Results from InSight Robotic Arm Activities

The InSight lander carries an Instrument Deployment System (IDS) that includes an Instrument Deployment Arm (IDA), scoop, five finger “claw” grapple, forearm-mounted Instrument Deployment Camera (IDC) requiring arm motion to image a target, and lander-mounted Instrument Context Camera (ICC), designed to image the workspace, and to place the instruments onto the surface. As originally proposed, the IDS included a previously built arm and flight spare black and white cameras and had no science objectives or requirements, or expectation to be used after instrument deployment (90 sols). During project development the detectors were upgraded to color, and it was recognized that the arm could be used to carry out a wide variety of activities that would enable both geology and physical properties investigations. During surface operations for two martian years, the IDA was used during major campaigns to image the surface around the lander, to assist the mole in penetrating beneath the surface, to bury a portion of the seismometer tether, to clean dust from the solar arrays to increase power, and to conduct a surface geology investigation including soil mechanics and physical properties experiments. No other surface mission has engaged in such a sustained and varied campaign of arm activities directed at such a diverse suite of objectives. The IDA and IDC carried out a wide variety of imaging campaigns including: stereo panoramas at three different times of day, imaging of the workspace at two different resolutions for selecting the sites to place the instruments, stereo imaging beneath the lander to document the alteration of the surface by the retrorockets, regular imaging of the sky to get optical depth for power management and solar array performance, dust devil searches, cloud imaging, sky surveys, closely spaced stereo images to create high-resolution topographic maps, and astronomical imaging. These images fueled a robust geology investigation that provided key information about surface geology, important processes that shaped the surface, and the subsurface stratigraphy important for interpreting the seismic investigations. Images close to the surface and continuous meteorology measurements provided important constraints on the threshold friction wind speed needed to initiate aeolian saltation and surface creep. IDC images of the workspace allowed the selection of locations to place the instruments and their deployment onto the surface within the first 90 sols. The IDA was used extensively for almost 22 months to assist the mole in penetrating into the subsurface by removing the support structure, imaging the mole to understand its state, pushing the mole with the scoop to assist penetration, and scraping soil and tamping it down to fully bury the mole to allow thermal conductivity measurements and a better understanding of the shallow physical properties. Soil was scraped into piles, scooped by the arm and dumped onto the seismometer tether six times in an attempt to bury the tether to reduce noise. Soil, composed dominantly of sand size particles, was dumped by the scoop from ~50 cm above the surface and was entrained in the wind and dispersed downwind 1-2 m, darkening the surface. Because power generated by the solar panels had been reduced by 90% in almost two martian years, seven solar array cleaning experiments were conducted by dumping scoops of soil from 35 cm above the lander deck during periods of high wind that dispersed the sand onto the panels with sufficient kinetic energy to kick dust off of the panels into suspension in the atmosphere, thereby increasing the power by 10%. Final IDA activities included atmosphere and surface imaging, an indentation experiment that used the IDA scoop to push on the ground to measure the plastic deformation of the soil that complemented soil mechanics measurements from scoop interactions with the surface, and two experiments in which SEIS measured the tilt from the arm pressing on the ground to derive near surface elastic properties. Estimation of the forces imparted by the IDA scoop during these activities took place in the JPL testbed.