TIPS-JIM Meeting
18 January 2007, 10am, Auditorium
1.
ACS WFC Flat-Field Changes
Ron Gilliland
2.
The JWST Mid-Infrared Instrument
Margaret Meixner
Design Review Status
3.
Data Analysis for the JWST/BSTA Test
Warren Hack
Next TIPS Meeting will be held on 15 February 2007.
ACS WFC Flat-Field Changes
•
Temperature change from -77 C to -81 C on July 4, 2006 leads to expected
changes for flat fields.
•
Are L-flat measures stable before δT, and is there a change after cooldown?
(Yes/yes)
•
Are pixel-to-pixel measures stable before δT, and is there a change after
cooldown? (No/yes, but small.)
This summarizes two recent ISRs:
WFC L-Flats Post Cooldown 2006-06 (Gilliland, Bohlin and Mack).
Pixel-to-Pixel Flat Field Changes on the WFC 2007-01 (Gilliland and Bohlin).
Data available and processing approach.
•
Internal tungsten lamp exposures in F435W, F625W and F814W have been
routinely acquired to provide flat field tracking. Twenty epochs available pre- and
three epochs post-cooldown.
•
Standard set: 3 exposures to 50,000 e- each in each of three filters providing
Poisson limit near 0.0026 for co-added precision.
•
Pipeline .flt files have bias and dark subtraction, local processing to remove
cosmic rays.
•
•
•
A mean flat field over time, separately for pre- and post-cooldown is formed.
The ratio of post- to pre-cooldown means is formed.
A spatial median filter 65x65 pixels, stepped by 16 pixels to form 256x256 L-flats
is formed for each filter.
Ratio of Pre- to Post-cooldown, compared to stability.
L-flat changes across cooldown. 0.995 to 1.005
range, white corresponds to sensitivity loss.
Schematic used to define comparison areas.
Filter
Pattern
change
F435W
-0.61%
F625W
-0.38%
F814W
-0.15%
Same as at left, but rms over all pre-cooldown
epochs. Changes across δT are much larger
than inherent epoch-to-epoch changes.
Delivery of new L-flats.
•
We have updates directly available for F435W, F625W, and F814W -interpolation used for other filters in this range.
•
These “δ-L-flats” at each filter are applied as multiplicative corrections to all
existing pipeline LP-flats.
•
The 47 Tuc monitoring program data were used to show that stellar photometry
from two epochs close to, and pre-/post-cooldown showed relative changes
similar to those derived from the internals.
•
A full set of such corrected flats was made available in early November with useafter date of July 4, 2006. See ISR 2006-06 for further details.
•
Accuracies of these newly delivered post-cooldown flats are limited by errors
following from the original laboratory flats and pre-cooldown L-flat adjustments,
rather than limitations in these differential corrections.
Pixel-to-pixel Flat Field Changes
•
Can we simply do the same thing as before? That is create separate pre- and
post-cooldown internal flats, suppress L-flat changes and ratio the two to derive
pixel-to-pixel flat changes as a result of the δT?
•
A hint a why this doesn’t work appeared in Bohlin and Mack, The Internal ACS
Flat Fields, ISR 2005-09 which obviously discussed only pre-cooldown data: “The
only ubiquitous change observed in these flat fields is an excess of pixel
responses that are low.” “Replacing the pre-launch baseline with one of the flight
flats does not change the essential features”
•
The first task is to look further into the stability of flat fields at the individual
pixel response level, and then assess whether this allows a reasonable path to
providing updated flats, or the need for such.
Pixel-to-pixel response changes in time.
•
Started with 18 epochs of F435W internals precooldown and 6 epochs post-cooldown.
•
Removed the effect of changing L-flats by dividing
out spatial median filtered image.
•
•
Formed median over all pre-cooldown epochs.
•
Figure at right shows number of pixels at <-4%
per epoch. Values have been scaled up by 32/
Number of days since anneal to project to
number expected at end of anneal cycles. The ‘x’
are prior to WFC cooldown, the ‘o’ are after.
•
Linear correlation coeff over 14 points postSMOV, pre-cooldown is r = 0.926 allowing only
about a part per million chance of resulting from
uncorrelated data.
Tabulated how many pixels deviated by more than
1, 2 and 4% both + and - from the global median
in time.
Pixel-to-pixel deviations correlated with time since anneal.
•
Figure again shows the number of pixels at <-4%
deviant response in each epoch of internal flat data.
•
Linear trend shown in previous figure: --time since
launch-- has been divided out with normalization to
value at 2006.5 adopted.
