14 DAY TRIAL // Following a new series of test drives of the Martian rover Spirit, scientists at the NASA Jet Propulsion Laboratory (JPL), who manage the MER mission, say that the robot's rear right wheel is still jammed, and that the machine is in serious danger of being left with just four operational wheels of its original six. The latest diagnostics tests were conducted on Sol 2109 (December 8), and results are just in. Experts managing the resilient exploration rover say that they will continue to assess its integrity in future tests over the coming weeks.
The rover has been stuck in a patch of loose Martian soil named Troy since late April, having breached a thin, solid crust. Its wheels are now embedded up to their hubcaps inside the powder-like dust. Scientists at the California Institute of Technology (Caltech)-based JPL have been working on finding a way of freeing Spirit for many months, by employing a test rover, similar to the one on Mars, placed inside a sandbox mimicking Troy. Actual drives began a short while ago, but stalls on the machine's rear right wheels have halted attempts, after initial tests suggested some progress was being made.
“The Sol 2109 plan included a check of the grind motor of Spirit's rock abrasion tool (RAT) because it shares the same motor controller as the right-rear wheel. It also included rotor resistance tests on the right-rear motor at three temperatures using opposite voltage polarity from earlier tests, backward and forward commanded motion of the right-rear wheel, and a check of rotor resistance on all other operating wheels,” JPL engineers announced in an official statement on their website.
“The right-rear wheel rotor resistance tests continue to show very elevated resistance, although not as high as in previous tests, and exhibiting a curious voltage-dependent effect. No motion of the right-rear wheel occurred during the backward commanded motion. The forward motion was not executed since the initial backward motion did not occur. The rotor resistances on all the other operating wheels are nominal,” they added.
Plans are now to continue with the diagnostics tests, until all possible internal issues related to the jam are exhaustively researched. After that time, the team will focus on looking for external obstacles that may be preventing the wheel from moving. The group is also preparing for the worst, creating scenarios to see if the rover could hypothetically be moved with just four operational wheels. Everything must be done in a hurry, though, as the winter solstice (May 13, 2010) approaches. The current position Spirit has will most likely not allow it to survive another winter, so efforts to extricate it are on a deadline.
To make matters even worse, the robot was recently discovered to be perched atop a crater, with its wheels sitting astride the rim. “By being stuck at Troy, Spirit has been able to teach us about the modern water cycle on Mars. We’ve sat here for more than 6 months. That’s a long time to take measurements. We’ve learned a lot. Troy is a good place to be under siege, but we’re ready to leave,” Washington University in St. Louis (WUSL) expert Ray Arvidson said recently.