ACS Optical Instability

1
ACS Optical Instability

• Pam Sullivan
• Updated 5 July 99

2
Instability Introduction

• Small Temperature Changes in ACS Components Cause
  Apparent Motion of All Detectors wrt Internal or
  External Optical Sources
• Specification is 10 mas peak-peak over 2 Orbits
• Several Distinct Phenomena Identified
• Warm-up Transients
• ASCS Interface Plate Related Transients
• Rolling Transients Associated with Room
  Temperature
• Shifts in Coronagraph Location with Orientation
  Change and with Different Holding Fixture

3
Coronagraph Motion w/Orientation Holding
Fixture Changes

• COR. SPOT LOCATION
• DATE CONFIGURATION X CENTER Y CENTER FOC INN OUT
• 31 Mar TBF/Diamond 2465 57814 11939
• 14 Apr Dolly/Square 488 543 2345 57810 11946
• 2 Jun SIFIG/Aperture Down 453 603 2568 59046 1067
  5
• 3 Jun Dolly/Square 480 566 2568 59049 10673
• 14 Jun Dolly/Square 477 566 2569 59046 10673

4
Instability Theories

• Troubleshooting has Confirmed that Optical Bench
  is not Isolated from Enclosure (XYZ Fittings
  should Isolate Bench)
• This Anomalous Behavior May Cause/Contribute to
  All Phenomena through the Following Mechanisms
• Enclosure Shape Change Transmits Loads to Optical
  Bench
• TBF/Dolly CTE Effects Load Enclosure which Load
  Bench
• Optical Bench CTE Expansion Results in Bench
  Bending
• Other Effects Which May be Contributing to
  Instability
• Heat Pipe CTE Expansion Imparts Loads to Optical
  Bench
• Localized CTE Effects in Detector Housings
  Other Components Expanding/Contracting CCD Heat
  Pipes Impart Load to CCDs and Optical Bench

5
Introduction to Data

• Organized Chronologically
• All Data Collected at Ambient Temperature and
  Pressure
• Optical Source was either
• RAS/Cal Point Source (External to ACS)
• Coronagraphic Spot (Internal to ACS)
• Motion is that of the Optical Source Position
  within the CCD Field of View
• Data is Presented as Delta X (Diamonds) and Y
  (Triangles) Pixels from Arbitrary Starting Point
• HRC Pixels are 21 um
• SBC Pixels are 25 um
• WFC Pixels are 15 um

6
March 22 Initial Identification of Anomaly on HRC

• Configuration
• Mounting ACS in TBF/Diamond Configuration, in
  Chamber 225
• Cooling ASCS Simulator with GN2
• Optical Source HRC RAS/Cal point source
• Starting Temp Warm, Instrument had been On for
  Several Hours
• Results
• Optical motion is correlated with cool-down of
  ASCS simulator at 1730
• Change of 7C at ASCS caused 1 pixel motion
• Note that ACS Interface Plate and CCD Housing
  cools with ASCS
• Note that Optical Bench temperature is rising
  slightly through test
• No apparent motion is seen during ASCS warm-up
• Implies anomaly is not a simple CTE
  expansion/contraction effect
• Direction of HRC motion is
• Parallel to floor, as viewed looking into
  aperture
• Side to side at the CCD, as viewed looking down
  on instrument

7
March 30 Verify Reproduce-ability Correlation
w/WFC

• Configuration
• Mounting ACS in TBF/Diamond Configuration, in
  SSDIF
• Cooling Chiller Plate
• Optical Source WFC RAS/Cal point source HRC
  Coronagraph
• Starting Temp Ambient, at Start of Day
• Results
• Little to no motion seen during ACS warm-up
• Chillers turned on to 14C causes Interface Plate
  temperature change with causes motion in both WFC
  and HRC
• In this test, a 2C delta causes 4 pixels of
  motion
• HRC moves same direction as Mar 22 data set
  (parallel to floor)
• WFC moves
• Perpendicular to floor (up and down) as viewed
  into aperture
• Fore to Aft at CCD, as viewed looking down on
  instrument

