It's been a while since I posted on the Mars missions. That's not because I haven't been keeping up or lost interest, I've just been really busy with Mozilla and Firefox-related work. It seems like months since my last posting so here's a quick update. (caution: most links here are to large photographs so you might want to open them in background tabs or skip them if you don't have a serious internet connection.)
Spirit, 185 sols into her journey, with over 2 miles on the odometer and continuing the climb up the Columbia Hills at Gusev Crater, underwent a late July "tune-up". The tune-up included an attempt to lubricate her right front wheel's drive motor (which was drawing considerably more power than the other wheels,) and re-calibrate the front hazard avoidance model to help Spirit hit targets more accurately with the tools on her robotic arm. The tune-up for the robotic arm was a complete success, but the right front wheel lubrication was only a partial success and engineers decided to move to a new driving mode which has Spirit driving in reverse and dragging the ailing wheel when its use isn't critical. They hope this will extend the lifetime of the wheel as Spirit continues her trek up the hills looking for interesting rocks to study.
Heading into the Martian winter, power is becoming one of the primary issues of day to day maneuvering and science. With the sun getting lower in the skies, Spirit gets less and less charge on her batteries and positioning and tilt of the rover is crucial to getting the most out of the sun's weakened rays. "If Spirit parks with a northerly tilt, the rover will see between 350 and 380 watt-hours of energy, but if Spirit stops on flat ground or with a southerly tilt, solar energy is as low as 280 watt-hours. So engineers make a concerted effort to find the north-facing islands along Spirit's path."
By mid-August, Spirit had climbed to an elevation of roughly 120 feet (above the landing site at the floor of Gusev Crater,) to the target rock dubbed "Clovis". Spirit used the "rock abrasion tool, microscopic imager, alpha particle X-ray spectrometer, and Mössbauer spectrometer to probe deeper into the history of this rock. Clovis is the most altered rock encountered by Spirit to date." Along with several days of amazing science work, Spirit continued to take Pancam photos for a large color mosaic (low res version) from this great viewing location.
Spirit continues her journey up the hills with more than 2.24 miles on the odometer with little or no slowdown in science gathering, driving, and taking great photographs (It's nice to compare the journey map above with the rover trails on the right hand side of this image. gives you a great perspective on Spirit's trek.)
On the opposite side of the planet, Opportunity also engaged in some "tune-up" and testing activities including similar robotic arm calibrations, investigation into some problems with the door on the alpha particle X-ray spectrometer, and experimentations in taking photos while sending UHF data. Everything is in working order and with about 0.9 miles on the odometer, Opportunity continues her investigating descent into Endurance Crater.
On July 30th, Opportunity worked her 180th sol on Mars, twice the mission nominal lifetime. Slippage is one of the major concerns as Opportunity descends into the crater. The rocky surface varies in composition with some areas of the "pavement" providing great traction and other sand covered areas causing the rover to experience as much as 50% slippage. The rover team spends quite a bit of time calculating and compensating for this slippage. It seems like they're starting to get a good "feel" for the surfaces and the rover's interaction with those surfaces, hitting targets with increasing precision. Early August experiments in traction strengthened the rover team's confidence that Opportunity would be able to climb back out of the crater at a later date.
In addition to the mobility tests, the team also attempted a very cool turn in place maneuver during communications with Odyssey to try to "keep Odyssey in the sweet spot of the rover's ultra-high-frequency antenna pattern as the orbiter swept across the sky. The total data return was about 135 megabits." This was about 20 megabits better than they could have pushed up had the rover just sat in place. These kind of experiments provide great data for this and future missions.
Opportunity continues to conduct great science investigation with all of her toolkit intact and functioning (though not without glitches). The rover team is currently in "restricted planning" mode. This restricted planning "happens when the timing of the rover's sol on Mars and our day in the California time zone get out of sync due to the nearly 40-minute difference in length of Earth days and Mars sols". During this period, things move a bit slower because rover mobility (wheels and arm) is limited to every other day. On non-moving days, the "restricted" activities include remote sensing (like these beautiful cloud images) that doesn't require knowledge of the current position of the rover or the robotic arm, things like imaging, self-diagnostics, and data relaying.
Earth and Mars are quickly approaching conjunction and that means limited or no radio communication for several days. The rover teams have planned to pad this few days and will stop sending daily instructions to the rovers for nearly two weeks starting on September 8th for Spirit and September 9th for Opportunity. During that time, the rovers will continue to perform Mössbauer integrations and atmospheric analysis but won't be making any wheel or arm movements (I'm sure the scientists will appreciate a few days off :-). Normal operations will resume on September 20th. I'll try to get back into more regular updates after that.
update: If you can't wait for me to update, or even if you can, you really should keep an eye on Martian Soil, The Eternal Golden Braid, or if you're interested in more than Mars, check out Lunar Soil :-)
