1 acs optical instability pam sullivan updated 5 july 99

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 INNOUT

31 Mar TBF/Diamond 2465 5781411939

14 Apr Dolly/Square 488 543 2345 5781011946

2 Jun SIFIG/Aperture Down 453 603 2568 5904610675

3 Jun Dolly/Square 480 566 2568 5904910673

14 Jun Dolly/Square 477 566 2569 5904610673

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


- 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


- 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



• 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:


- Mounting: ACS in Handling Dolly in Square Orientation

- Cooling: Chillers


- 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:


- Mounting: ACS in TBF in Diamond

- Cooling: Chillers



• 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:


- 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



• 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


- Cooling: Chillers



• 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


- Cooling: Chillers



• 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


- Cooling: Chillers



• 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:



- Cooling: Chillers



• 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:



- Cooling: Chillers



• 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:



- Cooling: Chillers



• 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


- Cooling: Chillers

- Optical Source: None (ACS Off)

- Starting Temp: Ambient throughout Test (ACS Off)


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:



- Cooling: Chillers

- Optical Source: HRC Coronagraph Spot with Backlight



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:


- Mounting: In TBF/Diamond with New Linear Bearing B-Latch

- Cooling: Chillers

- Optical Source: HRC Coronagraph Spot with Backlight; WFC RAS/Cal


- 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:


- Mounting: In TBF/Diamond with New Linear Bearing B-Latch

- Cooling: Chillers

- Optical Source: HRC Coronagraph Spot with Backlight; WFC RAS/Cal


- 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

1 acs optical instability pam sullivan updated 5 july 99

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