8
April 13 AM Test Effect when ACS is Suspended

• Configuration
• Mounting ACS Suspended by Crane, in TBF
  w/B-Latch Disengaged
• Cooling Chillers
• Optical Source HRC Coronagraph
• Starting Temp Ambient, at Start of Day
• Results
• Small motion seen during warm-up
• Turning chillers on to 14C causes motion
• Same direction as when latched into TBF
• Magnitude Reduced by 5X

9
April 13 PM Test Effect when ACS Held in
Dolly/Diamond

• Configuration
• Mounting ACS in Handling Dolly in Diamond
  Orientation
• Cooling Chillers
• Optical Source HRC Coronagraph
• Starting Temp Ambient, ACS off for few hours
  during relocation to dolly
• Results
• Small motion seen during instrument warm-up
• Chillers on to 14C causes noticeable transient,
  but otherwise does not seem to change warm-up
  trend
• Chillers off does not change the warm-up trend
• HRC motion is this test is different downward as
  looking into aperture

10
April 14 Test Effect when ACS Held in
Dolly/Square

• Configuration
• Mounting ACS in Handling Dolly in Square
  Orientation
• Cooling Chillers
• Optical Source HRC Coronagraph
• Starting Temp Ambient, at start of day
• Results
• Square Orientation has radiator heat pipes
  parallel to floor, and thus allows them to
  operate square is also the most
  heat-transfer-effective for the CCD heat pipes
• Turn on HRC CCD and TECs only 0.5 pixel motion
  caused during warm-up
• Turn on chillers no apparent change in warm-up
  motion trend
• Turn on WFC CCDs and TECs causes small slope
  increase in warm-up trend
• Turning off chillers changed the direction of the
  motion trend

11
April 15 AM Compare Dolly/Diamond Motion when
HPs Disconnected

• Configuration
• ACS CCD Heat Pipes Disconnected at IF Plate
• Mounting ACS in Handling Dolly in Diamond
  Orientation
• Cooling Chillers
• Optical Source HRC Coronagraph
• Starting Temp Ambient, at start of day
• Results
• Note data noisy due to operating CCDs at room
  temperature (TEC off)
• Small motion 0.5 pixel seen during warm-up
• Motion perpendicular to that seen in
  dolly/diamond with HP connected
• Chillers turned on to 14C caused no correlated
  motion
• Note large jump at 17.3 most likely due to
  optical source change

12
April 15 PM Compare Dolly/Square Motion when HPs
Disconnected

• Configuration
• ACS CCD Heat Pipes Disconnected at IF Plate
• Mounting ACS in Handling Dolly in Square
  Orientation
• Cooling Chillers
• Optical Source HRC Coronagraph
• Starting Temp Warm after several hours of
  Operation
• Results
• Note data noisy due to operating CCDs at room
  temperature (TEC off)
• Start warm with chillers on at 14C
• No apparent motion due to turning chillers off
• Turning HRC TEC on at 21.9 causes a large jump
  due to image quality improvement (not a
  thermal-mechanical effect)
• Correlation between motion TEC on/off state
  identified (due to Housing temp?)
• Turning HRC TEC off at 22.7 causes small 0.3
  pixel motion
• Turning HRC TEC on at 23.0 causes TEC-off motion
  to reverse

13
April 16 Compare TBF/Diamond Motion when HPs
Disconnected

• Configuration
• ACS CCD Heat Pipes Disconnected at IF Plate
• Mounting ACS in TBF in Diamond
• Cooling Chillers
• Optical Source HRC Coronagraph
• Starting Temp Ambient, at start of day
• Results
• Warm-up effect of 1.5 pixels seen
• Direction of motion similar to that with heat
  pipes connected
• Chillers-on seemed to restart warm-up trend which
  had stalled for 15 minutes
• Chillers off had no apparent effect
• Motion correlated with TEC on/TEC off repeated

14
May 7 Measure Thermal Stability Effect on SBC

• Configuration
• ACS Fully Assembled
• Mounting ACS in TBF in Diamond
• Cooling Chillers
• Optical Source SBC RAS/Cal Point Source in N2
  Purge
• Starting Temp Close to Ambient after being off
  for Lunch
• Results
• Warm-up effect of 1 pixel seen
• Chillers-on caused motion of 4-5 pixels
• Motion is different than HRC effect
• Indicates that effect is not solely M1 or M2
  motion
• Chillers off reversed the chillers-on effect
• WFC TECs off/on had no effect on warm-up or
  chiller trend

