TIPS-JIM Meeting
21 October 2004, 10am, Auditorium
1.
JWST Science Instrument Target
Ed Nelan
Acquisitions, Concepts and Requirements
2.
Electronic Cross-Talk in the ACS/WFC
CCD Detectors
Mauro Giavalisco
3.
JWST Mid-Infrared Instrument (MIRI)
Calibration Planning
James Rhoads
4.
Summary of WFC3 Thermal Vacuum Test John MacKenty
Next TIPS Meeting will be held on 18 November 2004.
JWST Target Acquisition
TIPS
21-Oct-2004
Ed Nelan
Oct 21, 2004 TIPS
1
JWST SI Target Acquisition
lots of tiny apertures
Oct 21, 2004 TIPS
2
JWST SI Target Acquisition
demanding accuracy
JWST has observing modes that require target to be placed
in SI aperture with accuracy as demanding as ~10 mas.
MIRI IFU
90 mas
30 mas
12 mas
4 - 10 mas
MIRI LRS
NIRSpec
Coronagraphy
Oct 21, 2004 TIPS
3
JWST SI Target Acquisition
Position of target relative to guide star is not known
to better than 0.3”
• GSC-2, target coordinate errors
x
0.6”
Oct 21, 2004 TIPS
4
JWST SI Target Acquisition
demanding accuracy
Position of target relative to guide star is not known
to better than 0.3”
• GSC-2, target coordinate errors
x
0.6”
FGS to SI alignment error ~ 100 mas
Oct 21, 2004 TIPS
5
JWST SI Target Acquisition
demanding accuracy
Position of target relative to guide star is not known
to better than 0.3”
• GSC-2, target coordinate errors
x
0.6”
FGS to SI alignment error ~ 100 mas
Spacecraft roll error of 7” (1-σ)
~20 mas for 10’
GS-target sep
Oct 21, 2004 TIPS
6
Small Slew Accuracy
Oct 21, 2004 TIPS
7
SITAWG Status
Target acquisition concepts for each science
instrument have been baselined.
SI TAWG will propose target acquisition concepts
and recommend requirements to be allocated to the
flight and ground systems.
Report will be submitted to the STScI Mission Office
for project wide distribution.
Oct 21, 2004 TIPS
8
MIRI
A
B
C
D
4 coronagraphs
~26”
LRS
(0.6” x 5.5”)
IFU
Imager
~30”
Oct 21, 2004 TIPS
9
MIRI IFU Target Acquisition
Imager
“slicers” 180 mas width (min):
target to be placed within a slice
to an accuracy of 90 mas
Oct 21, 2004 TIPS
10
MIRI IFU Target Acquisition
1. Place target in subarray in Imager, image field,
determine “precise centroid” of target in subarray
Subarray with
well calibrated
alignment w.r.t.
Imager
IFU
IFU
~30”
reference field objects
Oct 21, 2004 TIPS
11
MIRI IFU Target Acquisition
2. Slew to place target in IFU. Imager records location
of ref stars: allows map of IFU spectra to target’s structure
Imager
IFU
~30”
reference field objects
Oct 21, 2004 TIPS
12
MIRI IFU Target Acquisition
• target “centroiding” algorithm must be robust to extended objects
• many IFU targets will not be point sources,i.e., have structure
• target acquisition image + location of reference stars in Imager
FOV maps IFU spectra to target’s structure
Imager
TA subarray
IFU slices lack spatial information
Oct 21, 2004 TIPS
13
Coronographic Target Acquisition
Coronagraphic targets can be very bright (JAB < ~4 for a G
star at 10 pc). Need to use
•
•
TA procedure needs to avoid inducing “persistence”
•
Sub arrays
Attenuators
exposing pixels near the coronagraph to the bright star as it is
placed behind the mask/spot reduces contrast, leads to loss of
sensitivity to detect putative planet.
Targets “acquired” (~10”) away from the coronagraph.
•
slew from acquisition location to mask must be small amplitude
possible for best accuracy.
