HP3 Instrument Support System Structure development for the NASA/JPL Mars Mission InSight

Abstract

On May 05, 2018 NASA JPL launched its mission to Mars called “InSight”. Main objective of this mission is to gain more knowledge about the evolution of terrestrial planets and to more precisely determine properties of core, mantle and crust of Mars. One of a number of different scientific instruments onboard the lander there will be HP3 (Heat Flow and Physical Properties Package), which was developed by the German Aerospace Center (DLR). It will be operated on Martian ground to measure the heat flow through the Martian outer crust. It uses a hammering mechanism which will pull a tether approx. 5 m into the soil. The hammering device is equipped with foil heaters on the outer hull and the tether is equipped with temperature elements. Both is needed for the determination of the thermal conductivity of the surrounding regolith and the measurement of the temperature gradients in the ground. There is the need of a separate system to be able to perform those activities on the surface. This system is called the “HP3 Support System”. Its main task is to ensure a stable, nearly perpendicular position of the hammering mechanism relative to the soil on the Martian surface before initial penetration. It furthermore houses the instruments for length measurement and serves as electrical connection to the lander. The paper will give an overview of the development and the qualification of the structure of the Support System. It will focus on the mechanical design, the analysis of the structural dynamics but in particular on the testing which includes standard environmental testing but also numerous development tests that are very mission specific. The mechanical design of the Support System is mainly driven by a unique set of requirements derived from the working environment on Mars, the deployment from the lander deck and the mechanically separated operation on the surface. The instrument design will be explained to show, which design elements were implemented to ensure proper functionality. Various development tests had to be performed during the Support System structure development. Besides the standard qualification tests, special tests were developed to show compliance of the instrument design to the requirements. Such tests are: Separation Tests from the lander deck in cold environment under various tilt angles, Tether Deployment Tests, under various temperatures, foldings and routings, Feet Sliding Resistance Tests on sand with different slopes. The paper will give an overview on all tests necessary for the support system qualification and will describe test setups and the results.