260 Lessons Learned   For each qualification t est the major lessons learned are:  

The Bearing Characterization Breadboard Test  provided at an early project state a series of very  important results (lubrication verification, correct torque budget inputs, possible bearing working profile) .  As a lesson learned,  this test will be standardized within the mechanism department to be used for all  upcoming projects, in order to improve the internal bearing lubrication and torque database.  

The adequate  Life Test  conditioning proved to be challenging when using a simplified Life Test Model.  Therefore for further projects , if possible,  the EM will be used instead of a simplified model. A lot of effort  in the extra assessment and testing can be saved.    The Performance Test  showed that the chosen technical solution (stepper motor, backlash- free gear  with a low medium gear ratio and a bear ing in O -configuration) can pro vide the needed accuracy of  0.1 deg without any challenges.  

The RF Test  demonstrated the possibility  to reduce cost  and time to integration by selecting a novel  supplier. The RF performance was outstanding.  This shall suppor t an open supplier selection for the  future.  

The Vibration Test qualified the X and Z axes for a load input of 20G . Y-axis was qualified up to for 5G   load input , as the load dependent effects had to be investigated in detail . The vibration test also showed  the high value of such EM testing in order to reveal design challenges , occurring due to changes from  heritage design solution.  Functional analysis within the mechanism development process, connecting  function to design elem ents could also help for future projects . With the proposed and investigated minor  structural improvements the APM has proven its viability for the usage in the constellation program.  

The lessons learned of the TVAC Test  will be presented at the  AMS conf erence.    The Microvibration Test and the Magnetic Moment Test  are demonstrating a conflict of requirements.  On the one hand side a certain velocity and accuracy is demanded. On the other side the motor sizing  leads to the violation of the microvibration and magnetic moment requirement s. This conflict of goals has  to be assessed  with the contractor . If the violation of the two named requirements cannot be accepted a  more complex motorization concept has to be chosen (e. g., closed- loop B rushless DC Motor ). 

Acknowledgment 

The author thanks the co- authors and the whole Intersatellite Link Study team for the support and the  shared effort.  Special t hanks to ES A for the funding of the Inters atellite Link Study.  

References  

1.  Danilidis, C., Eben, K., Lindemann, U.  "A functional analysis approach for product reengineering” ,  Procedia Engineering 9  (2011), 270-280.  2.  M. Vitelli, B. Specht, F. Boquet, A process to verify the microvibration and pointing stability requirements for the Bepi Colombo mission,  ESA International Workshop on Instrumentation for  Planetary Mission.  (2012)   3. Kozilek, H., Specht, B., Soon Yong, S., Gyu Lee, S. “Micro Vibration Improvement of a stepper actuated mechanism“ , ESMATS 2013 , September 2013