333 Table 2.  Mechanism Usage Summary Over 16 Y ears in Orbit (to 1 7 Jan 2016 )  Mechanism  Gas Fill  Freq/ Rate  Key Unit Parameters  Years  Nominal  Running  Cycles/  Rotations / Steps * Mechanism Status  Specific Notes   Cooler 1 (B) – Compressor  He 44/43  Hz 13 bar fill pressure  (abs)  15.5 2.1E+10   cycles  Continues to operate  nominally . ~3 months  for investigations.   Displacer ceased nominal operation in  07 May 2001  Current compressor  Stroke (A,B)=(6.24,5.00  mm p-p). Displacer s trokes  (A,B)= (2.99,3.69 mm p-p)  Displacer B continues to  move freely, driven by  pressure wave as per  Figure 9. Cooler 1 (B) -   Displacer  He 44/43  Hz 90 K cold -tip  (transitioning to   ~310  K, 326  K) 1.2 1.6E+09   cycles   Cooler 2 (A)  Compressor &  Displacer  He 44/43  Hz 84 K±0.3  K over life  15.5 2.1E+10   cycles  Continues to operate  nominally  14 decontamination  cycles completed   PMC 1  CO  7.5kPa  48.6 Hz Q factor of ~3, drive  current of X  15.7 2.4E+10   cycles  Continues to operate  nominally  Characterisations  performed during  decontamination cycles,  used to monitor  resonance/fill pressure.  PMC  2 losing ~1% of  pressure per year,  current temp of 297-300 K. PMC amplitudes  (1,2)=(4.84, 6.41mm)  PMC 2  CO  3.8kPa  43.3 Hz Q factor of ~ 7 (at lower  pressure) , Drive  current of 0.2A  15.7 2.1E+10   cycles  Continues to operate  nominally   Chopper 1   25.1 Hz Nye 2001T (130mg),  TCP soaked 440C R6 dupl ex bearings  preload of 12.6±4.4N, Meldin 9000 retainers .  Lubricant Screening by Draper Labs  (up to 5  cycles).   Optical encoder 16  pulses/rotation.  15.7 1.2E+10   rotations  Continues to operate nominally  All choppers have 16  vane openings . Duplex  bearings operate in  vacuum.   1505  rpm  Chopper 2  30.4 Hz 15.7 1.5E+10   rotations  Continues to operate nominally    1822  rpm  Chopper 3   25.1 Hz 1.3 1.0E+09   rotations  Stopped in open vane  position  04-Aug-2001 Chopper 3 failure had no impact to science, due to  stability of  signal/background    1505  rpm  Chopper 4   27.1 Hz  15.7 1.3E+10   rotations  Continues to operate  nominally    1624  rpm  LMC 1  CO  20kPa  11.2 Hz Nye 2001T (130mg), TCP soaked 440C R6  duplex bearings  preload of 22±4.4N,  Meldin 9000 retainers .   Lubricant screening by Draper Labs . Optical  encoder with 72 pulses/rotation.     15.7 5.5E+09   rotations  Continues to operate  nominally  Modulator duplex bearing  run in gas . Compensator  duplex bearings  run in  vacuum (vented) .  Bearing assembly bakeout post screening performed to reduce  optical contaminants   from lubricant additives.  672 rpm  LMC 2  CH 4  80kPa  13.5 Hz  15.7 6.7E+09   rotations  Continues to operate nominally . Lost 70kPa  fill in 5 yr  810 rpm  LMC 3  CO  80kPa  11.2 Hz 15.7 5.5E+09   rotations  Continues to operate  nominally  672 rpm  LMC 4  CH4  80kPa  12.0 Hz 15.7 5.9E+09   rotations  Continues to operate  nominally  720 rpm  Scan Mirror 1        Rheolube 2000, 440C bearings with TiC-coated balls, Nylasint lubricant  reservoir  1.9 3.0E+08   steps  Unit Stopped 13-Dec2002  Failure not believed to  be mechanism related   Scan Mirror 2  15.7 2.5E+09   steps  Continues to operate  nominally  Mirrors settle in <50  ms,  stares for 400 ms per  step over ±25.2° swath  + deep space &  blackbody calibration  views ±90°  Scan Mirror 3  15.7 2.5E+09   steps  Continues to operate  nominally   Scan Mirror 4  15.7 2.5E+09   steps  Continues to operate  nominally