Perseverance pays off as Mars rover's SHERLOC brought back from the brink

Bot's arm used to free instrument's dust cover and return to science

NASA engineers have performed another remarkable feat of remote debugging and restored the SHERLOC instrument of the Perseverance Mars rover to operation.

SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals) is mounted on the rover's arm and uses two cameras and a laser spectrometer to hunt for organic compounds and minerals in rocks.

Finding signs of these markers might point to evidence of past microbial life on the Red Planet. Hunting for environments that might once have been capable of supporting microbial life and looking for signatures of that life are two of Perseverance's science objectives, so a problem with SHERLOC is inconvenient despite overlap with other instruments on the rover.

The issue was not with the cameras or spectrometer but with one of the two covers designed to keep dust off the instruments' optics. Earlier this year, the cover became frozen in place. This stemmed from a malfunction in the motor that both moves the cover and adjusts the focus for the spectrometer and one of the cameras, the Autofocus and Context Imager.

Getting the dust cover to open required shaking the SHERLOC instrument. Engineers started by rotating the rover's arm before trying the percussive drill to loosen debris that could potentially jam the lens cover.

By March, although the cover had opened sufficiently to not obscure the imager, the loss of the focus motor meant that images would remain blurry. The next step was to use Perseverance's arm as a substitute.

A spokesperson for JPL told us: ""With the cover open, we're at a little more risk of dust getting on our optics, but over the past hundred days or so, we haven't seen significant impact or change. It helps that when not in use, the instrument is cradled within Perseverance's folded robotic arm. We're continuing to monitor the impact from dust, but SHERLOC is still collecting great science data so far."

Kyle Uckert, SHERLOC deputy principal investigator at NASA's Jet Propulsion Laboratory (JPL) in Southern California, said: "The rover's robotic arm is amazing. It can be commanded in small, quarter-millimeter steps to help us evaluate SHERLOC's new focus position, and it can place SHERLOC with high accuracy on a target.

"After testing first on Earth and then on Mars, we figured out the best distance for the robotic arm to place SHERLOC is about 40 millimeters [1.58 inches]. At that distance, the data we collect should be as good as ever."

"Six months of running diagnostics, testing, imagery and data analysis, troubleshooting, and retesting couldn't come with a better conclusion," said SHERLOC principal investigator Kevin Hand of JPL.

Perseverance arrived on Mars in 2021 for a prime mission duration of one Martian year (approximately 687 Earth days). It has comfortably exceeded those expectations and is currently in its fourth science campaign.

While engineers are to be applauded for coming up with a solution for the issue, the incident highlights that despite the creativity of the JPL team, every rover will eventually wear out in the harsh environment of Mars. ®

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