Curiosity’s Mars Hand Lens Imager (MAHLI) Investigation

Abstract

The Mars Science Laboratory (MSL) Mars Hand Lens Imager (MAHLI) investigation will use a 2-megapixel color camera with a focusable macro lens aboard the rover, Curiosity, to investigate the stratigraphy and grain-scale texture, structure, mineralogy, and morphology of geologic materials in northwestern Gale crater. Of particular interest is the stratigraphic record of a ∼5 km thick layered rock sequence exposed on the slopes of Aeolis Mons (also known as Mount Sharp). The instrument consists of three parts, a camera head mounted on the turret at the end of a robotic arm, an electronics and data storage assembly located inside the rover body, and a calibration target mounted on the robotic arm shoulder azimuth actuator housing. MAHLI can acquire in-focus images at working distances from ∼2.1 cm to infinity. At the minimum working distance, image pixel scale is ∼14 µm per pixel and very coarse silt grains can be resolved. At the working distance of the Mars Exploration Rover Microscopic Imager cameras aboard Spirit and Opportunity, MAHLI's resolution is comparable at ∼30 µm per pixel. Onboard capabilities include autofocus, autoexposure, sub-framing, video imaging, Bayer pattern color interpolation, lossy and lossless compression, focus merging of up to 8 focus stack images, white light and longwave ultraviolet (365 nm) illumination of nearby subjects, and 8 gigabytes of non-volatile memory data storage.

MAHLI on Mars: lessons learned operating a geoscience camera on a landed payload robotic arm

“…MAHLI is a 2-megapixel, color camera with a macro lens that is able to focus on targets at working distances from 2.1 cm to infinity (Edgett et al, 2012; working distance is measured from the camera lens to the target). The camera head is mounted on a rotatable turret at the end of Curiosity's robotic arm ( Fig.…”

“…8; Robinson et al, 2013); 8. observations of landscape geomorphology ( Fig. 9) and airborne dust; 9. imaging of other instrument hardware (e.g., the APXS calibration target, the CheMin inlet funnel, the Sample Analysis at Mars (SAM) tunable laser spectrometer (TLS), the Rover Environmental Monitoring System (REMS) ultraviolet (UV) sensor and the ChemCam remote warm electronics box (RWEB)) to support their safety and health (Blake et al, 2013;Edgett et al, 2012;Gómez-Elvira et al, 2012;Wiens et al, 2012;Campbell et al, 2014;Figs. 10-12); and 10. observations of the properties and configuration of eolian dust that settled on natural and rover hardware surfaces (Fig.…”

“…13). A tool specifically designed to remove dust and provide contact instrument access to fresh rock surfaces, such as the descoped surface removal tool (SRT; Edgett et al, 2012) or a notional robotic rock hammer, would have been more beneficial. In lieu of such a tool, targets that have been disturbed by the rover or other hardware (e.g., broken rocks, disturbed regolith) can also provide cleaner or fresh surfaces, but opportunities to view these have been limited.…”

“…When using an artificial light source, phase angle can reduce apparent depth, which in turn lessens textural heterogeneity and challenges autofocus; MAHLI's white light LEDs, which are at different positions and can operate independently (Edgett et al, 2012), can provide shadowing, lessening this problem. When imaging at night, the placement of the LEDs is adjusted to create the best image.…”

“…The goal of the MAHLI science investigation is to identify and interpret lithologic and textural clues that reveal processes responsible for forming and modifying the geologic record at the rover's field site in Gale crater (Edgett et al, 2012). We present here a brief overview of the MAHLI investigation activities and results from the first 1150 sols, and the key lessons learned in operating this instrument.…”