OPPORTUNITY UPDATE: Opportunity Reverses Path - sol 1498-1504, April 10-17, 2008:
During the past week, Opportunity celebrated another major milestone by reaching 1,500 sols (Martian days) of continuous exploration of the red planet!
Meanwhile, Opportunity continued to execute a “toe dip” stategy of driving forward a short distance and backing up again to characterize the sandy terrain beneath the rover’s wheels. While driving toward the promontory known as “Cape Verde” in the rim of “Victoria Crater,” Opportunity experienced wheel slippage of more than 90 percent. The rover also experienced high tilt during the backward part of the drive. Following a series of adjustments to both slippage and tilt limits, Opportunity’s front wheels had begun to dig into the terrain. At that point, the rover’s handlers decided to concentrate on driving backward to extract the rover’s front wheels and prevent them from digging further into the sand. Making slow and steady progress, as of sol 1502 (April 15, 2008), Opportunity had driven backward 24 centimeters (9.5 inches) with no errors, giving rover drivers hope that the rover would soon be out of the sand.
Opportunity’s handlers implemented a “Stow/Go/Unstow” strategy of unstowing the robotic arm after each day’s drive to avoid having the arm in the stow position during thermal cycling (overnight temperature changes). This freed the arm for full use of its scientific tools in the event of a cold-induced motor failure. On sol 1502 (April 15, 2008), while attempting to unstow the arm, Opportunity experienced a stall in the joint that controls shoulder position. The nature of the stall appeared to be different from previous stalls in the same joint (known as Joint 1). On sol 1504 (April 17, 2008), the rover’s handlers directed Opportunity to run a diagnostic test of movement in the robotic arm. While moving the joint, Opportunity experienced another stall. Investigation of this anomaly is expected to continue for the remainder of this week.
Opportunity is healthy and all subsystems are performing as expected, with the exception of the investigation of the robotic arm. Immediate plans call for continued focus on getting out of the sand and resolving the robotic-arm anomaly.
In addition to receiving morning instructions directly from Earth via the rover’s high-gain antenna, sending data back to Earth via the UHF antenna on the Mars Odyssey orbiter, and measuring atmospheric dust with the panoramic camera, Opportunity completed the following activities:
Sol 1498 (April 10, 2008): Opportunity surveyed the horizon and the sky and measured atmospheric dust at sunset with the panoramic camera. After transmitting data to Odyssey, the rover measured atmospheric argon with the alpha-particle X-ray spectrometer.
Sol 1499: In the early part of the sol, Opportunity took thumbnail images of the sky with the panoramic camera and shot a 4-frame movie of potential clouds with the navigation camera. The rover stowed the robotic arm, drove toward Cape Verde, acquired post-drive images with the hazard-avoidance cameras, and unstowed the robotic arm.
Sol 1500: Opportunity acquired a full-color, 2-by-1 panel of images of Cape Verde using all 13 filters of the panoramic camera.
Sol 1501: Opportunity recharged the battery.
Sol 1502: Opportunity started the day by monitoring dust on the panoramic-camera mast assembly and measuring atmospheric dust. The rover stowed the robotic arm, drove toward Cape Verde, acquired images of the wheel cleats in the rover’s tracks to assess traction and other post-drive images with the hazard-avoidance cameras. Opportunity unstowed the robotic arm before sending data to Odyssey and going to sleep.
Sol 1503: In the morning, Opportunity surveyed the horizon with the panoramic camera. The rover acquired microscopic images of the robotic arm to document changes during the diagnostic test of the arm’s ability to move.
Sol 1504 (April 17, 2008): In the morning, Opportunity acquired full-color images, using all 13 filters of the panoramic camera, of trenches created by the rover’s wheels that have been informally named “Williams” and “Harland.” The rover took spot images of the sky for calibration purposes with the panoramic camera and ran more diagnostic tests of the robotic arm. Opportunity took thumbnail images of the sky with the panoramic camera. After relaying data to Odyssey, the rover used the alpha-particle X-ray spectrometer to measure argon gas in the atmosphere. Plans for the next morning called for the rover to take more thumbnail images of the sky with the panoramic camera.
As of sol 1502 (April 15, 2008), Opportunity’s total odometry was 11,691.49 meters (7.26 miles).