As shown in this artist’s concept, the SHERLOC instrument is located at 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 NASA‘s Perseverance Mars Rover’s search for possible signs of ancient microbial life is back online.
After a mechanical failure halted SHERLOC operations on the Perseverance rover, NASA engineers performed rigorous testing and innovative solutions to restore the instrument. Their efforts, which included manipulating the rover’s components to free a stuck lens cover, enabled continued exploration and data collection on Mars, focusing on geological signs of ancient life.
For the first time since the problem occurred last January, the SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals) instrument aboard NASA’s Perseverance Mars rover has analyzed a rock target with its spectrometer and camera. The instrument plays a key role in the mission’s search for signs of ancient microbial life on Mars. Engineers at NASA’s Jet Propulsion Laboratory (JPL) in Southern California confirmed June 17 that the instrument had successfully collected data.
“Six months of performing diagnostics, testing, imaging and data analysis, troubleshooting and retesting could not have produced a better conclusion,” said Kevin Hand, SHERLOC principal investigator. JPL.
Images captured on Jan. 23 by a navigation camera aboard NASA’s Perseverance rover show 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 fix the problem so the instrument can continue operating. 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 that could reveal signs of past microbial life. On Jan. 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 indicated a malfunction of a small motor responsible for moving the protective lens cover and adjusting the focus for the spectrometer and the Autofocus and Context Imager (ACI) camera. Testing possible solutions on a duplicate SHERLOC instrument at JPL, the team began a long, painstaking 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 in motion in images captured May 11 by the rover’s Mastcam-Z instrument. Credit: NASA/JPL-Caltech/ASU/MSSS
SHERLOC detective work
Among many other steps the team took, it tried heating the lens hood’s small motor, commanded the rover’s robotic arm to rotate the SHERLOC instrument in different directions with supporting Mastcam-Z images, rocked the mechanism back and forth to dislodge any debris that might be blocking the lens hood, and even engaged the rover’s percussion drill to try to shake it loose. On March 3, images returned to Perseverance showed that the ACI hood had opened more than 180 degrees, clearing the imager’s field of view and allowing the ACI to be positioned close to its target.
The Perseverance team used the SHERLOC instrument’s Autofocus and Context Imager to capture this image of the calibration target on May 11 to confirm that a stuck lens cover issue had been resolved. A silhouette of fictional detective Sherlock Holmes is seen at the center of the target. Credit: NASA/JPL-Caltech
“With the cover out of the way, there was a line of sight for the spectrometer and the camera. 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 out to figure 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 small adjustments to the distance between SHERLOC and its target to get the best image resolution. SHERLOC was instructed to take pictures of its calibration target so the team could verify the effectiveness of this approach.
The calibration target for SHERLOC, one of the instruments aboard NASA’s Perseverance Mars rover, includes a piece 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 controlled in small quarter-millimeter increments to help us evaluate SHERLOC’s new focus position, and it can move SHERLOC at high accuracy on a target,” Uckert said. “After testing first on Earth and then on Mars, we found that 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 ACI’s good positioning on a Martian rock target was provided on May 20. Verification on June 17 that the spectrometer is also functional ticked the team’s final box, confirming that SHERLOC is operational.
This image of NASA’s Perseverance rover collecting data on the “Walhalla Glades” wear surface was taken June 14 in the “Bright Angel” area of Jezero Crater by one of the rover’s forward hazard avoidance cameras. 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. Now that SHERLOC is back online, we’re continuing our exploration and sample collection with a full suite of science instruments.”
Perseverance is in the later stages of its fourth science campaign, searching for evidence of carbonate and olivine deposits in the Margin Unit, an area along the inside rim of Jezero Crater. On Earth, carbonates typically form in the shallows of freshwater or alkaline lakes. It is thought that this could be the case for the Margin Unit, which formed more than 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 search for 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 Jezero Crater, a site thought to be the basin of an ancient river delta. The mission is also pioneering technology needed for future human and robotic exploration of Mars. Key objectives include studying the climate and geology of Mars, searching for signs of ancient life, collecting Martian samples, and preparing for human exploration. In addition to its science instruments, Perseverance carries the Ingenuity helicopter, which will demonstrate powered flight on another planet for the first time.