Oct 21, 2004 TIPS
14
NIRCam Target Locate
Slew target to neutral density region
Center target on sweet spot of ND region
• Centroid
• Move to center of sweet spot
• Iterate as necessary
Center target on coronagraphic mask
• Rotate pupil wheel (no sky on SCA)
• Move target to coronagraphic mask
• Set pupil wheel to coronagraphic pupil
• Options to improve centering:
– Peakdown = minimum flux
– Quadcell = make flux distribution symmetric
– Centroid other stars elsewhere on SCA
10 arcsec
(Courtsey of Peter McCollough)
Oct 21, 2004 TIPS
15
NIRCam Target Locate
Slew target to neutral density region
Center target on sweet spot of ND region
• Centroid
• Move to center of sweet spot
• Iterate as necessary
Center target on coronagraphic mask
• Rotate pupil wheel (no sky on SCA)
• Move target to coronagraphic mask
• Set pupil wheel to coronagraphic pupil
• Options to improve centering:
– Peakdown = minimum flux
– Quadcell = make flux distribution symmetric
– Centroid other stars elsewhere on SCA
10 arcsec
(Courtsey of Peter McCollough)
Oct 21, 2004 TIPS
16
NIRCam Target Locate
Slew target to neutral density region
Center target on sweet spot of ND region
• Centroid
• Move to center of sweet spot
• Iterate as necessary
Center target on coronagraphic mask
• Rotate pupil wheel (no sky on SCA)
• Move target to coronagraphic mask
• Set pupil wheel to coronagraphic pupil
• Options to improve centering:
– Peakdown = minimum flux
– Quadcell = make flux distribution symmetric
– Centroid other stars elsewhere on SCA
10 arcsec
(Courtsey of Peter McCollough)
Oct 21, 2004 TIPS
17
Small Slew Accuracy
Use the largest GS -> coronagraph lever arm to estimate roll induced
error of placing target at coronagraph.
• For NIRCam & FGS-TF this is ~10 arcmin
10” slew from NIRCam’s ND spot to coronagraph is accurate to ~9 mas
(NGST estimate).
Might be ok NIRCam & FGS-TF coronagraphy requirements
Oct 21, 2004 TIPS
18
Small Slew Accuracy
MIRI needs ~ 4 to 5 mas accuracy for 4 quadrant phase mask (4QPM)
coronagraphs.
MIRI has the longest FGS-SI lever arm (16 arcmin).
Pointing error after a 10” slew, due mainly to roll error, ~15 mas (NGST
allocated 20 mas error).
Oct 21, 2004 TIPS
19
MIRI Coronagraphy Target
Acquisition
A
B
C
4QPM is transparent to wide bandpass neutral density attenuator
Locate star in subarray (A)
Slew to place star at coronagraph (B)
Center star at coronagraph using ND attenuator (C)
Final slew will be small (<0.2”), accurate to ~ 5 mas.
Oct 21, 2004 TIPS
20
NIRSpec
Oct 21, 2004 TIPS
21
NIRSpec
Target acquisition goal is to be able to observe an arbitrary
distribution of ~100 objects across the NIRSpec FOV in two
pointings with pre-selected MSA settings.
• Due to slit transmission curve, targets must be within the central 1/2
of the MSA (in spectral dimension) to meet requirements related to
photometric accuracy.
• Slope of slit transmission curve on exit from plateau requires targets
to be placed relative to MSA with ~12 mas (1-s) accuracy in spectral
direction.
Oct 21, 2004 TIPS
22
100 _m
20 _m
Magnetic Stripes on MSA Frontside
MSA Light Shields
100 _m
Oct 21, 2004 TIPS
MSA Backside
23
NIRSpec Target Acquisition
A
B
C
D
Oct 21, 2004 TIPS
24
NIRSpec Target Acquisition
dispersed spectra
closed shutters
Approximately 50% of targets can be placed simultaneously near peak of
transmission curve (yellow and blue). The others (red) can not and must be
observed with a different pointing.
Oct 21, 2004 TIPS
25
NIRSpec Target Acquisition
dispersed spectra
NIRSpec TA requirements allow for targets of interest in the FOV to be
observed with two pointings. If these are not meet, additional pointings would be
required. Note, yellow and blue stars can not be observed simultaneously if their
spectra would overlap onto common pixels.
Oct 21, 2004 TIPS
26
NIRSpec Target Acquisition
Observed location of NIRSpec TA reference stars.
Oct 21, 2004 TIPS
27
NIRSpec Target Acquisition
TA slew vector
Desired location of NIRSpec TA reference stars. Expect the TA slew
amplitude ~GSC-2 astrometric error (about 0.3”)
Oct 21, 2004 TIPS
28
NIRSpec Target Acquisition
NIRSpec Reference stars for Target Acquisition properly placed at
“science attitude”.
Oct 21, 2004 TIPS
29
NIRSpec Target Acquisition
dispersed spectra
closed shutters
Oct 21, 2004 TIPS
30
NIRSpec Target Acquisition
Estimate of errors contributing to NIRSpec target
acquisition suggests 12 mas accuracy is not met.
Most significant source of errors is internal to
NIRSpec, for example:
• MSA to detector alignment
• Imaging mirror non-repeatability
• NIRSpec imaging capability (for ref star centroids)
Consequence
• need 3 pointings to acquire all science data
• or not get spectra of all targets.
