Application  BB orsuper-  Duplex GOMOS SFA  Giotto De-Spin  cantilevered -but  with 3d hold-down  loads - 1.5-3 kN > 5.4~1 O5 Nm/rad I  -50-85 points (Launch 1200 N (min) for  launch stiffness mm Optical Terminal  BB or FF &  Spring/Diaphragm APM with RF  Feedthrough (Bepi-  Colombo)  I  2o ym Up to 1-2 kg >loo-150 HZ (typ. SADM (BAPTA)  1 >loo I >60 kg mm BB ReactionlMomentum  WheeVCMG  >70 Hz Swash Plate APM  Push-Broom Scanner  (EGPM) Table 1. Summary HistoridRecent Application Details  Face-Face:FF  FFIBB >160 Hz / Minimize I (e.g., 30-300 N) I KA075 I 2kg1120mm  plus  102 Nm)  BB&Diaphragm 1 25mm I Unknown >lo0 Hz / 45 N in  flight  I 177 mm 1 Unknown 4 Pt Contact  BB Hard Preload I >IO0 Hz/ 1500 N Special  Constraints  BOLD used  BOLD used  Large bore, severe  masslpower  constraints  Bore to  accommodate RF  joint  High launch loads  and moments  BOLD used,  released on-orbit  stiffness must  support solar array  Life target 5x1 0’”  revs  Stiffness on-orbit  adequate for  payload  6x1 O3 Nm/rad. On  orbit  Despin Mechanism (ea. GIOTTO De-spin)  In common with many deep space missions, GIOTTO the last European deep space mission using a spin  stabilized spacecraft, required a de-spun antenna to maintain a high-data-rate communications link to  Earth. The key issues for this type of mechanism are to support the antenna during launch yet provide  long life, low friction and reliable operation in adverse thermal conditions (e.g., with wide fluctuations in  temperatures and temperature gradients).  To maximize bearinghbricant life while maintaining insensitivity to adverse thermal gradients a low  preload was required and applied by means of compliant diaphragm. But launch loads and frequency  constraints for the application could only be met by employing a separate bearing off-load device (BOLD).  Had BAPS technology been available this application could have avoided the need for the BOLD even if a  bearing pair with virtually the same diameter were selected.  Optical Communications  Laser Communications Terminals for inter-satellite communications links are a major application for  pointing mechanisms. One device currently under development is a Course Pointing Assembly. This  device is required to gimbal a high precision mirror through large angles. The bearing must be almost free  of stick-slip effects and must provide a through-bore sufficiently large to allow the passage of an optical  beam (typically 15-mm dia.) through the azimuth gimbal. To achieve both of these requirements in a  mass- and cost-effective manner ideally requires high bearing preloads during launch and very low  preloads once on-orbit.  A preliminary assessment suggests that launch requirements could be fully met at low risk if launch  preload could be set at 2000 N, provided preload is released to less than 200 N once on orbit. The use of  BAPS could provide an even larger range than this and would provide a lower risk solution than the use of  a fundamentally lower fixed preload and snubbers to limit rotor motion during launch vibration. The latter  conventional approach allows hammer like contact at the bearing and drive gear contacts which increase  risk of degraded life-time and in-orbit performance.  138