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ACS Optical Instability

ACS Optical Instability. Pam Sullivan Updated 5 July 99. 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

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ACS Optical Instability

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  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 10675 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 • Add’l 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) • Add’l 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) • Add’l 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 • Add’l 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 • Add’l 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 • Add’l 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 • Add’l Sensors: LVDTs to Monitor Motion of Bench Relative to Enclosure • Test Sequence for Baseline: • T=0 (1300GMT) ACS On/WFC TECs On • T=4 Hr HRC TEC On • T=7 Hr Chillers On • T=11 Hr Chillers Off • T=14 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 • Cube & LVDT DataIndicates Chiller Effect is (Partially?) Caused by TBF Loading the Enclosure

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