benefit of your country and of all mankind. America is proud to lead the world into space and the American people are proud of you."

Read more: Spirit, mission status, Mars Express, Mars Exploration Rovers, Mars

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Salley Rayl
A.J.S. Rayl

Contributing Editor for The Planetary Society
Read more articles by A.J.S. Rayl

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