UVIT NUV Engineering Model Detector Calibration Plan
Joe Postma
John Hutchings
Revision Number: 05
Date: Oct 31, 2008
The following is a list of calibration tests planned for the engineering model detector (EM) to be
carried out at the Calibration Lab at the University of Calgary. The primary motivations for the EM
calibration are to:
1) Understand how to run the detector and ground support equipment (GSE)
2) Understand safety aspects of running the detectors.
3) Understand the data output and how to handle it.
4) Understand the overhead in setup and data-gathering time for each test.
5) Develop an understanding of post-data-gathering tasks.
6) Establish contamination control process and standards.
7) Develop an efficient and effective flight model (FM) calibration plan, particularly in terms of
time required, priority, and a schedule.
Definitions:
BOD: Bright Object Detect
Centroiding Element: Square fraction of a pixel, determined by the centroiding resolution, ex. 1/8th or
1/16th of a pixel (squared) for 8X or 16X centroiding respectively.
EM: Engineering Model detector.
FM: Flight Model detector or spare.
Pixel: Is a single 25um x 25um pixel of the Star250 chip.
List of Tests: (expanded and described below)
1) Darks: No light source, explore back ground effects, etc
2) Flat Fields: Spatial sensitivity variations, geometric distortions, fixed pattern noise, read rate
testing
3) Spot Array: Geometric distortions, read rate testing
4) Moving Spot: Simulate spacecraft drift (not a priority)
5) Large Spot: Extended object simulation
6) Bright Object Detect: Bright object detection algorithm testing
7) Small Window: Fast read rate testing
8) Integrate Mode: Dark current rates, resolution, flat field
9) Spectrum: Simulate gratings (not a priority/not being done)
10) MCP Voltage Gain: Characterize at various levels
Note: Temperature tests currently not possible in Calgary for EM
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1. Darks
a. Motivation:
i. Check for dead or hot pixels, and/or hot MCP pores
ii. Explore cosmic ray effects - i.e., rates, energy distribution, event profiles
iii. Determine bias levels and dark current rate, vs. temperature if possible
b. Signal Level: bias/dark only (no signal)
c. Tank Setup: sealed from all possible light sources
d. Settings: Several temperatures, if possible. Full frame and small window fast read.
Spread over the calibration timeframe.
e. Data Quantity: 10000 reads per test. 3 temps and 3 read rates (i.e. windowing modes)
each. Also integrate mode tests with 0.1s to 5s exposures.
f. Time Required: Setup time minimal; data collection time 1-3 hours, depending on
temperature control and number of tests (8 hours?).
g. Post Processing: Analysis of count rates and images from count mode. Set up table of
hot pixels. Look for time changes.
2
2. Flat Field
a. Motivation:
i. To characterize fixed pattern noise and calibrate centroiding-correction
algorithms (count mode)
ii. To determine areal sensitivity variations (count mode and integrate mode)
iii. Explore sensitivity vs. wavelength.
b. Signal Level: 1000 counts per pixel (post reduction level for integrate mode),
c. Tank Setup: UV source on, monochromater for wavelength variation.
d. Settings: Several wavelengths, several light levels, up to maximum count rate. More
than one temp desirable.
e. Data Quantity: 3 photon rates and 6(?) wavelengths. Sub-window reads.
f. Time Required: Depends on light levels, QE, etc. 16 hours?
g. Post Processing: Image analysis, fixed pattern noise correction algorithm calibrations,
etc.
3
3. Spot Array
a. Motivation:
i. To determine geometric distortions and PSF resolution (count mode).
ii. To calibrate algorithm point-source counting rates and explore count rate limits.
iii. Test centroid-correction algorithms.
b. Signal Level: 1000 counts spot maximum per pixel. Brightest spot at 0.5 counts per
frame. 10 counts on faintest spot.
c. Tank Setup: UV source, spot mask, focus spots, move detector platform between
integrations.
d. Settings: Large spot mask, several photon rates, several wavelengths, several detector
positions. Spot size can be smaller than pixel or pixel size. Number and freq TBD.
e. Data Quantity: Need several positions to cover the full detector window. 2 photon
rates, 1 wavelength, more than one temp desired
f. Time Required: Depends on light level, focusing time, permutations, etc, 16 hours?
g. Post Processing: Image analysis, PSF fitting, create distortion map from known spot
geometry.
