Detective work allows Perseverance Mars rover team to relaunch SHERLOC instrument

After six months of effort, an instrument that helps the Mars rover search for potential signs of ancient microbial life is back online.

The SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals) instrument aboard NASA’s Perseverance Mars rover has scanned a rocky target with its spectrometer and camera for the first time since it encountered a problem last January. The instrument plays a key role in searching for signs of ancient microbial life on Mars. Engineers at NASA’s Jet Propulsion Laboratory in Southern California confirmed June 17 that the instrument had successfully collected data.

“Six months of diagnostics, testing, imaging and data analysis, troubleshooting and retesting could not have resulted in a better conclusion,” said Kevin Hand, SHERLOC principal investigator at JPL.

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 weathered in aqueous environments and which 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 froze in a position that prevented SHERLOC from collecting data.

The SHERLOC team’s analysis revealed a malfunction in a small motor that moves the objective lens cover and adjusts the focus of the spectrometer and the Autofocus and Context Imager (ACI) camera. Testing potential solutions on a duplicate SHERLOC instrument at JPL, the team began a lengthy and meticulous evaluation process to see if and how the objective lens cover could be moved into the open position.

Investigation into SHERLOC

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 in different orientations with Mastcam-Z imaging, rocking the mechanism back and forth to loosen debris that might be blocking the lens cover, and even engaging the rover’s impact drill to try to loosen it. On March 3, images sent back from Perseverance showed that the ACI cover had opened more than 180 degrees, clearing the imager’s field of view and allowing the ACI to be positioned close to its target.

“Once the cover was removed, 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 focusing, SHERLOC images would be blurry and the spectral signal would be weak.”

Like any good ophthalmologist, the team set about determining the prescription for SHERLOC. Since they couldn’t adjust the focus of the instrument’s optics, they relied on the rover’s robotic arm to make fine adjustments to the distance between SHERLOC and its target to achieve the best resolution. ‘picture. SHERLOC was ordered to take photos of its calibration target so the team could verify the effectiveness of this approach.

“The rover’s robotic arm is incredible. It can be controlled in small quarter-millimeter steps to help us evaluate SHERLOC’s new focus position, and it can place SHERLOC very accurately on a target,” Uckert said. “After testing on Earth and then on Mars, we’ve determined that the best distance the robotic arm can 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 this successful positioning of the ACI on a Martian rock target came on May 20. Verification on June 17 that the spectrometer was also functional checked the team’s final box, confirming that SHERLOC is operational.

“The Mars mission is tough, and bringing instruments back from the surface is even tougher,” said Art Thompson, Perseverance project manager at JPL. “But the team never gave up. With SHERLOC back up and running, we’re continuing our exploration and sample collection with a full suite of science instruments.”

Perseverance is in the final stages of its fourth scientific campaign, searching for evidence of carbonate and olivine deposits in the “Margin Unit”, an area located inside the rim of Jezero Crater. On Earth, carbonates typically form in the shallows of freshwater or alkaline lakes. It is speculated that this could also be the case for the margin unit, formed more than 3 billion years ago.