Oct 21, 2004 TIPS
31
Mauro Giavalisco
Cross-Talk in the ACS/WFC
CCDs
Oct-20
TIPS
Cross-Talk Facts
• Electronic cross-talk observed in WFC CCDs
• Consists of ghost images in adjacent quadrants in locations
mirror-symmetric to those of the sources
• Ghosts are very low-level depressions (~a few e-)
• SB (flux) of ghosts has weak, non-linear, noisy correlation
with SB (flux) of sources; XT different in different quads
• Ghost SB depends on the sky background (the higher the sky
the lower the cross talk)
• Ghosts are additive (as opposed to multiplicative) images:
no effect on photometry
• Use of GAIN=2 minimized the strength of the cross talk
• Very similar XT observed in the Lab in the WFC3 UVIS
CCDs
Oct-20
TIPS
References
• Giavalisco, M. 2004 ACS-04-13
• Giavalisco, M. 2004, ACS-04-12
• Baggett, S., et al. 2004, WFC3-04-11
Oct-20
TIPS
F850LP
2120 sec
(GOODS)
Oct-20
TIPS
GG
F606W
1060 sec
(GOODS)
Oct-20
TIPS
S2
F475W
1215 sec
(UGC1014)
Sky ~ 35 e-
Oct-20
S1
TIPS
F475W
1215 sec
(UGC1014)
Sky ~ 70 e-
Oct-20
TIPS
The cross-talk strength
as a function of the
sky background.
Each data point is the
average of three measures
from three different images
Oct-20
TIPS
The cross-talk dependence on the SB (flux) of the source
Oct-20
TIPS
The cross-talk dependence
on the flux of the source:
another representation.
The median and mode of the
distribution of victim pixel
values as a function of the
source pixel value.
Source image:
F850LP, 2120 sec
Sky ~12 e-/pix
Oct-20
TIPS
The cross-talk dependence
on the flux of the source:
another representation.
The median and mode of the
distribution of victim pixel
values as a function of the
source pixel value.
Source image:
F850LP, 2120 sec,
Sky ~18 e-/pix
Oct-20
TIPS
Effect on photometry
• If multiplicative (gain variation), magnitude
can be estimated from sky variation.
• If same source (bright star ideal) is observed
once within and once outside of XT patch,
gain variation can be tested.
• Gain variation ruled out at the15-σ level:
XT behaves as an additive effect.
Oct-20
TIPS
Effect on photometry
S1: 3 measures inside and 3 outside of XT patch
S2: all measures always outside of XT patch
Oct-20
TIPS
GG: 1 measure inside and 2 outside of XT patch
GAIN=1 vs. GAIN=2
Images taken with
same passband
and exposure time,
but different gain
GAIN=2
GAIN=1
Oct-20
TIPS
GAIN=1 vs. GAIN=2
GAIN=1
Oct-20
TIPS
GAIN=2
Conclusions
• XT mostly a cosmetic nuisance
• Low level (a few e- for most source fluxes)
• Additive component; nearly inconsequential for
photometry
• Noisy effect: correlation of XT value and source
flux has large scatter
• Advice is against introducing correction
• Use of GAIN=2 setting minimizes XT and has
no negative counter-effects on observations
Oct-20
TIPS
Calibration Plans for the Mid Infrared
Instrument (MIRI) on JWST
James Rhoads
for the
MIRI Calibration Working Group:
Meixner, Rhoads, Engelbracht, Rieke, Brandl,
Glasse, Lim, Hutchinson & Ressler
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
1
Scope and Context of Presentation
MIRI Calibration Planning is under way.
This is a “midstream” presentation to
• Summarize planning effort so far;
• Solicit expert input from the STScI community;
• Incorporate experience from other instruments in
MIRI calibration planning.
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
2
MIRI Calibration Context and Status
We are “midstream” in MIRI calibration planning.
Four documents outline plans:
• MIRI Calibration Requirements Document;
• MIRI Calibration Plan (Overview and routine onorbit calibrations)
• MIRI Performance Test Specification (Ground
testing)
• MIRI Commissioning Plan (On-orbit checkout)
So far, drafts exist for three of these, and two are
fairly mature.
The plans need to remain flexible at this early date.