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4. Moving Spot
a. Motivation: To simulate spacecraft drift and imaging effects thereof, i.e. putting a point
source back together.
b. Signal level: TBD to mimic real obs.
c. Tank Setup: Large spot mask. Focused spots. Moving manipulator. Rates to bracket
expected drift rates.
d. Settings: Several rates of movement, single wavelength, single intensity
e. Data Quantity: TBD
f. Time Required: 8 hours?
g. Post Processing: shift and add in assembling image.
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5. Large Spot
a. Motivation:
i. To simulate extended objects such as galaxies/nebulae.
ii. To calibrate algorithm extended-source counting rates and establish count rate
limits.
iii. Test centroid-correction algorithms.
b. Signal Level: 1000 counts per pixel max
c. Tank Setup: Out-of-focus spot(s). Light level maximum 0.5 events per pixel per frame.
d. Settings: 2 wavelengths?, several photon rates?
e. Data Quantity: TBD
f. Time Required: 16 hours?
g. Post Processing: Image analysis, centroiding algorithms, thresholds, etc
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6. Bright Object Detect(already verified during Routes testing, Feb. 2008)
a. Motivation:
i. Test bright object detection
ii. Determine bright threshold rates
iii. Calibrate photometric linearity for different photon rates.
iv. Explore charge leakage behaviour from saturated pixels
b. Signal Level: TBD
c. Tank Setup: single focused spot, variable brightness, calibrated apertures for light flux,
flux monitor, also flat field
d. Settings: Single wavelength, various photon rates via apertures.
e. Data Quantity: TBD
f. Time Required: 8 hours?
g. Post Processing: images with different thresholds, photometric calibration, light level
where BOD sets in.
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7. Small Window Spot(s)
a. Motivation:
i. Test higher photon rates than at 29Hz and determine imaging rates at various
windows sizes
b. Signal Level: TBD
c. Tank Setup: single focused spot or spot mask
d. Setting: 5(?) photon rates, 3(?) window sizes (& read rates)
e. Data Quantity: TBD
f. Time Required: 16 hours?
g. Post Processing: Image analysis
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8. Integrate Mode
a. Motivation:
i. determine background noise with integrate time i.e., the dark current rate.
ii. measure PSF’s, resolution
iii. photometric calibration
iv. determine variations in gain and flat field with different MCP HV settings
b. Signal Levels: Up to bright object limit
c. Tank Setup: Multiple spot mask, focused, range of temperatures. Flux monitor. Likely
run as extension of photon counting tests where setup is the same.
d. Settings: 4 photon rates, 3 integrate intervals, more than one temp
e. Data Quantity: TBD
f. Time Required: 16 hours(?)
g. Processing: Accumulate images, remove dark noise, centroid spots
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9. Spectrum (in lieu of gratings and filter wheel for FM)
a. Motivation:
i. Calibrate response with wavelength.
b. Signal Levels: high and low for S/N estimation
c. Tank Setup: TBD, monochromater
d. Settings: TBD, 2 photon rates
e. Data Quantity: TBD
f. Time Required: TBD
g. Processing: Accumulate spectrum, measure S/N, photometric calibration(?)
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10. MCP Voltage Gain
a. Motivation:
i. Test low gain operation
b. Calibrate at chosen voltage(s)
c. Signal Levels: high (but need to check BOD in this mode) 1 count per second at max
hole to start.
d. Tank Setup: Single spot focused, flux monitor
e. Settings: Drop MCP voltage to several values with output about 10% of normal. Raise
light level to several higher values.
f. Data Quantity: TBD
g. Time Required: 8 hours
h. Processing: Generate images, calibrate gain, PSF, photometric calibration.
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Logistical Priority Scheduling
Calibration tasks are listed as “Procedures”, due to the general uncertainty of task timings, and are listed
in temporal priority.
Definitions:
BMU: Bus Management Unit
BOD: Bright Object Detect
CPU: Camera Proximity Unit
DHU: Data Handling Unit
Dump Segment:
Functionality of DHU which outputs to text file a single segment of data (2048
bytes, 1024 words) at a specified segment number from the selected *.img file.
ESD: Electrostatic Discharge.
EU:
Electronics Unit.
GSE: Ground Support Equipment; the entirety of components which run the CPU and HVU and
provide data output and interactivity for ground calibration purposes.