15
June 2 Measure Stability with Aperture
Down/Y-Fitting Free

• Configuration
• ACS Fully Assembled
• Mounting ACS attached to SIFIG by GSE Lifting
  Points
• ACS Clocked 10 deg off Vertical, Aperture
  Facing Floor
• Note This Configuration Frees Y-Fitting but
  also Precludes HRC Heat Pipes from Transferring
  Heat to ASCS Plate
• Cooling Chillers
• Optical Source HRC Coronagraph Backlight
• Addl Sensors Displacement Sensors Measuring
  Latch Motion Theodolites Measuring In Plane
  Motion of IF Plate and Radiator Panel Relative
  to P2 Enclosure Panel
• Starting Temp Ambient at Start of Day
• Results
• Warm-up effect barely present at 0.1 pixel
• Chillers-on Caused no Perceptible Change in
  Warm-up Trend
• HRC TECs Off (to Prevent Safing due to Overtemp
  Housing) Caused Drift Effect which is Not Related
  to Stability Effect
• No Measurable Motion seen by Displacement or
  Angular Sensors (sensitivity is .0001 inch)

16
June 3 Measure Stability with Radiator Panel
Unbolted

• Configuration
• ACS P2 Radiator Panel Bolts Loosened 1 Turn
• Mounting In Dolly, in Square with Radiator
  Facing Up Parallel to Floor
• Cooling Chillers
• Optical Source HRC Coronagraph Backlight
• Starting Temp Ambient at Start of Day
• Results
• Warm-up Effect of 1 pixel seen
• Chillers-On Off had No Effect
• HRC Set Point Change from -90C to -67C Caused
  Noticeable Slope Change
• New Rolling Effect in X-Axis only Started
  without Apparent Cause 7 Hours Into Test and
  Continued through Remaining 8 Hours
• Also Noticed an Unexplained Increase in Noise in
  Spot Location Data as Test Progressed
• There was No Corresponding Increase in Image Noise

17
June 4 Measure Stability with Radiator Panel
Rebolted

• Configuration
• ACS Assembled with Panel Bolts Re-Tightened
• Mounting In Dolly, in Square with Radiator
  Facing Up Parallel to Floor
• Cooling Chillers
• Optical Source HRC Coronagraph Backlight
• Starting Temp Ambient at Start of Day
• Results
• Executed Test Sequence Identical to Previous Day
  for Apples-Apples Comparison
• Resulting Pixel Motion Nearly Identical to
  Previous Day, Except
• Warm-up Effect Barely Present
• Possibly because ACS Started 1C Warmer?
• Possibly because Enclosure is More Resistant to
  Shape Changes with Panel?
• HRC Set Point Change Caused Slope Change
• This Effect Probably Occurred Yesterday but was
  Masked by Warm-up Effect
• Rolling Effect Larger Magnitude
• Rolling Appears Correlated with JIN2PANT
  Enclosure Panel Temperature
• Except for Rolling, Stability is Better with
  Enclosure Panel Bolts Torqued

18
June 7 Test Rolling Effect Theories

• Configuration
• ACS Assembled
• Mounting In Dolly, in Square with Radiator
  Facing Up Parallel to Floor
• Cooling Chillers
• Optical Source HRC Coronagraph Backlight
• Starting Temp Ambient at Start of Day
• Results
• Rolling was Correlated with Enclosure Panel Temp
• Heat from 650W Lamp Used to Change Enclosure
  Panel Temperature
• Applying Heat to O3 and O2 (Separately) Caused
  Apparent Motion in Y-Axis Only
• Previous Rolling was in X-Axis Only
• Imaging Interval Varied (30 min imaging, 5 min
  break, 30 min imaging, 10 minute break, 30 min
  imaging, 15 min break) to Determine if Breaks
  Causes Cooling
• Conclusion
• Rolling is not Caused by Enclosure Panel Heating
  nor Imaging Operations

