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| An image from the Spirit rover's rear hazard identificarion camera shows the landing platform, now about one meter (about three feet behind it. Below, the same image in 3D Click on the images for high-resolution versions (1024 x 1024 pixels, 100K) |
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The signal to roll down the ramp was sent from Mission Control at JPL at 12:21 a.m. Pacific time. At 1:53 a.m. JPL received word back from the rover that it was on the surface of Mars. The successful rolloff was a particular triumph for Cornell astronomy professor Steven Squyres, leader of the rover science program, who has been working towards this goal for the past 15 years. "This is a night extraordinarily rich in its significance," he said.
Engineers at JPL played the pop tune "Who Let the Dogs Out" by the Baha Men as the first data from Spirit began to come in from NASA's Deep Space Network.
Elachi and his mission team later appeared at 3 a.m. Pacific time news conference so jammed with cheering, applauding JPL employees that there was standing room only. Mission manager Jennifer Trosper uncorked a bottle of champagne for her colleagues, including Kevin Burke, lead mechanical engineer for the drive-off. "There was a great sigh of relief from me," said Burke. "We are now on the surface of Mars."
After a slow and cautious two-day, 115-degree swivel-in-place on its triangular landing platform, putting the rover in a north-northwest-facing direction, the golf cart-size vehicle slowly crept down one of the lander's stretch-fabric ramps, moving 3 meters (10 feet) in 78 seconds. The back of the rover ended up about 80 centimeters (2.6 feet) away from the foot of the ramp. The rover completed the drive-off at 12:41 a.m. Pacific time.
A hazardous part of the short journey was a 4- to 6-inch drop off the edge of the ramp onto the landing site, newly named Columbia Memorial Station by NASA.
The long, tense wait between sending the rolloff command and receiving confirmation that the journey had been completed was due both to the 10 minutes it takes for data to travel one way between the two planets and to the fact that once off the rover, the vehicle had to reorient its direct-to-Earth high gain antenna. The antenna had to locate the sun in its field of view to get north so that it could then focus on the Earth. Meanwhile, the rover's software was compressing images of the rolloff from the rover's hazard-identification and navigational cameras that would slowly dribble back to Earth. The most poignant image received by JPL was a backward look at the lander, now merely space debris.
Mission planners said the rover will spend its initial hours on the surface "cleaning up" its mission sequences, or instructions, in its onboard computer. This is part of the vehicle's transition into a daily planning mode for the science part of the mission. From now on, they stressed, Squyres' science team is really in charge of the mission.
In a talk to mission managers on Wednesday night, Squyres said that although the science program will begin immediately, the rover's first foray will be "clean and straightforward and free of risk." The plan, he said, is to characterize the geological diversity of the area with the rover's suite of instruments so that scientists can "understand typical stuff" on the surface in order to provide a baseline. In about four days the rover's first targets will be rocks, then soil, he said. One rock, in particular, that has attracted his attention, he said, is pyramid-shaped with smooth facets, about 35 centimeters by 20 centimeters (14 by 8 inches), clearly shown in the rover's panoramic images.
Longer term, said Squyres, the plan is to send the rover 200 meters (220 yards) to a crater, also shown in the panoramic images, that has a diameter less than 200 meters, a rim 4 to 5 meters (12 to 15 feet) high and which probably "has been excavated down tens of meters." Squyres earlier called the crater "an extremely attractive target" because it would "provide a window to subsurface Mars." A goal of the mission is to find materials that will show if Gusev crater ever contained a lake, so finding what lies beneath the surface is considered vital.
After investigating the crater, Squyres said, the rover will "head for the hills," shown in panoramic pictures about 1 to 2 miles to the east. He noted, "The image all of us want is halfway up the hills looking back where we came from."
Initially, said science team member Ray Arvidson, some of the most exciting data will come from the robotic arm's microscopic imager, a combination of microscope and camera, that will send back a high-resolution image of an area 3 centimeters square (a little over a square inch), allowing scientists to see things "never seen before at this scale." It will show soil grain shapes and sizes and their relation to minerals, he said. Another instrument to be deployed early on, he said, will be the roc k abrasion tool, which will grind away the surface of rocks, revealing "fresh textures" underneath.
Spirit was launched from Cape Canaveral Air Force Station, Fla., on June 10, 2003. Spirit's twin rover, Opportunity, will reach Mars on Jan. 25 (Eastern time; 9:05 p.m., Jan. 24, Pacific time) to begin a similar exploration of a site on the opposite side of the planet
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