HV:
High Vacuum (~10^-7 Torr in Main Chamber, ~10^-5 in UV Arm)
HVU: High Voltage Unit.
HVU OFF:
The HVU voltages are all set to zero.
PCU: Power Control Unit
RN:
Read Noise.
Sync Report: Functionality of DHU which scans *.img files for loss of segment synchronization word
sequence: 0x1ACF, 0xFC1D. For verifying file integrity.
QV:
Quick View functionality of DHU, for viewing single images stored within integration or centroid
mode *.img data files.
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Calibration Procedures (expanded below)
Preliminary Setup and System Verification Tasks:
1. *System Arrival and Setup
2. Initial System Startup: HVU OFF
3. *Initial System Startup: HVU ON
4. *High Vacuum Pump Down
5. *High Vacuum Initial Performance Confirmation:
HVU ON
Preliminary Laboratory Tasks:
6. *UV Light Source Characterization, Direct Illumination: HVU ON
Detector Calibration Tasks:
7. Dark Field Characterization: Read Rates, Dark Current, Gap Time, Cosmic Rates
8. Flat Field: BOD
9. Flat Field: Star250 Reset Bias Voltage, Star250 Gain, Non-Zero Gap Time, Stacking & Normalizing
10. Flat Field: MCP Voltage Calibration – Nominal, Count Rate Linearity, Sub Window, Fixed Pattern
Noise, Low MCP Gain with Star250 Gain
11. Flat Field: Wavelength Characterization
Preliminary Laboratory Tasks:
12. *HV System Cycle: Insert Spot-Focusing Optics
13. *Point Source Mask: Optical System Characterization
Detector Calibration Tasks:
14. Point Source Mask: MCP Voltage Calibration – Nominal, Low MCP Gain, Count Rate Linearity,
Sub Windows, Geometric Distortion, Wavelength Characterization
15. Point Source Mask: Supplementary Geometric Distortion Characterization - Low MCP Gain with
Star250 Gain 2 at Low, Mid and High Flux, 5 MCP Voltages at 2 Flux Levels (high saturation and
low/no saturation)
16. Point Source Mask: Large Spot – Count Rate Linearity Characterization
17. Point Source Mask: Moving Spot
Note: * indicates procedures in which the data taken is not relevant to EM Calibration and for
subsequent analysis. It is only for equipment testing and system verification proposes.
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Preliminary Setup and System Verification Tasks:
1. System Arrival and Setup
a. Unpacking and temporary storage of components
i. ESD and clean sensitive materials (CPU, EU?, etc) placed in clean enclosure with
ESD protection (ESD mats, humidity, ESD handling, etc).
ii. GSE placed in position for connection to HV tank, outside clean enclosure.
b. CPU dust cover left ON for initial system startup and testing.
c. CPU and HVU placed inside HV tank and mounted onto manipulator.
d. Cable connections made to tank flange and HVU/CPU.
e. Cables secured, placed for manipulator clearance.
f. Manipulator clearance and range of movement tested. Manipulator common positions
recorded.
g. HV Tank sealed
i. CPU dust cover left ON
ii. Tank lid secured
iii. Viewing ports covered
Estimated Time: One working day – 8 hours
Ready for initial operational performance testing.
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2. Initial System Startup: HVU OFF
a. HVU OFF: This means that the EU to HVU cable is UNNATACHED.
b. Turn on GSE computer systems, confirm telemetry systems are functional and
communicating
i. Observe PCU and BMU telemetry windows, confirm connectivity.
c. Confirm DHU is functional by taking Dark imaging runs
i. Tank Viewing ports can be uncovered and room lights on, as HVU is off.
ii. Integration Mode:
1. This is to give Star250 baseline reference.
2. Image for 30 minutes.
3. View images with QV
a. Images should show bias level.
iii. Centroid Mode:
1. This will allow quick view (with CCDLAB software) of image run to
determine if any spurious events or signals were picked up by the
centroiding algorithms.
2. Image for 30 minutes.
3. View Images with QV
a. Images should be black (empty); this possibly dependant on
threshold settings – if low enough will centroid noise
b. 3x3 Cross only
Estimated Time: 1 hours
GSE and detector systems initial functionality and connectivity confirmed.
Ready to test HVU operational performance in ATMO.