•
This shows that the number of low response pixels
grows smoothly within anneal cycles, and then resets
with the vast majority of such pixels no longer
deviant at this level.
•
r = 0.958, chance of not being a real correlation is
less than one in ten million.
The number of pixels that are low by 4% in
any epoch is highly correlated with both
time since an anneal, and with overall time
that the WFC has been on-orbit.
More details on low response pixels.
•
•
•
Number at -2% is > X10 the number at -4%.
•
Number at positive deviations negligible compared to negative.
Number at -1% (still 3.8 σ) is X5 that at -2%, maybe doesn’t anneal as well.
The low response pixels are generally isolated, single pixels, are unique sets each
epoch (not a set that ‘telegraph’ back and forth) and are not correlated in space
with hot pixels, traps or other known pixel detects.
Wavelength dependence of low response pixels.
•
•
Plot for a random pre-cooldown epoch.
•
Points within 1% of (1,1) are not plotted,
only one of every 25 out to 2.5% of (1,1)
is shown.
•
All epochs checked show similar -- pixels
that show deviations are about twice as
low in F435W as F814W (and F625W is
half way in between).
Individual pixel values in normalized (to
median over all pre-cooldown epochs)
F435W internal flat plotted against the
same for F814W.
Low response effect is multiplicative, not additive.
•
At a few of the epochs a short exposure in F660N was substituted for one of the F814W exposures.
This provides internal flats with mean exposure level of 170 electrons, instead of standard 50,000.
•
We select all pixels showing <-4% deviation in one epoch and form a stack over all such pixels in both
F435W and F660N, normalize in each epoch by the local mean and evaluate medians within +/- 2 pixels
over this stack. A pure multiplicative effect should show the same depths, modulo wavelength
dependence. An additive effect would be much larger in the shallow exposure.
•
The result at F660N, compared to F435W used to flag the source pixels, is fully explained by
wavelength dependence. The effect is multiplicative, which seems to rule out temporary charge traps as
the cause.
•
Central pixels are surrounded by suppressed values consistent with charge diffusion.
F435W -- deep exposure -- 50000 e-
F660N -- shallow exposure -- 170 e-
1.000
1.000
0.999
1.000
1.000
1.001
1.000
0.999
1.002
0.999
1.000
0.997
0.991
0.997
1.000
0.998
0.997
0.992
0.997
0.998
0.999
0.992
0.954
0.992
0.999
0.999
0.994
0.966
0.992
1.000
1.000
0.997
0.991
0.997
1.000
0.999
0.996
0.992
0.997
0.999
1.000
1.000
0.999
1.000
1.000
1.000
0.999
1.000
1.003
1.001
Recovery of Low Response Pixels
•
Mean values by epoch for the set of
pixels at <-4% in 9th overall epoch.
•
Values are stable before epoch of
anomaly and recover to an
asymptotic level ~90% of the way
back to nominal.
•
Similar recoveries follow for -2% and
-1% deviation cases.
Absolute Quality of Pixel-to-Pixel Flats
•
The monthly growth of low response pixels is sufficient to add ~0.3% noise to the flat fields -comparable to intrinsic precision.
•
With anneals it will be 15 years before the current growth rate of low response pixels increases
enough to double the noise to 0.6%.
•
•
Without anneals the noise would double in only 120 days from the low response pixels.
•
A comparison of post-cooldown flats to pre-cooldown medians shows a number of deviant pixels
at each threshold that is still smaller than the monthly growth number, but not by a large margin.
One measure of current quality comes through estimating errors on stellar photometry: 2.6% of
stars would now show errors of 0.34%,
0.02% of stars with errors > 1.2% in F435W. In
F814W errors only half of this.
•
We’ve concluded that a flat field update is not currently needed (data doesn’t exist to support
except for F435W), but that we should restore the cadence of internal monitors to 6 times per
year to improve tracking and allow updates if such seem desirable in a year.
A comparison of the pre-cooldown median flat to the reference flat shows that the number of
deviant pixels is small compared to the number developing within each anneal cycle: our
reference flats are excellent.
TIPS-JIM Meeting
18 January 2007, 10am, Auditorium
1.
ACS WFC Flat-Field Changes
Ron Gilliland
2.
The JWST Mid-Infrared Instrument
Margaret Meixner
Design Review Status
3.
Data Analysis for the JWST/BSTA Test
Warren Hack
Next TIPS Meeting will be held on 15 February 2007.
