123 a similar FMPB feature  to maintain hardware cleanliness requirements for hermetic seals and the volume  probe prior to and between usage on Mars . In the dispensers and volume station, the sample tube  may  only contact surfaces considered clean similar to within a sheath. Refer to Figures 19 , 20, and 21  for  depictions of a glove and cover s in their respective installed cases.  

In addition to precision cleaning and FMPB hardware features  to achieve and maintain  SIH hardware   cleanliness , a high temperature bake- out at 350°C in air for a minimum of 1 hour was prescribed. This bakeout initiate s combustion cleaning for the elimination of viable organisms  and the reduction of organic carbon  on hardware surfaces  and occur s as the last process prior to hardware delivery to the Kennedy Space  Center for installation into the Rover . As a result , the SIH and associated SHH items must participate in the  bake- out together as an assembly, which includes the STSA and the DVT assembl ies. Material selection  was critical for  all STSA and DVT hardware to ensure compatibility  with the high temperature bake- out.  Spring materials such as E lgiloy were implemented versus typical stainless steel options . High temperature  compatible materials were implemented such as Ti -6Al-4V and A286, as well as d ry film lubrications such  as molybdenum disulfide (MoS 2) and tungsten disulfide (WS 2). Non- metallics were not permitted d ue to the  temperature requirement.  

All other ACA hardware was exposed to both a station- level and a full ACA -level bake- out at 110°C for  durations up to 141 hours . These bake- outs were a Dry -Heat Microbial Reduction for PP purposes, as well  as to meet surface cleanliness and outgassing requirements for CC . Thermoelectrically Controlled Quartz  Crystal Microbalance was implemented to verify outgassing rates were met during bake- outs in thermal  vacuum environments . 

Overall, t he PP and CC constraints introduced a number of challenges that resulted in novel hardware  solutions, as well as hardware processing changes along the way due to lessons learned discussed later  in this paper . 

ACA Station Descriptions  

Bit Carousel   The Bit Carousel (BC)  is mounted to the CCMD on the ACA and extends through a cut -out in the Rover top  deck and front panel  to accommodate both tube and bit exchange operations . A non-permeable fabric   close -out covers  the gap between the BC and Rover structures  to prevent contamination from entering the  ACA volume within the Rover  from above.  

The docking assembly is the critical interface between the ACA and  Turret for bit exchange operations with  the Corer  and is mounted to the front of th e BC (Figure 7). During bit exchange, four docking posts on the  Corer structure engage the docking cones on the docking assembly as the RA brings the Turret closer to  the BC. Due to the kinematic s of the 5- DOF RA, continued advancement of the Corer  results in a rotation  of the Corer on the end of the RA, meaning the docking posts are now rotating with respect to the docking  assembly . The docking assembly therefore rides on a passive bearing mechanism that compensates  for  this Corer rotation. The bearing mechanism consists of a dry film lubricated four -point contact (X -type)  bearing from Kaydon , implemented due to packaging limitations . Docking is considered complete once  contact switch mechanisms located at the bottom of each docking cone are fully activated  and the desired  preload force is achieved . A minimum of 3 out of 4 switch activations are required to proceed. Because of  the induced rotation during docking, a single speed variable reluctance resolver from Ducommun, Inc. is  implemented on the docking assembly to measure the resulting amount of rotation, which is  used to adjust  for Corer -to-bit orientation during bit exchange. When the Turret undocks from the BC , a return spring  mechanism brings the docking assembly back to its original position to support the next docking operation.  The return spring mechanism consists of a cam roller  design, with a detent in the cam to center the  mechanism,  and the roller located at the end of a flexure to enforce re- centering.