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3. Initial System Startup: HVU ON
a. Confirm HV tank viewing ports are covered and light sources are extinguished.
b. CPU cover ON. – Note Nov 06, 2008: Due to design of CPU jig and CPU front cover,
CPU front cover must be removed for mounting to jig. CPU cover OFF.
c. Confirm System in LOW POWER state or OFF.
d. Allow a light leak into the HV tank: Fully uncover a SINGLE viewport with Room Lights
Off.
i. Expect possible small count rate due to photon leakage around CPU front cover
gasket. May see nothing at all if light level low/photon leakage low.
e. Confirm system integrity by taking several Low Light imaging runs with HVU at nominal
recommended operating voltages.
i. Use safe BOD settings
1. Length = 3 pixels; Height = 6000 ADU; Frames = 3 frames
2. Detector will BOD as voltages ramp up if light level too high
a. Adjust light level as necessary by covering viewing ports
ii. Integration Mode:
1. View images with QV
a. Images should show events only within taper region; number of
events dependant on light leakage level.
b. If light is leaking into the CPU enclosure, will see light around
the fiber optic taper. This is not expected.
iii. Centroid Mode:
1. View Images with QV
a. Images should only show events within taper region; number of
events dependant on both threshold settings and light level.
b. If light is leaking into CPU enclosure, will also see events around
the fiber optic taper. This is not expected.
f. RE-COVER HV tank viewing ports.
Estimated Time: 1 Hours
GSE and Detector Systems now confirmed operational with HV in ATMO.
Ready for vacuum testing.
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4. High Vacuum Pump Down
a. Entire GSE system OFF
b. Re-open HV tank lid
c. Place single pinhole optics in UV arm optical path (for flat fielding)
d. Remove CPU dust cover
e. Close HV tank lid
f. HVU TO REMAIN OFF until high vacuum (~10^-7 Torr on main tank) reached and
soaked for 3 hours – HVU discharge arcing and destruction can occur at low (i.e., not
high or ultra [or atmosphere]) vacuum pressures.
g. HVU box must be <10^-5 Torr for operation
h. Begin HV pump down
i. Evacuate UV arm and main chamber
ii. ~24 hours for nominal (empty, clean tank) pump down to ~10^-7 Torr.
i. RGA
i. Perform Residual Gas Analysis of main chamber when main chamber B-A
Gauges begin to read ~10^-6 Torr.
1. Record RGA profile
a. Will have RGA profile from before tank vacuum was last broken
for comparison
Estimated Time: 24 – 48 Hours
When operating detector system at high vacuum, ensure Bayard Alpert and RGA vacuum gauges are
turned OFF as these emit large amounts of light into the main chamber. Always remember to turn the
B-A and RGA gauges OFF after periodically checking the main tank and UV arm vacuum pressures.
Never operate the HVU/CPU with the vacuum ion gauges turned on.
Always turn off the UV light source when the detector system is not imaging, so as to not overexpose
the photocathode. Leaving it on even for a few minutes between imaging runs can cause ESD build up
on the detector, and may also modify the areal sensitivity of the photocathode.
UV source also has limited lifetime (~2000 hours), so conservation is important.
UV optics also degrade with time of exposure to UV light, extremely so when not at high vacuum. UV
Source should NEVER be turned on above 10^-5 Torr.
UV Arm vacuum must be order 10^-5 Torr or less for operating UV source. Damage may occur to optics
if turned on above this level.
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5. High Vacuum Initial Performance Confirmation:
HVU ON
a. Main Tank vacuum ~10^-7 Torr
b. UV Arm vacuum ~10^-5 Torr
c. Room lights OFF.
d. Vacuum tank viewing ports are COVERED.
e. All light sources extinguished.
f. Confirm DS is functional by taking a 5 minute Dark imaging run
i. Integration Mode (only, sufficient for operational verification)
1. QV several images to confirm operational.
a. Should see bias level
ii. If photon events are present, determine light leak(s), fix them, and repeat.
1. Background Cosmic rate expected: Cosmic Rate = TBD
GSE and Detector Systems now confirmed operational in VACUUM.
