328 For the sake of brevity, only the plots from a selection of these tests are shown in accordance with their  potential to cause the anomalous behavior.   Conclusion s  The anomaly in the SCS bearing assembly has been humbling, but interesting. A Brassboard assembly  was built and tested to provide validation of the design concept and tools. Deviations to the design were  made between the Brassboard and EM/FM designs  that were expected to reduce stresses in the bearing  assembly. Test results have shown that there was  design oversight in the process used for the SCS bearing  assembly. The root cause investigation eliminated several  potential contributors or reasons for the anomaly.  However, the team is still left with questions.   • Did the anomaly occur during vibration testing, but only appear  during TVAC due to some shift in  the position of the ball track?  • Is the anomaly a function of temperature or temperature gradients only? If so, why isn’t drag in the  system unexpectedly high for the full stroke of the mechanism? Average drag actually remained  reasonably consistent with predictions.   • Is friction between the bearing and the shaft and housing too large to ensure the intended clamping  over the temperature range, given the CTE mismatch?   • Was the problem with the clamp stiffnes s? If so, this would indicate that the anomaly occurred  during vibration testing as non- rigid clamps would only r educe stresses during thermal cycling.   There are currently no plans in place to perform more tests, inspections, disassembly, or otherwise to find  the true root of the problem for this assembly. However, there are some good lessons learned, or good  reminders of lessons that have been learned previously by others. These are true particularly for thin section  bearings which can be more sensitive to design parameters.   • Fundamentally  sound designs should be the starting point. In this case, use matching CTE  materials , “rigid” clamps , and avoid mixed material designs  that are difficult to model  (e.g. the gear  in the SCS assembly was restricting the growth of the housing).   • Question requirements if they are dictating solutions  that are difficult to analyze and push back if  necessary .  If the opportunity exists to pursue this investigation further there are more tasks that  could  be performed to  help identify the root cause. These include disassembly of the EM to inspect the raceways; and assembly  and test (both vi bration and TVAC) of a few more units with changes to specific variables such as clamp  stiffness, housing and shaft friction, and CTE mismatch.   Acknowledgments   This research was carried out at the Jet Propulsion Laboratory, California Institute of Technolo gy, under a  contract with the National Aeronautics and Space Administration (80NM0018D000 4), subcontract 1531184.   References   1. ESA 2000 -2019, “Sentinel -6 Mission.” https://sentinel.esa.int/web/sentinel/missions/sentinel -6. Accessed  December 23, 2019.   2. ESA 200 0-2019, “Sentinel -6 / Jason-CS.” https://directory.eoportal.org/web/eoportal/satellite- missions/content/ - /article/jason-cs. Accessed December 23, 2019.   3. Halpin, Jacob, D., “Ball Bearing Analysis with the ORBIS Tool,” Proceedings of the 43rd Aerospace Mechanisms  Symposium, NASA Ames Research Center, May 4 -6, 2016.   4. NASA Technical Standard. “Design and Development Requirements for Mechanisms.” NASA -STD -5017A  w/CHANGE 1. 2016 -05-31.  5. Singer, H., “Space Vehicle Mechanisms: Elements of Successful Design,” ed. Conley, P., John Wiley & Sons, 1998.  Ch. 12, p. 305.   6. Videira, et al. “Design, Assembly and Preloading of Ball Bearings for Space Applications – Lessons Learned and  Guidelines for Future Success.” Proceedings of ESMATS. Noordwijk, The Netherlands . 25-27 September 2013.