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
3
Instrument Calibration
•
STScI will coordinate the development of an integrated
calibration plan by all the instruments
–
–
–
•
STScI benefits from HST experience
–
–
•
I&T = PI responsibility
Commissioning = PI responsibility
Post-commissioning = STScI responsibility
Calibrations planned using the integrated planning tool
Yearly cycles for calibration programs tied to TAC
Calibration data will come from 4 sources:
1)
2)
3)
4)
science data
observations done in parallel with science observations
observing time dedicated to calibration
ground testing calibration files
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
4
MIRI has four Science Modes
1. Photometric Imaging
3. Coronagraphy
2. Low Resolution Spectroscopy
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
5
MIRI has four Science Modes
4. Integral Field Unit Spectroscopy
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
6
MIRI Calibration Requirements Document:
FRD Requirement Number FRD Requirement
Test ID(s)
Rationale
MTS Requirements
On orbit checkout?
SODRM program ID
Yes
Monitor under SODRM
329
Yes
Monitor under SODRM
329
No
Monitor photometric
color terms under
SODRM 325
2.2 Photometric Imaging
2.2.1 General Characteristics
2.2.1.1 Field of view
The imager field of view shall have an area equivalent
IMG-OPT-01
2.2.1.2 Pixel scale
to at least 2.2 square arc minutes ´(6/D)2. The ratio of
long to short side of the field shall be no greater than
2
1 nominal pixel size shall correspond to _/2D of the
The
IMG-OPT-02
PSF at 7(TBR)µm
2.2.1.3 Spectral bands
MIRI shall provide imaging from 5 to 27mm in a total of
12 passbands. Approximately 6 of these passbands
shall be used for broad spectral energy distribution
determination, with the remainder reserved for
photometric identification of broad spectral featu
IMG-RAD-09
TIPS/JIM: MIRI Calibration Plans
The FOV scan will go beyond the MIRI
imager FOV edges, establishing FOV
size and instrument offset
MTS 513.02, MTS 522.01,
MTS 523.02, MTS 524.01,
MTS 524.02, MTS 524.05,
MTS 524.07
This test will establish the PSF size, the MTS 521.01, MTS 522.01,
pixel size will then be determined relative MTS 524.06
to this.
Dedicated spectral passband
MTS 541.01, MTS 542.02,
measurement
MTS 542.03
James Rhoads (STScI) - October 21, 2004
7
Calibration Philosophy Overview
• Consider a draft data reduction pipeline.
• Determine calibration files needed for pipeline.
• Decide how those files can be generated (in-orbit,
commissioning, ground test, analysis).
• Look for “missing links” (beyond pipeline).
• Some guiding principles:
– No end-to-end test (Telescope+MIRI) possible before flight
– Stand-alone ground testing of MIRI is planned
– (Almost) all ground-test results will be verified on-orbit with
celestial calibrators
– Some additional on-orbit tests will plug “gaps” in ground
testing, too.
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
8
MIRI Calibration Plan: MIRI Calibration Process: A
Data frame
from
Multi-Accum
SlowMode
ID bad pixels
Library
Dark Frames
Subtract
Reference
Pixels and
Dark frames
Bad Pixel Mask
Or Table
Reference Pixel Data:
Reference pixels for rows
Reference output
Corrected single
Frame
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
9
Focal Plane Array Calibrations
Some calibration needs are same for all three FPAs
in MIRI.
• Read noise (infer from short darks)
• Dark-bias frames
• Subarrays: Dedicated calibrations for subarrays
limit # supported.
• Latent image reduction through anneals
– Also helps with persistence due to CR hits.
– No associated calibration file.
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
10
MIRI Imager Calibration Process: B
Corrected
Individual
Frames from
One Integration
Local background
Frames or
Library Sky frames
Nonlinearity Correction;
Up-the-Ramp Fitting
with Cosmic Ray
Rejection and
Saturation Flagging
Nonlinearity
coefficient
maps
Background
Subtraction
Flat Field
frame
Populate the
Header w/
diagnostics
Absolute
Flux
Calibration
Flat fields:
Pixel flat
Low Freq. Flat
Absolute
Flux
Conversion
Factors
Flux calibrated
Data frame,
Uncertainty frame,
Mask
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
11
MIRI Imager Calibration Process: C
Flux calibrated
data frames at
a dither position
Drizzle dither
positions together
into one mosaic
Offset files
Source
extraction &
catalog
generation
Gap free final
image &
catalogs
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
12
MIRI Imager Calibration files
1. Bad pixel mask
2. Dark-bias frames
3. Short Dark frames (for Read noise and Bias
measurements)
4. Library sky frames
5. Internal flat fields for high frequency variations
6. Sky flats and/or points of light flats for low
frequency variations
7. Saturation counts map
8. Linearity counts map
9. Standard star measurements
10.Astrometric solutions file
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
13
MIRI coronagraphic calibration files
Coronagraphy: Add in
•
•
•
Target acquisition image of target with neutral density filter
Point spread function standard taken with the same corongraphic
setup up and close in time to the science observation.