19
June 9 Relieve Heat Pipe Installation Stress
Loosen ASCS Bolts

• Configuration
• ACS ASCS Plate Bolts to Radiator Panel Loosened
• Mounting In Dolly, in Square with Radiator
  Facing Up Parallel to Floor
• Cooling Chillers
• Optical Source HRC Coronagraph Backlight
• Starting Temp Ambient at Start of Day
• Results
• No Warm-up Effect Seen
• No Chillers-On or Off Effect Seen
• Changing HRC Set Point to -85C Apparently Caused
  Motion in X
• Changing HRC Set Point back to -67C Produced
  Motion in Y, but did Not Reverse Y Trend

20
June 10 Re-Bolt ASCS Interface Plate

• Configuration
• ACS Fully Assembled
• Mounting In Dolly, in Square with Radiator
  Facing Up Parallel to Floor
• Cooling Chillers
• Optical Source HRC Coronagraph Backlight
• Starting Temp Ambient at Start of Day
• Results
• No Warm-up Effect Seen
• No Chillers-On Effect Seen
• Chillers Off Caused 0.3 pix/hr Motion in Both
  Axes
• Changing HRC Set Point had No Effect
• Conclusion
• No Significant Difference between ASCS IF Plate
  Loose vs Bolted

21
June 11 Monitor Stability w/o Changing Detector
or Chiller State

• Configuration
• ACS Fully Assembled
• Mounting In Dolly, in Square with Radiator
  Facing Up Parallel to Floor
• Cooling Chillers
• Optical Source HRC Coronagraph Backlight
• Starting Temp Ambient at Start of Day
• Results
• Warmup and/or Chiller Effect seen for 7 Hours
• Pixel Location Stabilizes for 1 Hours at End of
  Data Collection

22
June 14 Monitor Stability w/Room Temperature
Change

• Configuration
• ACS Fully Assembled
• Mounting In Dolly, in Square with Radiator
  Facing Up Parallel to Floor
• Cooling Chillers
• Optical Source HRC Coronagraph Backlight
• Starting Temp Ambient at Start of Day
• Results
• Warm-up and/or Chiller Effect seen for 4 Hours
  at Start of Day
• Stability after 1700GMT Correlates with JO3APANT
  Enclosure Panel Temperature Enclosure Panel
  Correlates Grossly with Room Temperature
• Conclusion
• Stability is Correlated with Room Temperature
• Potential Mechanism is Dolly Length Change with
  Temperature Loads Enclosure

23
June 17 Compression Test to Verify Presence of
Y-Fitting Stiction

• Configuration
• ACS Fully Assembled OFF for this Test to
  Eliminate Thermal Effects
• Mounting In TBF/Diamond
• Cooling Chillers
• Optical Source None (ACS Off)
• Starting Temp Ambient throughout Test (ACS Off)
• Addl Sensors LVDTs to Monitor Motion of Bench
  Relative to Enclosure Theodolites to
  Monitor TBF and ACS Optical Cube Motion
• Results
• TBF B-Latch Used to Compress Enclosure from 0 to
  800lb in 50lb Increments
• Increasing Load Compresses Both Enclosure
  Optical Bench by 25 mil
• ACS Optical Cubes Motion of 6 to 18 as
  Indicates Bench is Bending w/Increasing Load
• Conclusion
• Optical Bench Moves with Enclosure
• Y-Fitting is not Behaving per Design

24
June 18 Repeat Compression Test for Repeatability

• Configuration
• ACS Fully Assembled OFF for this Test to
  Eliminate Thermal Effects
• Mounting In TBF/Diamond
• Cooling Chillers
• Optical Source None (ACS Off)
• Starting Temp Ambient throughout Test (ACS Off)
• Addl Sensors LVDTs to Monitor Motion of Bench
  Relative to Enclosure Theodolites to
  Monitor TBF and ACS Optical Cube Motion
• Results
• Decompression Reverses Compression Effect with
  Little or No Hysteresis
• Compression and Decompression Effects are
  Repeatable
• Conclusion
• Optical Bench Moves with Enclosure
• Y-Fitting is not Behaving per Design

