As seen in this artist’s concept, the SHERLOC instrument is located on the end of the robotic arm of NASA’s Perseverance Mars rover. Credit: NASA/JPL-Caltech
After six months of effort, an instrument that helps 
Imagery captured by a navigation camera aboard NASA’s Perseverance rover on Jan. 23 shows the position of a cover on the SHERLOC instrument. The cover had become stuck several weeks earlier but the rover team has since found a way to address the issue so the instrument can continue to operate. Credit: NASA/JPL-Caltech
Mounted on the rover’s robotic arm, SHERLOC uses two cameras and a laser spectrometer to search for organic compounds and minerals in rocks that have been altered in watery environments and may reveal signs of past microbial life. On January 6, a movable lens cover designed to protect the instrument’s spectrometer and one of its cameras from dust became frozen in a position that prevented SHERLOC from collecting data.
Analysis by the SHERLOC team pointed to the malfunction of a small motor responsible for moving the protective lens cover as well as adjusting focus for the spectrometer and the Autofocus and Context Imager (ACI) camera. By testing potential solutions on a duplicate SHERLOC instrument at JPL, the team began a long, meticulous evaluation process to see if, and how, the lens cover could be moved into the open position.
The cover for the Autofocus and Context Imager on SHERLOC — one of the instruments aboard NASA’s Perseverance Mars rover — is seen moving in images captured by the rover’s Mastcam-Z instrument on May 11. Credit: NASA/JPL-Caltech/ASU/MSSS
SHERLOC Sleuthing
Among many other steps taken, the team tried heating the lens cover’s small motor, commanding the rover’s robotic arm to rotate the SHERLOC instrument under different orientations with supporting Mastcam-Z imagery, rocking the mechanism back and forth to loosen any debris potentially jamming the lens cover, and even engaging the rover’s percussive drill to try jostling it loose. On March 3, imagery returned from Perseverance showed that the ACI cover had opened more than 180 degrees, clearing the imager’s field of view and enabling the ACI to be placed near its target.
Perseverance’s team used the SHERLOC instrument’s Autofocus and Context Imager to capture this image of its calibration target on May 11 to confirm an issue with a stuck lens cover had been resolved. A silhouette of the fictional detective Sherlock Holmes is at the center of the target. Credit: NASA/JPL-Caltech
“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.”
Like any good ophthalmologist, the team set about figuring out SHERLOC’s prescription. Since they couldn’t adjust the focus of the instrument’s optics, they relied on the rover’s robotic arm to make minute adjustments in the distance between SHERLOC and its target in order to get the best image resolution. SHERLOC was commanded to take pictures of its calibration target so that the team could check the effectiveness of this approach.
The calibration target for SHERLOC, one of the instruments aboard NASA’s Perseverance Mars rover, features a slice of Martian meteorite, plus spacesuit materials, including helmet-visor material that doubles as a geocache target. Credit: NASA/JPL-Caltech
“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 
This image of NASA’s Perseverance rover gathering data on the “Walhalla Glades” abrasion was taken in the “Bright Angel” region of Jezero Crater by one of the rover’s front hazard avoidance cameras on June 14. The WATSON camera on the SHERLOC instrument is closest to the Martian surface. Credit: NASA/JPL-Caltech
“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. It’s hypothesized that this also might be the case for the Margin Unit, which formed over 3 billion years ago.
Mars 2020 Perseverance Mission
The Mars 2020 Perseverance mission, launched by NASA, is part of the agency’s Mars Exploration Program. Its primary goal is to seek signs of ancient life and collect samples of rock and regolith (broken rock and soil) for possible return to Earth.
The Perseverance rover landed on Mars on February 18, 2021, in the Jezero Crater, a site believed to have been the basin of an ancient river delta. The mission is also pioneering the technology needed for future human and robotic exploration of Mars. Key objectives include the study of Martian climate and geology, the search for signs of ancient life, the collection of Mars samples, and the preparation for human exploration. In addition to its scientific instruments, Perseverance carries the Ingenuity helicopter, demonstrating powered flight on another planet for the first time.
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