Estimated Time: 1 hour
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Preliminary Laboratory Tasks:
6. UV Light Source Characterization, Direct Illumination: HVU ON
a. System at high vacuum
b. Grating position should be at 230nm
c. Initial iris position should be set to minimum throughput stop, and then off-set to
reduce photometer count rate to initially ~1000 counts/s.
d. Orient Manipulator so CPU is facing and on axis with optical source
i. Use pre-saved manipulator position setting
ii. Observe manipulator movement through viewport; expect this motion to be
safe. Re-cover viewport when finished.
e. Prepare HVU ON imaging integration run setup in GSE
i. Use safe BOD settings
1. Length = 3 pixels; Height = 6000 ADU; Frames = 3 frames
ii. Use nominal recommended operating voltages
iii. Centroid mode only to quickly get count rate from Quick View
b. Strike UV lamp
i. UV Lamp requires 60 seconds to ignite after strike
c. After UV lamp ignites, begin imaging
i. Begin imaging after light source ignited so that DS can BOD during voltage rampup period if necessary, to protect the CPU
d. Image for ~60 seconds after voltages fully ramped
f. If BOD, Turn OFF UV source
i.
Record lab photometer count rate and iris setting
ii.
Use smaller UV mono iris setting
iii.
Stop imaging and repeat this entire activity
g. Turn OFF UV source
i.
Always turn off when not in use so that photocathode is not overexposed.
h. Examine *.img file for UV source events
i.
Should see at least see a few events, perhaps very many
ii.
This is to give the user some familiarization with the UV light source
brightness
i. Characterize reference photometer count rate vs. DS count rate
i. Optimize event count by adjusting UV mono iris position
i.
Try to attain ~<500 hundred counts/frame at 230nm direct illumination
ii.
Vary iris position and determine spot count rate vs. reference photometer
iii.
Record iris position, grating position (230nm), and count rates of lab
photometer and CPU.
a. Relationship will be different at different wavelengths, but this will
give a rough estimate. May need to widen spectrometer entrance slit
to allow more wavelength through
Estimated Time: 6 Hours
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Optical System now characterized. Ready to begin Detector Calibration Procedures. System at high
vacuum.
20
Detector Calibration Tasks:
7. Dark Field Characterization: Read Rates, Dark Current, Gap Time, Cosmic Rates
a. System at high vacuum
b. All HV tank viewports covered
c. All light sources off (B-A, RGA and thermocouple Gauges, UV source)
d. EMI sources off (vacuum measurement electronics, photometer)
e. Use safe BOD settings
i. Length = 3 pixels; Height = 6000 ADU; Frames = 3 frames
f. Use nominal recommended operating voltages (when HVU required)
g. HVU OFF: Read Rates, Gap Time, Dark Current
i. Expect NO events - possibly cosmic hits
ii. Integration Mode only
iii. Read Rate Characterization at zero Gap Time
1. Full Frame; Sub Windows: symmetric, asymmetric and opposites
2. 10 symmetric window sizes, 5 pairs of asymmetric/opposite window
sizes
3. Require only ~5 minutes, or two *.img files, of data
4. Determine “delta” row-read-time from this data
a. Presumably independent of number of columns (YSIZE), but a
function of row width (XSIZE)
iv. Read Rate Characterization at non-zero Gap Time: dark current
1. Full Frame; 2 Sub Windows
2. 7 integration times: 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 and 1.4 seconds
3. Total Integration Time determined by:
a. TIT = (gap_time + delta)*512
b. Gap Time is the user-settable parameter in the GSE
h. HVU ON: Cosmic Rates
i. Full Frame, zero gap time
ii. Use nominal HVU voltages
iii. Integration Mode
1. Image for 30 minutes
iv. Centroid Mode
1. Image for 30 minutes, 3x3 Square algorithm only
Estimated Time: 8 hours total
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8. Flat Field: BOD
a. This functionality has been tested and confirmed at Routes. Perform nominal
confirmation at ~500counts/sec with low BOD thresholds only.