25
June 21 AM Compression Test with ACS On to
Correlate Spot Motion

• Configuration
• ACS Fully Assembled
• Mounting In TBF/Diamond
• Cooling Chillers
• Optical Source HRC Coronagraph Spot with
  Backlight
• Starting Temp Ambient at Start of Day
• Addl Sensors LVDTs to Monitor Motion of Bench
  Relative to Enclosure Theodolites to
  Monitor TBF and ACS Optical Cube Motion
• Results
• TBF B-Latch Used to Compress/Decompress Enclosure
• Both Enclosure Bench Move with Changing Load
• Coronagraph Moves 7 Pixels in Each Axis with
  Changing Load
• Compression Effect is Repeatable Decompression
  is Repeatable
• Compression vs Decompression Motion Shows
  Hysteresis
• Conclusion
• Coronagraph Motion is Correlated with
  Enclosure/Bench Motion and is thus Caused (at
  least in part) by Stuck Y-Fitting

26
June 21 PM Compression Test with ACS On to
Correlate Spot Motion

• Configuration
• ACS Fully Assembled
• Mounting In TBF/Diamond
• Cooling Chillers
• Optical Source SBC Coronagraph Spot with
  Backlight
• Starting Temp Warm after Morning Operations
• Addl Sensors LVDTs to Monitor Motion of Bench
  Relative to Enclosure Theodolites to
  Monitor TBF and ACS Optical Cube Motion
• Results
• TBF B-Latch Used to Compress/Decompress Enclosure
• Both Enclosure Bench Move with Changing Load
• Coronagraph Moves with Changing Load
• Compression vs Decompression Motion Show
  Hysteresis
• SBC Motion is Nearly Identical to HRC Magnitude
  and Direction
• Conclusion
• Coronagraph Motion is Correlated with
  Enclosure/Bench Motion and is thus Caused (at
  least in part) by Stuck Y-Fitting
• Similarity of SBC HRC Motion Indicate Effect is
  Predominately Motion of the M2 Mirror

27
June 23 Aborted Baseline TBF Temperature
Change Test

• Configuration
• ACS Fully Assembled
• Mounting In TBF/Diamond with New Linear Bearing
  B-Latch
• Cooling Chillers
• Optical Source HRC Coronagraph Spot with
  Backlight WFC RAS/Cal
• Starting Temp Ambient at Start of Day
• Addl Sensors LVDTs to Monitor Motion of Bench
  Relative to Enclosure
• Results
• Had Planned to Run Long Duration Baseline for
  Comparison to RASHOMS Results
• WFC Over-Temp Forced WFC TECs to be Turned Off
  Baseline Aborted
• Temp Change of TBF Bottom Support Post (20 to 30
  to 20C) Caused WFC HRC Motion
• Temp Change of V2 Support Post (20 to 30 to 20C)
  Caused WFC HRC Motion
• During Temp Changes B-Latch Load Cell Measured
  Changing Load (30lb) and LVDTs Measured Motion
  of Enclosure Bench Relative to TBF
• Conclusion
• TBF Temp Changes Causes TBF Length Change Causes
  Load Change Causes Enclosure/Bench Motion
• Y-Fitting Stiction Prevents Verification of
  Proper B-Latch Motion

28
June 24 Baseline Stability in TBF for
Comparison to RASHOMS

• Configuration
• ACS Fully Assembled
• Mounting In TBF/Diamond with New Linear Bearing
  B-Latch
• Cooling Chillers
• Optical Source HRC Coronagraph Spot with
  Backlight WFC RAS/Cal
• Starting Temp Ambient at Start of Day
• Addl Sensors LVDTs to Monitor Motion of Bench
  Relative to Enclosure
• Test Sequence for Baseline
• T0 (1300GMT) ACS On/WFC TECs On
• T4 Hr HRC TEC On
• T7 Hr Chillers On
• T11 Hr Chillers Off
• T14 Hr Test End
• Results
• Warmup and Chillers On Effects Present at 0.5
  pixels Chillers Off Effect Present at 1 pixel
• TBF Cube Motion of 8 as and AC1 Motion of 3 as
  Observed During Chillers On (Optical Cube Data
  was Taken Only During the Chillers On Segment
  from1540-1800)
• LVDTs Show Small TBF Expansion Correlated
  w/Chillers On Off