Date post: | 01-Jan-2016 |
Category: |
Documents |
Upload: | allyson-miles |
View: | 213 times |
Download: | 0 times |
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
- 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