389 2) Most variations in each  RWA’s data/test -to-test differences seem to be related to  test apparat us/datagathering/data- processing/handling variances/ limitations versus  definitive trends  that clearly indicate a  detectable physical change within the RWA unit .  3) Clearly notable anomalous data points are rare (<~1%), and appears that the supplier’s computer  processing program that selects peak values for harmonics is generally functioning as -expected.   4) Significant test data variances are observed in higher harmonics at RWA rotational  speeds that place  the harmonic in proximity to the known rotor -housing resonance passage frequency.   5) Four primary axial harmonics (1.0, 2.0, 2.8, and 5.2) generally provide sufficient data for valid set -toset comparative evaluations:  other axial harmonics were either  unreliable criteria ( e.g., 0.35), or provide  too few data points in the range of  interest for conclusi ve evaluation (5.6, 7.5, and 8.5) .  6) There is no evidence of a strong correlation between overall noise data and stage- of-acceptance testing  or retesting; however, the first set of data (obtained immediately after mechanical build- up, checks,  and  fine-rebalancing)  tends to be one of the quieter  sets for any individual RWA.   7) There is no evidence of strong correlation between final rotor unbalance level (indicated by  radial force  1.0 harmonic) and overall RWA noise output /jitter (indicated by four key axial harmonics).   8) General  correlation exists between radial force and radial moment IV for the 4 key  harmonics.   9) Data obtained near any harmonic’s passage of the RWA’s internal natural resonance (~85- 90 Hz) is  commonly highly i nconsistent from dataset to dataset; also, data for other harmonics not near the  resonance range can regularly show abnormal variation due to the influence of the harmonic -passage  phenomenon (another harmonic), so should always be checked for validity/outl ier status.   10) The qualitatively noisiest overall dataset appears to be set #5 on RWA 1004; quietest overall dataset  appears to be set #1 or #3 on RWA 1003.   11) The most “typical” dataset recommended for preliminary  jitter assessment for RWA 1003 is #3.   12) The RWA 1004 2.0 harmonic data (all DOFs)  is consistently abnormally low (no known reason);  speculation is inordinately small values for imperfection in runout(s) and bearing cage roundness.   13) Overall qualitative noise rankings for HST RWAs (ordered noisiest to quietest) are:   Ranked by Force Unbalance     Ranked by Overall Noise Output       [1.0 Radial Harmonic]             [Using 4 Key Axial Harmonics]     1)  1005           1)  Tie –  1001     2)  1003           1)  Tie –  1005     3)  1001           3)  1002     4)  1002           4)  Tie –  1004     5)  1004           4)  Tie –  1003   14) Datasets chosen for most -representative- but-not-overly -quiet  (therefore as-tested, but leaning to   normal -to-high noise variance)  baseline HST jitter predictions  (e.g., investigations for isolation  properties studies) are #4 (1001), #3 (1002), #4 (1004), and #3 (1005); all are full datasets from last full  functional acceptance test runs, and have the following qualitative validity assessments:   - 1001 – no clear trend; 1.0 and 2.8 harmonics tend low, while 2.0 and 5.2 tend high.   - 1002  – tends to be somewhat higher values  overall  than average 1002 dataset   - 1004 – typical dataset   - 1005 – typical dataset  

Orbital IV Structural Dynamic  Predictive Capability Evaluations  and Results Confirmation    As discussed above, HST ground modal  test investigations , via a susp ended (stowed configuration) with  flight -like units plus mass simulators substituted  for some equipment boxes/modules , confirmed excellent  correlation between data and pretest analytical  results  for structural mode frequencies, mode shapes  /  transmissibilities, damping, and predicted known- source responses. F indings validated models required f or  dynamic l oad/clearance requirement verification (i.e., launch and ascent) and  jitter evaluation (deployed  configuration not practical to realistically ground test). Although a recommended Lockheed plan was put  forth enabling on-orbit measurements ( e.g., using a minimal set of accelerometers , largely based on  already -installed  ground test instrumentation) to  verify  HST dynamics and jitter performance, NASA chose  to not fund such efforts . The  decision was predicated upon a low and acceptable risk assessment ; wherein   existing  evidence supports that all  on-orbit disturbances are identified, accounted for , worst -case bounded,