Sunday Drive, Adirondacks
Pasadena, Sol 15
On Mars Sunday, the 15th martian day, or sol, of Spirit’s journey, images taken by the panoramic camera onboard the Mars Exploration Rover showed "Adirondack," the rover’s first target rock.
|Spirit’s first rock target, as visualized with virtual reality software and actual image data inputs
Spirit traversed the sandy martian terrain at Gusev Crater to arrive in front of the football-sized rock on Sunday, Jan. 18, 2004, just two days after it successfully rolled off the lander. The rock was selected as Spirit’s first target because its dust-free, flat surface is ideally suited for grinding. Clean surfaces also are better for examining a rock’s top coating.
Scientists named the angular rock after the Adirondack mountain range in New York. The word Adirondack is Native American and is interpreted by some to mean "They of the great rocks."
On its first post-egress drive on Mars Sunday, engineers drove Spirit approximately 3 meters (10 feet) toward this first rock target, a football-sized, mountain-shaped rock. The drive took approximately 30 minutes to complete, including time stopped to take images. Spirit first made a series of arcing turns totaling approximately 1 meter (3 feet). It then turned in place and made a series of short, straightforward movements totaling approximately 2 meters (6.5 feet). The distance from Columbia Memorial Station toward the first rock target, seen in the foreground, was carefully traversed. The football-sized rock was dubbed Adirondack because of its mountain-shaped appearance.
Scientists plan to use instruments at the end of the rover’s robotic arm to examine the rock and understand how it formed. The tool-carrying arm is called the Instrument Deployment Device (IDD) because it houses four diagnostic instruments used to answer question about Mars’ water history.
The arm has a rotating head or ‘turret’, that can place various instruments into action against a rock, soil, or boulder: the Microscopic Imager, Mossbauer, Alpha Proton X-ray Spectrometer (APXS), and the Rock Abrasion Tool (RAT).
"Cutting into the rock beyond the weathered surface rind will reveal a flat cross section of fresh rock," says Stephen Gorevan, co-Investigator for the Athena Science Payload. Gorevan is chairman of Honeybee Robotics, in New York, which designed and built the RAT–an abrasive drill-like fan that cleans dust from the surface and eventually will be used to probe inside the kinds of rocks that will be driven towards in future targets. The RAT works somewhat like a surface grinder, the sort a machinist might use to clean or shape a metal surface. But, Gorevan says, "the RAT must cut strong rock with much less force than a typical person would exert with a hand held grinder." "The RAT needed to be specially designed to execute low-force cutting."
To test and drive the rover, visualization software is used by engineers. The software simulates the rover’s movements across the martian terrain, helping to plot a safe course. The virtual 3-D world around the rover is built from actual images taken by Spirit’s stereo navigation cameras.
Scientists are eager to begin examining the rocks because, unlike soil, these "little time capsules" hold memories of the ancient processes that formed them. Data from the camera’s red, green and blue filters were combined to create this true color picture.
Two other rocks nearby, called "Sashimi" and "Sushi", were rocks that scientists considered investigating first. Ultimately, these rocks were not chosen because their rough and dusty surfaces were ill-suited for grinding. Dusty surfaces also can obscure observations of a rock’s top coating.
|The twin "Sashimi" and "Sushi" rocks that missed the first cut, owing to their dusty covering. Credit: NASA/JPL|
While one engineering and operations team is driving on Mars, another one is guiding the next incoming rover.
Eight Million Miles to Go, Coming in Fast
For what mission planners expect to be the last major trajectory correction maneuver, the second Mars Exploration Rover, Opportunity, received commands from Earth on January 16, at 6 p.m. PST to fire thrusters in a sequence carefully calculated by the mission’s navigators. The spacecraft is spinning at two rotations per minute. The maneuver began with a 20-second burn in the direction of the axis of rotation, then included two 5-second pulses perpendicular to that axis.
"Looks like we got a nice burn out of Opportunity," said JPL’s Jim Erickson, mission manager. "We’re on target for our date on the plains of Meridiani next Saturday with a healthy spacecraft."
Before the thruster firings, Opportunity was headed for a landing about 384 kilometers (239 miles) west and south of the intended landing site, said JPL’s Christopher Potts, deputy navigation team chief for the Mars Exploration Rover Project. The maneuver was designed to put it on course for the target.
In addition to the "big science weekend", Dr. Joy Crisp said preparations are busily proceeding for the Opportunity rover’s descent in 8 days. The planned trajectory correction gives Opportunity "a predicted 80 miles by 7 mile landing ellipse", on the other side of Mars, a target pointing to a grey, basaltic plain called Terra Meridiani. "There is little chance that we will do further maneuvers as things are looking good."
Opportunity’s schedule still includes two more possible trajectory correction maneuvers, on Jan. 22 and Jan. 24, but the maneuvers will only be commanded if needed. As of 5 a.m. Sunday, PST, Opportunity had traveled 444 million kilometers (276 million miles) since its July 7 launch, and will have 12.5 million kilometers (7.8 million miles) left to go.