WFPC2 SMOV3B
CLOSURE REVIEW
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
1
REVIEW OF WFPC2
VERIFICATION REQUIREMENTS
DURING SMOV3B
Anton Koekemoer
(WFPC2 Group, STScI)
With the collaboration of:
Shireen Gonzaga, Inge Heyer, Lori Lubin,
Vera Kozhurina-Platais, and Brad Whitmore
WFPC2 SMOV3B Goals
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
2
• Contamination Mitigation
–
–
–
–
Minimize UV flux for 12 days in Bright Earth Avoidance (BEA)
Protect Safe mode (shutter closed, F785LP in place, TECs off)
Cool down to –88o C only after the end of BEA
Frequent UV observations and weekly Decons after cooldown
• Instrument Health and Safety Verification
– Complete set of internal observations:
• biases, darks, Intflats, Visflats, UV flats, K-spots
– Repeated regularly throughout SMOV3B
• Calibration Verification
– Photometric filter sweeps, Earthflats, PSF verification, focus check
WFPC2 SMOV3B
Activities
Activity
ID
Description of
Activity
WFPC2-01
Transition from Protect Safe to
Hold, and to Protect Decon
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
3
Applicable
Time External
Requirements (hours) Orbits
J.10.4.1.1.1
20
Cool Down to –88o C,
WFPC2-03
UV Contamination Monitor
J.10.4.1.1.2
J.10.4.1.1.3
26
17
WFPC2-04 Lyman α Check
J.10.4.1.2.2
24
4
WFPC2-05 Flat Field Calibration
J.10.4.1.2.3
WFPC2-06 Relative Photometry Calibration
J.10.4.1.2.2
WFPC2-07 PSF Verification
J.10.4.1.2.1
J.10.4.1.2.4
4
WFPC2-08 Internal Monitors
J.10.4.1.2.3
3
-
No External Parallels <30 days
J.10.4.1.2.5
1
10
Transition to Hold, and
to Protect Decon
Requirement Number:
SMOV Activity Number:
SMOV Proposal ID:
Requirement Status:
Execution Status:
Description:
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
4
J.10.4.1.1.1
WFPC2-01
8949
SATISFIED
NOMINAL
• Recover WFPC2 from Protect Safe to Hold mode.
• Perform engineering matrix verification.
• Initiate transition to Protect Decon: enable CCD heaters on, radiator heat
pipe heaters on, close shutter Blade A, place filter F785LP in optical path.
Results:
• Successfully verified nominal operation of WFPC2.
• Placed WFPC2 in Protect Decon with CCD temperatures at +22 C.
o
Cool Down to –88 C,
Contamination Check
Requirement Number:
SMOV Activity Number:
SMOV Proposal ID:
Requirement Status:
Execution Status:
Description:
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
5
J.10.4.1.1.2
WFPC2-03
8950
SATISFIED
NOMINAL
• Cool down CCD cameras to –88o C. Monitor UV contamination on CCD
windows with frequent photometry of the standard star GRW+70d5824 in
the F170W filter, at 0, 3, 6, 12, 18, 24, 36, 48 hours after cooldown.
• If projected decrease is safely within 30%, continue operations at –88o C.
• Fast analysis turn-around required (<12h); typically <3-6h in practice.
• Preliminary focus check using 3 observations within 48h after cooldown.
Results:
• Average contamination rate from 0.65% /day (PC) to 0.93% /day (WF3).
• Slightly higher than normal (~0.4-0.5% /day), to be expected due to new
hardware and other SM3B-related activities.
• Total decrease never exceeded 10%, well within the 30% limit.
• Preliminary focus measurements showed no strong off-nominal behaviour
Contamination Check:
0–7 Days after Cool Down
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
6
UV Contamination
Monitor During SMOV3B
Requirement Number:
SMOV Activity Number:
SMOV Proposal ID:
Requirement Status:
Execution Status:
Description:
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
7
J.10.4.1.1.3
WFPC2-03
8950
SATISFIED
NOMINAL
• Continue monitoring UV contamination with frequent observations of the
standard star GRW+70d5824 in the F170W filter, at 3, 4, 5 and 6 days
after cooldown to –88o C, and before and after each subsequent Decon
(7, 14, and 28 days after cooldown).
Results:
• Contamination rate remained steady at <1 % / day.
• Largest decrease was never more than 10% for WF3, ~5% for the other
cameras (all safely within the maximum limit of 30% decrease).
• After each Decon, throughput was successfully restored to nominal value.
• Contamination rates now the same as pre-SM3B (~0.4-0.5% / day).
Contamination Monitor
for 4 weeks of SMOV3B
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
8
WFPC2 PSF Verification
Requirement Number:
SMOV Activity Number:
SMOV Proposal ID:
Requirement Status:
Execution Status:
Description:
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
9
J.10.4.1.2.1, J10.4.1.2.4
WFPC2-07
8954
SATISFIED
NOMINAL
• Obtain exposures over a wide dynamic range of a bright star
(GRW+70d5824) to characterize the extended wings of the PSF.