b. System at high vacuum
c. Centroiding Mode
d. BOD triggers on the realization of three criteria:
i. Length: number of adjacent pixels which exceed the “Height”
ii. Height: the ADU count of the pixel(s)
iii. Frames: the number of frames, in sequence, which satisfy the “Length” and
“Height” criteria
e. Use default nominal operating voltages for this test
i. Cathode = -400V
ii. MCP = 2020V
iii. Anode = 5000V
f. A true “bright object” in flat field illumination would imply a much too high flux across
the entire detector
i. Therefore do not truly want to expose the detector to dangerous light levels,
and so will test BOD at normal operating light levels
Estimated Time: 4 Hours
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9. Flat Field: Star250 Reset Bias Voltage, Gain, Non-Zero Gap Time, Stacking & Normalizing
a. Rest voltage must be optimized before continuing beyond this task
i. PHD’s, FWHM’s, and RN significantly affected by these values
b. HV Tank ~10^-7 Torr, UV Arm ~10^-5 Torr
c. CPU oriented in line with light source
d. UV mono at 230nm
e. Iris positioned for count rate ~100-500 hundred/frame
f. Use safe BOD settings
i. Length = 3 pixels; Height = 6000 ADU; Frames = 3 frames
g. Integration Mode imaging only for voltage calibration (not possible to calibrate voltage
in Centroiding Mode)
h. Turn OFF UV Source between voltage variation imaging runs
i. Always turn off when not in use so that photocathode is not overexposed
ii. Always begin imaging only after UV source is ignited to ensure BOD functionality
i. Star250 Reset Bias Voltage Characterization
i. Use nominal HVU voltages for characterizing this behaviour
ii. Valid Reset Bias voltage values are between 3 and 5 Volts
1. 5 volts is “soft”: allows fading events
2. 3 volts is “hard”: supposed to suppress fading events, but testing at
Routes has shown severe distortion of event profiles at this voltage
3. Characterize between 3 and 5 volts in 0.25 volt increments
4. Require ~5 minutes of imaging at 500c/s in order to explore event
profile/FWHM, PHD, RN, and fading event response to voltage value
change
iii. Optimize this voltage before continuing to any next task.
1. Presumably will be 5 volts, based on previous data results at Routes
j. Gain Characterization
i. Characterize first with HVU Off dark frames.
ii. Valid Gain settings likely to be only ONE (default) or TWO, given energy of
events (max = 9000) and saturation level of ADC (14 bit = 16384)
iii. Once dark frame behaviour is known, then illuminate DS using nominal HVU
voltages
iv. May need to adjust BOD
v. Can asses if lowered MCP voltage/high Star250 gain tests are required in next
section after consultation of these results with Science Team members
(Hutchings, Tandon)
k. Non-Zero Gap Time
i. May need to adjust BOD.
ii. Image at 5 settings, 0.3, 0.6s, 0.9s, 1.2s, and 1.5s.
l. Stacking, Normalization
i. BOD operates on images as they are read, so will not need to adjust.
ii. Stacking with and without normalization, dark and illuminated frames.
Estimated Time: 1 day (including data reduction/analysis time)
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10. Flat Field: MCP Voltage Calibration – Nominal, Low Gain, Count Rate Linearity, Sub Window,
Fixed Pattern Noise
a. This voltage must be optimized before continuing beyond this task
i. PHD’s, FWHM’s, and Photometry significantly affected by these values
b. HV Tank ~10^-7 Torr, UV Arm ~10^-5 Torr
c. CPU oriented in line with light source
d. UV mono at 230nm
e. Iris positioned for count rate ~100-500 hundred/frame
f. Use safe BOD settings
i. Length = 3 pixels; Height = 6000 ADU; Frames = 3 frames
g. Turn OFF UV Source between voltage variation imaging runs
i. Always turn off when not in use so that photocathode is not overexposed
ii. Always begin imaging only after UV source is ignited to ensure BOD functionality
h. MCP Voltage, Count Rate, Windows, Fixed Pattern Noise
i. If reference photometer calibration to CPU hasn’t been adequately determined
yet, determine nominal HVU voltage CPU count rates vs. photometer count
rates to attain up to ~4000 counts/frame on CPU.
ii. Begin at low count rate (~50 counts/frame at nominal voltage), going to high
(~4000 counts/frame at nominal voltage): (~) 50, 500, 1500, and 4000 counts
per frame
iii. At each constant Count Rate:
1. Vary MCP voltage through a range of voltages, going from no events
detected (~1700V) to above nominal (2100V) in 100V steps (use
nominal voltage (2020V) at 4th step)
2. At each MCP Voltage
a. Image Full Frame size first, ensuring system doesn’t BOD at high
count rate/voltage
b. Image at 2 (1?) (fixed for all tests) sub window sizes (small and
mid range)
c. Image in Integration Mode and the 3 Centroiding Modes
d. Not all possible combinations of above settings will be tested
due to time constraints and DS safety/MCP depletion issues.
