HP³ - Experiment on InSight Mission - Operations on Mars

HP3 – the Heat Flow and Physical Properties Package – is an experiment package on-board the NASA Mars Mission InSight (Interior Exploration Using Seismic Investigation, Geodesy, and Heat Transport). The InSight Mission investigates the interior structure of Mars using seismological and geodetical measurements and quantifies the planetary heat budget by measuring the surface planetary heat flow. InSight was launched on the 5th May 2018 and landed successfully on Mars on the 26th November 2018 and is now operating on Mars successfully for more than one Martian year. The main payloads of the InSight lander are a seismometer (SEIS), the HP3 heat flow probe and radiometer (for surface brightness temperature), as well as the radio science Rotation and Interior Structure Experiment (RISE). An ancillary sensor package consisting of atmospheric pressure and temperature sensors (APSS) as well as a magnetometer complement the payload. After landing on Mars the seismometer and HP3 were deployed onto the Martian surface by the robotic arm of the lander. HP3 is the contribution of DLR (Deutsches Zentrum für Luft- und Raumfahrt e.V., Germany) to the InSight mission. It is designed to determine the geothermal heat flux by measuring the thermal conductivity and the rate of temperature increase with depth. HP3 is composed of a set of thermal sensors to determine thermal conductivity and subsurface temperature (TEM), a self-penetrating probe (termed the mole) to emplace sensors in the subsurface, two measurement suites to determine the depth of the thermal sensors (TLM & STATIL), a radiometer to determine the surface temperature forcing (RAD). The instrument is controlled by (backend) electronics (BEE) within the InSight lander’s thermal enclosure. The HP3 deployable elements are housed inside a support structure, and electrical connections to the lander and BEE are provided by the HP3 supply tethers [1]. The InSight mission has now been operating on Mars for more than one martian year. The radiometer has been monitoring the surface brightness temperature for a full martian year and has measured thermal effects during Phobos eclipses. The heat flow aspect of the HP3 investigation has unfortunately been less successful. The mole penetration initially proceeded no deeper than ~37 cm (tip depth below surface). During the past 2 Earth years, extensive recovery activities for the mole were performed on Mars to get the mole penetrated deeper into the surface. These activities were supported by the overall InSight team. The mole is now in its final position intruded into the upper surface layer (mole tilt ~30°) and covered with soil. No further penetration attempts will be performed