The SHERLOC Calibration Target on the Mars 2020 Perseverance Rover: Design, Operations, Outreach, and Future Human Exploration Functions

Abstract

The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is a robotic arm-mounted instrument onboard NASA’s Perseverance rover. SHERLOC combines imaging via two cameras with both Raman and fluorescence spectroscopy to investigate geological materials at the rover’s Jezero crater field site. SHERLOC requires in situ calibration to monitor the health and performance of the instrument. These calibration data are critically important to ensure the veracity of data interpretation, especially considering the extreme martian environmental conditions where the instrument operates. The SHERLOC Calibration Target (SCT) is located at the front of the rover and is exposed to the same atmospheric conditions as the instrument. The SCT includes 10 individual targets designed to meet all instrument calibration requirements. An additional calibration target is mounted inside the instrument’s dust cover. The targets include polymers, rock, synthetic material, and optical pattern targets. Their primary function is calibration of parameters within the SHERLOC instrument so that the data can be interpreted correctly. The SCT was also designed to take advantage of opportunities for supplemental science investigations and includes targets intended for public engagement. The exposure of materials to martian atmospheric conditions allows for opportunistic science on extravehicular suit (i.e., “spacesuit”) materials. These samples will be used in an extended study to produce direct measurements of the expected service lifetimes of these materials on the martian surface, thus helping NASA facilitate human exploration of the planet. Other targets include a martian meteorite and the first geocache target to reside on another planet, both of which increase the outreach and potential of the mission to foster interest in, and enthusiasm for, planetary exploration. During the first 200 sols (martian days) of operation on Mars, the SCT has been analyzed three times and has proven to be vital in the calibration of the instrument and in assisting the SHERLOC team with interpretation of in situ data.

SHERLOC Raman Mineral Class Detections of the Mars 2020 Crater Floor Campaign

“…By doing so, we obtained spectra with maximum peak intensities ≥10X the noise RMSD, which have a peak position error of <±∼1 cm −1 . Combined with the ±1.8 cm −1 uncertainty in the wavenumber calibration (Fries et al, 2022), the peak wavenumber error of the most intense peaks in spectra used to assign mineral classes is approximately ±2-3 cm −1 . However, the error for any specific peak in a single spectrum is dependent on the signal-to-noise ratio and can be estimated using the work of Lenz and Ayres (1992), as described in Text S1 of Supporting Information S1.…”

Overview and Results From the Mars 2020 Perseverance Rover's First Science Campaign on the Jezero Crater Floor

“…Although these bands could be consistent with organics such as aromatic heterocycles, this is not confirmed with Raman. A single point in the Montpezat target exhibited a Raman signal that may be consistent with an organic G band that closely aligns with the known G band on the SaU008 meteorite SHERLOC calibration target (Fries et al, 2022;Sharma et al, 2022); the 340 nm fluorescence was co-located with this Raman detection.…”

Science and Science‐Enabling Activities of the SHERLOC and WATSON Imaging Systems in Jezero Crater, Mars

“…WATSON can be positioned to image rover hardware, acquire mosaics showing the rover within the Martian landscape (i.e., selfies; Figure 3c), and even image features in the sky. WATSON can also image a variety of instrument calibration targets and is therefore critical to instrument calibration activities (Fries et al, 2022). By contrast, ACI was designed to provide context views for SHER-LOC's spectroscopic measurements and to focus SHERLOC's 248.6 nm deep-ultraviolet laser (Bhartia et al, 2021).…”

“…WATSON can be positioned to image rover hardware, acquire mosaics showing the rover within the Martian landscape (i.e., selfies; Figure 3c), and even image features in the sky. WATSON can also image a variety of instrument calibration targets and is therefore critical to instrument calibration activities (Fries et al., 2022).…”