• Observe a crowded stellar field (Omega Centauri) with sub-pixel dithers
to construct critically sampled PSFs across the WFPC2 field-of-view.
• Characterize the PSF properties with respect to pre-SM3B data.
Results:
• PSF properties across the field consistent with pre-SM3B data.
• NCS was already turned on, thus PSF did not need to be remeasured.
Lyman α Check
Requirement Number:
SMOV Activity Number:
SMOV Proposal ID:
Requirement Status:
Execution Status:
Description:
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
10
J.10.4.1.2.2
WFPC2-04
8951, 8943 (pre-SM3B)
SATISFIED
NOMINAL
• Aim to measure Far-UV contamination on the WFPC2 pick-off mirror.
• Observe the WFPC2 primary standard star GRW+70d5824 in the Far-UV
with filters F122M and F160BW by themselves, and crossed with F130LP.
• Use the crossed F130LP measurements to compensate for red-leak.
• Compare the measured throughput from the single and crossed filters,
and compare these in turn to the pre-SM3B measurements, with a
required accuracy of 5%.
Results:
• No significant decrease in Lyman-α throughput compared to pre-SM3B.
Photometric Verification
Requirement Number:
SMOV Activity Number:
SMOV Proposal ID:
Requirement Status:
Execution Status:
Description:
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
11
J.10.4.1.2.2
WFPC2-06
8953
SATISFIED
NOMINAL
• Observe the WFPC2 primary standard star GRW+70d5824 through a
wide range of filters: F160BW, F170W, F185W, F255W, F300W,
F336W, F439W, F555W, F675W, F814W in all four cameras.
• Data obtained within 2 days after a Decontamination (for UV filters)
Results:
• No significant changes from pre-SM3B values for:
• Visible filters (to <1%)
• UV filters (to within measurement errors of 2 – 5%)
• Thus, WFPC2 photometric throughput not affected by SM3B.
Photometric Comparison
Methodology:
• For each filter, the difference between the
post-SM3B and the mean pre-SM3B countrate was determined.
• This difference was then expressed in terms of
the standard deviation of all the pre-SM3B
measurements (which is different for each
filter).
• Each “point” in the histograms corresponds to
the measured difference for a given filter.
Measurements:
• For PC and WF chips combined, the
distribution is offset from the mean by
0.34 sigma.
• For PC alone, the offset is 1.31 sigma.
• For the WF chips, the offset is 0.02 sigma.
-> No significant photometric change
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
12
Flat Field Verification
Requirement Number:
SMOV Activity Number:
SMOV Proposal ID:
Requirement Status:
Execution Status:
Description:
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
13
J.10.4.1.2.3
WFPC2-05
8952
SATISFIED
NOMINAL
• Obtain external (Earth) flat fields for four narrow-band filters:
F375N, F502N, F656N, F935N (20 images each).
• Combine the flat fields in each filter to remove cosmic rays and streaks.
• Compare with pre-SM3B images to quantify stability.
Results:
• Systematic changes less than 0.3% over the central area (400x400 pixels).
• Very low-level (0.1-0.2%) large-scale gradients, attributable to previously
measured slow long-term vignetting changes in the cameras.
• r.m.s in flat field ratio ~0.4% (WF), 0.8% (PC), consistent with photon noise.
• No significant changes due to SM3B.
Flat Field Comparison
• Ratio of post- / pre-SM3B Earth
flats, taken in F502N.
• The greyscale covers +/- 2%.
• There are no large-scale
changes with an amplitude
above 0.1-0.2%, well below the
calibration accuracy of 1%.
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
14
Internal Monitoring
Requirement Number:
SMOV Activity Number:
SMOV Proposal ID:
Requirement Status:
Execution Status:
Description:
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
15
J.10.4.1.2.3
WFPC2-08
8950
SATISFIED
NOMINAL
• Obtain routine internal observations to monitor basic instrument health and
optical alignment (bias, darks, Intflats, Visflats, UV flats, K-spots).
Results:
• No significant changes in gain, bias level, read noise, or dark current.
• Small change (0.2-0.5%) in Intflat illumination patterns, consistent with
slight time-dependent variation of the Carley bulbs.
• No significant Visflat changes, apart from documented pre-SM3B changes.
• No differences in the UV flats.
• No significant shifts in K-spot locations, apart from slight trends associated
with documented long-term changes in the camera geometry.
Internals: Read Noise
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
16
External Pure Parallels
Requirement Number:
SMOV Activity Number:
SMOV Proposal ID:
Requirement Status:
Execution Status:
Description:
SMOV3B CLOSURE REVIEW
30 September 2002
WFPC2
Anton Koekemoer (STScI)
17
J.10.4.1.2.5
SATISFIED
-
• No external pure parallels shall be scheduled during the first 30 days after
cooldown, unless this is required for testing parallel capabilities.
Results:
• No pure parallels were scheduled until 30 days after cooldown.