384 ripple) in otherwise steady torques  imparted to the RWA ring -tab-base- mount  rigid structural interface at  ratios differing from  non-spin-axis forces/moments . HST’s RWA motor  is a 2 -phase, 8- pole, brus hless  direct -current  design  with resol ver, a configuration resulting in torque ripple harmonic ratios summarized in  Table 11. Inter nal control /filtering  features are utilized to minimize  all except the 16.0 and 32. 0 harmonics.  RWA t orque ripple limits are standardly s pecified  (with margins), and precisely measured in acceptance  tests. Note that, as  verified for  HST, torque ripple IV dynamics are a negligible (i.e., nearly undetectable  analytically  or in system tests ) contributor to over all optical system LOS jitter for  all but the very lowest  frequency modes and under assum ed worst -case maximum  levels . The low torque ripple DOF  result  is due  to convergence of several favorable jitter factors :  1) electr o-magnetic origins lead  to readily -applied  circuit/ processing minimization techniques, 2) IV amplitudes are extremely low compared to other local  moment DOFs in primary  RWA operat ional  speed ranges, 3) high relative rotor inertia, 4) much higher  relative rotor structure effective stiffness  (i.e., much higher internal rotor torsional  mode frequencies ), 5)  much higher HST structural ring effective stiffness , and 6) intrinsic HST structural dynamic  mode  impediments to enable stimulating complex -compound optical paths/components to caus e LOS jitter. A lso  favorable is that tor que ripple levels are reliably  less than required limits , highly stable over time (i.e., no  significant wear source) , and not measurably affected by operating conditions or environmental changes .  Table 11.  HST RWA Spin -Axis Motor -Design -Driven Harmonic Ratios   Theory - Based  Ratio    Empirically -  Established  Ratio  Description of Root Source/Cause Sig.  Figures  Known   4.0000  4.00 COMBINED RESOLVER & ELECTRONIC DEMODULATION OFFSET WITH  OTHER EFFECTS ; DC BIAS OF EITHER SINE OR COSINE WINDING  C  AS PRECISE  AS RWA  

8.0000  8.00 ELECTRONIC GAIN MISMATCH ; MISMATCH OF SINE/COSINE WINDING  CURRENT AMPLITUDE FOR GIVEN COMMAND  AS PRECISE  AS RWA  

12.0000  12.00  ELECTRONIC NONLINEARITIES  AS PRECISE  AS RWA  

16.0000  16.00  MOTOR -RESOLVER RIPPLE ; RELATED TO WINDING  TYPE/CONSTRUCTION  AS PRECISE  AS RWA  

32.0000  32.00  MOTOR -RESOLVER RIPPLE ; RELATED TO WINDING  TYPE/CONSTRUCTION  AS PRECISE  AS RWA  

48.0000  48.00  COMBINED ROTOR -RESOLVER RIPPLE & MOTOR COGGING , DUE  PRIMARILY TO MAGNET ATTRACTION NEAR LAMINATION SLOTS  AS PRECISE  AS RWA  

96.0000  96.00  MOTOR -RESOLVER RIPPLE ; RELATED TO WINDING  TYPE/CONSTRUCTION  AS PRECISE  AS RWA      Feasibility Investigations  Validating  a Chosen  4-Harmonic  Subset  for Adequate   LOS Jitter  Assessment  

Upon thorough study  of this abundance of potential jitter error  contributors  and harmonic ratios , there  quick ly arose a huge  obstacle:  managing such a tremendous  amount of  data inputs and output assessment  summaries.  It seemed a potentially  impossible task due to so many  separate data/ combinational  elements:   • Virtually unlimited number of  individual  RWA IV frequencies to dwell at within predicted range limits   • 157 dynamic modes  (to 75Hz)  in jitter evaluations; at  practical  model/analysis  computational  limits  • 3 LOS jitter axes ; vertical, lateral, spin about  image plane centerline (HST pitch, yaw, roll)   • 5 RWAs (one spare –  but any 4 could be potentially used) ; each with its own unique IV signature   • 20 possible RWA -location permutations 5 flight -certified RWAs could be i n any of 4 flight positions   • 6 local DOF IV input force/moment  signals for each RWA ; with further breakdown as follows      20 detectable axial -force harmonic ratios applicable to 1 principal local DOF  on each RWA   28 detectable radial -force harmonic  ratios applicable to 2 principal local DOFs on each RWA