51 Development and Testing of a “Backlash -Free”  Gas-Tight High- Precision Sample  Dosing M echanism for the ExoMars 2018 Rover  

Daniel Redlich*, Robert Paul *, Sebastian Ott *, Lutz Richter*,  Quirin Mühlbauer *, Markus Thiel *,   Tim Tattusch* , Harald Weisz**, Fabio Musso*** and Stephen Durrant****  

Abstract  

This paper presents the development and testing by OHB System AG of the Powdered Sample Dosing and Distribution System (PSDDS) with specific focus on the bearing and sealing design. The PSDDS is a sample handli ng mechanism on the R over of the European Space Agency 2018 ExoMars Mission, a  cooperative mission with Roscosmos including a scientific instrument contribution from NASA. It is entirely developed by OHB as a subcontractor to Thales Alenia Space Ital ia who is the prime contractor  for the whole ExoMars program . The PSDDS is the third part of a chain consisting of four individual  mechanisms that compose the Sample Preparation and Distribution System (SPDS).    The main task of the PSDDS  is to receive powdered samples from a stone mill (Crushing Station)  and  distribute the samples in defined quantities to two different kinds of receptacles, a refillable cont ainer and  several one- time use O vens , which are mounted on a carousel (4th mechanism).  The sample dis tribution  is performed by a redundant Dosing Station (DS). As these powdered samples are quite sensitive to  cementation, two counter -measures have been implemented. A Piezo to vibrate the Dosing Station and to  loosen the sample material as well as a device  to bypass the two D osing S tations which is able to  distribute the sample in a more robust way but without the capability to control the amount (A lternative  Transport Container ( ATC)). Another task of the PSDDS  is to clean the refillable container to allow  its  reuse without cross contaminating the samples (Cleaning Device).    These components and procedures need to be compatible with the Martian environment.  This includes   sample handling and challenging demands for cleanliness and contamination control resul ting in stronger  constraints for  the mechanism ’s design and ultimately requiring the development of unique design  solutions.    The PSDDS design  as well as the results of the qualification  test campaign under Mars -like conditions are  described  in this paper . 

Introduction  

Exploring whether life ever existed or is still present on Mars today  is one of the most exciting scientific  questions of our time. Therefore, ESA together with Roscosmos  decided to conduct the ExoMars  program , which is divided into two mis sions:  the first mission consists of an Orbiter plus an Entry, Descent  and Landing Demonstrator Module to be launched in 2016 whereas the second mission consists of a  Lander with a Rover to be launched in 2018. The Rover is equipped with a Drill to take sub-soil sampl es  down to a depth of 2 m , which will then be analyzed  in-situ by several instruments dedicated to  exobiology and geochemistry research, the so -called Pasteur payload. These instruments  are located in  the Analytical Laboratory Drawer (ALD) inside of the R over. These instruments are:                                                     * OHB System AG, Oberfpfaffenhofen, Germany   ** Weisz, Munich, Germany   *** Thales Alenia Space Italia S.p.A., Torino, Italy   **** ESA-ESTEC , Noordwijk, The Netherlands  

Proceedings of the 43rd Aerospace Mechanisms Symposium, NASA Ames Research Center, May 4-6, 2016