The SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) instrument recently analyzed a rock target with its spectrometer and camera for the first time since encountering an issue in January. Engineers at NASA's Jet Propulsion Laboratory (JPL) confirmed on June 17 that SHERLOC successfully collected data.
"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.
SHERLOC, mounted on the rover's robotic arm, uses two cameras and a laser spectrometer to search for organic compounds and minerals in rocks that have been altered by water, potentially revealing signs of past microbial life. On Jan. 6, a movable lens cover protecting the instrument's spectrometer and one of its cameras from dust became frozen, preventing data collection.
Analysis indicated a malfunction in a small motor responsible for moving the protective lens cover and adjusting focus for the spectrometer and the Autofocus and Context Imager (ACI) camera. The team began a meticulous evaluation process on a duplicate SHERLOC instrument at JPL to see if and how the lens cover could be moved to the open position.
Among many other steps, the team tried heating the lens cover's small motor, rotating the SHERLOC instrument with the rover's robotic arm, rocking the mechanism to loosen debris, and even using the rover's percussive drill to jostle it loose. On March 3, imagery from Perseverance showed that the ACI cover had opened more than 180 degrees, clearing the imager's field of view.
"With the cover out of the way, a line of sight for the spectrometer and camera was established. We were halfway there," said Kyle Uckert, SHERLOC deputy principal investigator at JPL. "We still needed a way to focus the instrument on a target. Without focus, SHERLOC images would be blurry and the spectral signal would be weak."
The team then relied on the rover's robotic arm to make precise adjustments in the distance between SHERLOC and its target to achieve the best image resolution. SHERLOC was commanded to take pictures of its calibration target to check this approach.
"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," said Uckert. "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," or 1.58 inches. "At that distance, the data we collect should be as good as ever."
Confirmation of the proper positioning of the ACI on a Martian rock target came on May 20. The final verification that the spectrometer is functional came on June 17, confirming SHERLOC is fully operational.
"Mars is hard, and bringing instruments back from the brink is even harder," said Perseverance project manager Art Thompson of JPL. "But the team never gave up. With SHERLOC back online, we're continuing our explorations and sample collection with a full complement of science instruments."
Perseverance is in the later stages of its fourth science campaign, looking for evidence of carbonate and olivine deposits in the "Margin Unit," an area along the inside of Jezero Crater's rim. On Earth, carbonates typically form in the shallows of freshwater or alkaline lakes, which might also be the case for the Margin Unit, formed over 3 billion years ago.
Related Links
SHERLOC Instrument on Perseverance Rover
Mars News and Information at MarsDaily.com
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