Mid InfraRed
Instrument
Optical System
Critical Design Review (CDR)
TIPS Presentation:
Margaret Meixner
07-
MIRI Optical System CDR, 6th & 7th December 2006
MIRI CDR Process
l
Hybrid ESA/NASA CDR:
- Oral presentations for panel Dec 6&7 (NASA style)
- Main focus is on month long review of MIRI data packet by expert panels who
write and collect RIDs
- Anyone can submit a RID for MIRI (yes that means you) by giving it to one of
the panel or board members; Peter Stockman is on the board.
l
RIDs collected and sorted in January.
Disposition of RIDS presented to the board in February
This presentation provides a status of MIRI at the time of CDR.
l
l
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
Imager - Optical Requirements (Wright)
Requirements:
l > 2 square arcmin field of
view, with a 0.11 arcsecond
pixel scale
Image Quality
- > 58% of light within first
dark ring of model
telescope PSF
- Strehl ratio > 85 %
longward of 5.6 µm
l
Coronagraphy in 4 filter
bands (see Design Doc. for
details)
l
R=100 Spectroscopy
07-
1.7 arcmin
Simulated
MIRI Optical System CDR, 6th & 7th December
2006 NIR JWST field (Myungshin Im 1998)
This document contains proprietary information as stated on the cover page
1.3 arcmin
l
Design:
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
Medium Resolution Spectrometer - Format (Wright)
REQUIREMENT - Integral Field Spectroscopy with > 3 arcsec field of view from 5 to 28.5 µm.
10 arcseconds
Each channel’s field of view is sliced,
dispersed and detected.
Channel 1
(4.9 - 7.7 µm)
Channel 2
(7.4 - 11.8 µm)
Channel 3
(11.4 - 18.2 µm)
Channel 4
(17.5 - 28.8 µm)
Wavelength/Velocity
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
The MRS concept (Wells)
Collimator
IFU 1B
SW dichroic
Grating
Collimator
Grating
Collimator
Grating
Camera 1
FPA 1
Camera 2
FPA 2
IFU 1A
centre
dichroic
IFU 2A
IFU 2B
LW dichroic
Collimator
07-
Grating
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
MIRI MRS - Spectral Coverage (Glasse)
The MRS covers the 5 to 28 micron range in 12 sub-spectra
Spectral Resolving Power
l
How the spectra will
appear on the MRS’s two
detectors
07-
FRD
2.5.1.2
Wavelength [µm]
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
MIRI MRS
Target Acquisition required for some cases
Selection of:
•Grating wheel position: 1 of 3 sub-bands
•Detector readout
•Exposure time
•Dithering/Mapping
FOV Name
FOV (″×″)
sub-band name λ−range
λ-range (microns)
IFU1A
(microns)
3.7 × 3.7
4.86−7.74
Short
4.87−5.82
Medium
5.62−6.73
Long
IFU1B
4.5 × 4.7
7.43−11.84
IFU2A
6.1 × 6.2
11.44−18.20
IFU2B
17.53−28.75
07-
7.7 × 7.7
Short
6.49−7.76
7.45−8.90
Medium
8.61−10.28
Long
9.94−11.87
Short
11.47−13.67
Medium
13.25−15.80
Long
15.30−18.24
Short
17.54−21.10
Medium
20.44−24.72
Long
23.84−28.82
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
MIRI Optical
System Modes
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
07-
MIRI Optical System CDR, 6th & 7th December 2006
This document contains proprietary information as stated on the cover page
TIPS-JIM Meeting
18 January 2007, 10am, Auditorium
1.
ACS WFC Flat-Field Changes
Ron Gilliland
2.
The JWST Mid-Infrared Instrument
Margaret Meixner
Design Review Status
3.
Data Analysis for the JWST/BSTA Test
Warren Hack
Next TIPS Meeting will be held on 15 February 2007.
Data Analysis for the
JWST/BSTA test
Warren Hack, Perry Greenfield, Babak Saif
TIPS Meeting
18 January 2007
18-Jan-2007
Warren Hack (SAA/ESS)
BSTA ESPI Metrology Team
STSCI:
Swales Aerospace:
NASA/GSFC:
Babak Saif
Bente Eegholm
Peter Blake
Perry Greenfield
Marcel Bluth
Ritva Keski-Kuha
Warren Hack
Ivo Busko
18-Jan-2007
Warren Hack (SAA/ESS)
47
TIPS-JIM Meeting
18 January 2007, 10am, Auditorium
1.
ACS WFC Flat-Field Changes
Ron Gilliland
2.
The JWST Mid-Infrared Instrument
Margaret Meixner
Design Review Status
3.
Data Analysis for the JWST/BSTA Test
Warren Hack
Next TIPS Meeting will be held on 15 February 2007.