1 : Ex. No high count rate/high voltage combination
iv. Fixed pattern noise only at nominal voltage and 500c/s
1. At nominal voltage and 500c/s, image long enough to get at least 1000
counts per axial centroiding element (1/32 pixel).
a. Approximately 20 minutes for 512*32*1000 = 16 million counts
at 500 counts/frame at 29Hz. May image longer if higher SN
desired.
b. Integration and 3 Centroid modes.
Estimated Time: ~days to one week - TBD during Calibration Task Sheet development.
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11. Flat Field: Wavelength Characterization
a. Must have determined/confirmed optimal operating voltages before commencing
b. Count rate ~500/frame at each wavelength
c. HV Tank ~10^-7 Torr, UV Arm ~10^-5 Torr
d. CPU oriented in line with light source
e. UV mono at 230nm
f. Turn OFF UV Source between imaging runs
i. Always turn off when not in use so that photocathode is not overexposed
g. Use BOD settings as above
i. Length = 3 pixels; Height = 6000 ADU; Frames = 3 frames
h. Wavelength Characterization
i. Only 2 extra wavelengths, low-range and high-range for this detector: 190nm
and 270nm (230nm done above)
ii. At nominal voltages only
iii. Integration Mode and 3 Centroiding Modes
iv. Image for ~20 minutes each mode, to build suitable histograms and SN per axial
centroiding element (1/32 pixels)
1. May image longer if higher SN desired.
Estimated Time: 8 hours
This is the end of flat field optics HV imaging.
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Preliminary Laboratory Tasks:
12. HV System Cycle: Insert Spot-Focusing Optics
a. Entire GSE System Shut Off
b. UV Arm gate valve closed to remain at high vacuum
c. Main Chamber relieved to atmosphere
i. Use clean N2 purge to near atmosphere to keep particle count low inside
chamber.
d. Main Chamber lid removed
i. Immediately secure CPU dust cover to protect CPU window
e. Replace Flat Field Optics with Focused Multi-Spot Mask Optics
i. Use the 25um hole grid mask.(?)
ii. Also have 75um and alternating 25um, 50um, 75um mask
1. Alternating mask would give range factor ~10 in count rate
f. Remove CPU dust cover
g. Secure main chamber lid
h. Begin Main Chamber HV pump down
i. 24-48 hours for nominal (empty, clean tank) pump down to ~10^-7 Torr
Can use pump down time for data analysis.
Spot mask drawing at end of this document.
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13. Point Source Mask: Optical System Characterization
a. Direct Illumination, HVU ON
b. HV Tank ~10^-7 Torr, UV Arm ~10^-5 Torr
c. Use safe BOD settings
i. Length = 3 pixels; Height = 6000 ADU; Frames = 3 frames
d. CPU oriented in line with light source, beginning near theoretical focus position
i. Use pre-saved manipulator position setting
ii. Watch manipulator move into position
1. Clearance safety previously checked with dummy components
e. UV Mono at 230nm
f. Characterize point source count rates
i. Point Source count rates should be <~5 frames/count at a spot position
ii. Record UV iris position and reference photometer count rates
iii. Vary iris position and determine spot count rate vs. reference photometer
g. Characterize optimal focus position/manipulator alignment
i. Will require multiple imaging runs at different manipulator positions
ii. Will require sufficient integration time to get spots of high enough SN for focus
position analysis
iii. CPU imaging plane not guaranteed to be parallel to focus plane
1. CPU Manipulator may need to be rotated (only longitudinal rotation
possible)
iv. Focus position will be sensitive to wavelength
Estimated Time: 8 Hours
27
Detector Calibration Tasks:
14. Point Source Mask: MCP Voltage Calibration – Nominal, Low Gain, Count Rate Linearity, Sub
Windows
a. Can also use this data for geometric distortion; if require more areal coverage, do
Supplemental Task.
b. HV Tank ~10^-7 Torr, UV Arm ~10^-5 Torr
c. UV mono at 230nm
d. CPU Manipulator in focus position determined in Task 13.
i. This not necessary as collimated beam through pinholes gives small spots.
e. After mask is focused, require only enough data to get high SN (10-20?) in spot areas
f. Iris at various positions
i. Count rates from ~20 frames/count (~0.05 counts/frame) to ~0.5 frame/count
(~2 counts/frame) at a spot position
g. Use safe BOD settings
i. Length = 3 pixels; Height = 6000 ADU; Frames = 3 frames (lower for spot?))
