up the slip rings as long as the slip rings are not noisy to the point that the motor cannot be commutated  (the resolver is also used to commutate the motor). The ability to run many of these troubleshooting  modes has proven invaluable in troubleshooting and recovering from problems both on the ground and  on-orbit.  Conclusion  The Windsat BAPTA is a long-life precision spin drive assembly with challenging requirements and a  difficult development program. As of November 2005, it has operated for 2.5 years of its 3 year life goal  and it continues to operate well enabling Windsat to generate good wind speed and direction data.  However, after two years of operation, evidence of slip ring noise on the resolver rings has appeared  which has resulted in speed anomalies requiring safe-hold recovery operations. Looking back on the  experiences gained during the development and on-orbit operations some key things were done well and  should be done again (good heritage) and some things could be improved next time (bad heritage). A  brief recap of the key items follows:  What Worked Especiallv Well  Redundancv and Robust Desian Marains  Without robust margins the BAPTA development schedule would have been “broken” and without  redundancy (in ways unanticipated) the BAPTA would not still be operating. Windsat was a low-cost,  low reliability experimental mission and a programmatic decision was made to forgo any redundancy  to contain cost. However, a cost-benefit analysis was presented to management which convinced  management to allow redundancy on the BAPTA (the only redundancy flown on Windsat).  Partner Relationshir, Between Government and Slip Rina Vendor  NRL and the slip ring vendor combined strengths and areas of expertise to build a better product.  NRL provided assistance with bearing design and analysis as well as thermal analysis allowing the  slip ring vendor to concentrate on the rest of the slip ring design.  Desian For Test & Troubleshooting  Designing for test and troubleshooting up front allowed many problems to be solved both on the  ground and on-orbit. Some key items were: the ability to spin in both directions, run open loop, and  turn on both sides of the electronics simultaneously.  What Could Be Done BettedDifferent Next Time  Don’t pass critical BAPTA feedback (resolver) over lona-life slir, rinas  An optical encoder was dropped early on for budgetary reasons and with hindsight one should trade  alternate position feedback devices that do not require slip rings. Alternately, better methods of  preventing slip ring noise from affecting resolver signals could be pursued.  Noise sensitive lona-life slip rinas for space remain challenainq  Based on Windsat experience and recent development and testing on other programs a trade study  should be revisited on gold vs. silver/MoS2 vs. non-contacting (i. e., fiber optic, capacitive coupled)  “slip rings” for long-life noise sensitive applications.  Desian slip rina brushes to accommodate thermal expansion  Windsat copied DSCSll heritage brush design and the power brush design was good with a low  “spring constant” that was insensitive to wear and thermal expansion but the critical signal brushes  had a high ”spring constant”and should have been designed the same as the power brushes.  References  Phinney, Damon, “Slip Ring Experience in Long Duration Space Applications.” 2dh Aerospace  Mechanisms Symposium, (1 986),pp 45-54.  222