h. Turn OFF UV Source between voltage variation imaging runs
i. Always turn off when not in use so that photocathode is not overexposed
ii. Always begin imaging only after UV source is ignited to ensure BOD functionality
i. MCP Voltage, Count Rate, Windows, Geometric Distortion
i. If reference photometer calibration to CPU hasn’t been determined yet,
determine nominal HVU voltage CPU count rates vs. photometer count rates to
attain up to ~2 counts/frame/spot on CPU (i.e., extrapolate from lower rates).
ii. Begin at low count rate (~20 frames/count at nominal voltage), going to high
(~0.5 frames/count at nominal voltage): (~) 20, 10, 5, and 0.5 frames/count
iii. At each constant Count Rate:
1. Vary MCP voltage through a range of voltages, going from no events
detected (~1700V) to above nominal (2100V) in 100V steps (use
nominal voltage (2020V) at 4th step)
2. At each MCP Voltage
a. Image Full Frame size first, ensuring system doesn’t BOD at high
count rate/voltage
b. Image at 2 (fixed for all tests) sub window sizes (small and mid
range)
c. Image in Integration Mode and the 3 Centroiding Modes
d. Not all possible combinations of above settings will be tested
due to time constraints and DS safety/MCP depletion issues.
1 : Ex. No high count rate/high voltage combination
iv. Geometric Distortion:
1. At nominal voltage and 5 frames/count, image longest to get good SN
for geometric distortion characterization
Estimated Time: ~days to one week - TBD
28
15. Point Source Mask: Supplementary Geometric Distortion Characterization
a. This task required only if more areal coverage is required than that attained in the
previous task.
b. UV Mono at 230nm.
c. HV Tank ~10^-7 Torr, UV Arm ~10^-5 Torr
d. Move manipulator into appropriate position, re-determine/confirm focus, integrate
i. X and Y translations of the manipulator should be mostly independent of (i.e.
parallel to) the focus plane for UV Arm
e. Geometric Distortion:
i. At nominal voltage and 5 frames/count, image longest to get good SN for
geometric distortion characterization
Estimated Time: ~day to week - TBD as required
29
16. Point Source Mask: Large Spot – Count Rate Linearity Characterization
a. HV Tank ~10^-7 Torr, UV Arm ~10^-5 Torr
b. UV mono at 230nm
c. CPU Manipulator moved away from optimal focus to produce large spot
d. Use nominal HVU voltages only
e. Iris at various positions
i. Count rates from ~20 frames/count (~0.05 counts/frame) to ~0.5 frame/count
(~2 counts/frame) at a spot position: ~20, 10, 5, 0.5 frames/count.
1. Adequate SN for centroid histograms
Estimated Time: ~1 Day
30
17. Point Source Mask: Moving Spot
a. Number of rates and time spent on this task dependant on time left in schedule
b. HV Tank ~10^-7 Torr, UV Arm ~10^-5 Torr
c. UV mono at 230nm
d. Manipulator movement and clearances MUST BE ensured safe for this procedure.
i. Do NOT turn ON y-axis (distance between detector face and optics)
microcontroller.
ii. Only move in lateral directions to detector face (x and y)
e. Slew manipulator at rate similar to spacecraft drift
i. 7um/s (on detector face) typical rate
ii. 75um/s on (detector face) maximum rate (i.e., 1 Star250 pixel/s – [25um/s])
iii. All 3 centroid algorithms
iv. Post analysis: Explore shift and add of centroids, dynamically and with known
slew rate
Estimated Time: ~1day
31
Summary Table
Loosely estimated with ~8 hour working days; can use night’s and weekend for extended
calibration time.
Day
1
2
2
3-4
5
5
5
6
7
7
8-13
14
15-16
17
Task #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Description
Unpack and Install
System Start, HVU Off
System Start, HVU On
Pump Down
System Start, HVU Off
System Start, HVU On
UV Source Characterization
Dark Frame Characterization
Flat: BOD
Flat: Reset Bias & Gain
Flat: MCP, Linearity, Noise, etc
Flat: Wavelengths
HV System Cycle: Spot Optics
UV Source Characterization
Point Source: MCP, Linearity,
Distortion, etc
Point Source: Supplementary
Distortion
Hours
8
3
3
24-48
1
1
6
8
2
6
40
8
24-48
8
18-23
15
24-26
16
27
17
Point Source: Large Spot
24
28
18
Point Source: Moving Spot
24
32
40
24
33