Information on the location of the coronagraphic hole or center of
the phase mask
Low Res Spectrograph: Add in
1. Wavelength calibration file
2. Location of the slit information on the FPA
Integral Field Unit: Add in
1. Table of slice and wavelength positions on the FPAs
2. Wavelength calibration spectra
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
14
Internal Calibration Unit
• Internal calibration source has hot filaments
(~800K, tunable) + concentrator (oblate spheroid,
10mm size) + relay optics.
• Calibration light feeds into pupil planes of both
IFU and imager at the central obscuration, using
reflective optics.
• Redundant backup filament.
• In IFU, a third filament (lower intensity) will feed a
wavelength calibration system.
• “Cheap” to use, but light does not pass through
entire optical train.
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
15
Celestial calibrators
• Absolute flux calibration: use stars
~100 stars, may need Spitzer data for fainter MIRI appropriate
standards
- used for flux, linearity, color
-may need ground based (VISIR) spectroscopy to check stellar
atmosphere models of a few
- How do we choose stars w/o circumstellar dust? MIRI will
be sensitive to this?
• Spectral calibrators: use PN in Mag. Clouds
• Astrometric standards: same clusters as NIRCam?
•Use telescope pointing for IFU?
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
16
In-orbit Internal Calibration Modes
1.
2.
3.
4.
5.
Dark Current + Bias
Flat field calibration
Wavelength calibration for the IFU spectrograph
Wavelength Cal. For LRS?
Read Noise Calibration
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
17
In orbit Monitoring Programs
• 321 Flat Field Monitoring for MIRI Imager
• 323 Dark Monitoring for MIRI Integral Field Unit (IFU) Spectrometer
and Imager
• 325 Photometric Monitoring for MIRI Imager
• 329 Astrometric Monitoring for MIRI Imager
• 322 Flat Field Monitoring of the MIRI IFU
• 326 Spectrophotometric Monitoring of the MIRI IFU
• 324 Wavelength Calibration Monitoring for MIRI Integral Field Unit
(IFU) Spectrometer
• 327 Spectrophotometric Monitoring of the MIRI LRS
• 331 Wavelength Monitoring of the MIRI LRS
• 328 Coronagraph photometric monitoring
• 330 Coronagraph center location monitoring
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
18
MIRI Coronagraphic Calibration Process: C
Flux calibrated
Data frames
PSF subtraction
From individual
frames
Position of object
Behind hole
Coronagraphic
Image of PSF
standard
Target
Acquisition
Image and
Monitoring
Information
Co-addition of several
PSF-subtracted frames
at multiple roll angles
Final flux calibrated
High S/N
PSF subtracted
Coronagraphic
image
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
19
MIRI LRS Calibration Process: B
Corrected
Individual
Frames from
One Integration
Local or library
background
frames;
Flat fields
Nonlinearity Correction;
Up-the-Ramp Fitting
with Cosmic Ray
Rejection and
Saturation Flagging
Background subtract,
Flat field, and
Extract 2-D
LRS Spectrum
Populate the
Header w/
diagnostics
Nonlinearity
coefficient
maps
Absolute
Flux
Calibration
Wavelength
Calibration
Absolute
Flux
Conversion
Factors
Wavelength
Conversion
Factors
Flux calibrated
Data frame
Uncertainty frame
Mask
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
20
MIRI LRS Calibration Process: C
Flux & wavelength
calibrated
2-D spectrum at
a dither position
Drizzle dither
Positions together
Offset files
Extract 1-D
Spectrum of
Source
Gap free final
Spectrum
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
21
MIRI IFU Calibration Process: B
Corrected
Individual
Frames from
One Integration
Local or library
background
frames
Nonlinearity Correction;
Up-the-Ramp Fitting
with Cosmic Ray
Rejection and
Saturation Flagging
Background
subtraction
Populate the
Header w/
diagnostics
Nonlinearity
coefficient
maps
Wavelength
calibration &
Data cube
extraction
Mapping from
x, y, and mode
to
RA, Dec, _
Flat fielding
and
Absolute flux
calibration
Flat field frames
and
Absolute flux
conversion factors
Flux calibrated
Data frame
Uncertainty frame
Mask
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
22
MIRI IFU Calibration Process: C
Flux & wavelength
calibrated
data cube at
a dither position
Drizzle dither
Positions together
Offset files
Gap free final
data cube
Extract 1D or
2D spectra,
Line images,
Spectral index maps,
etc.
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
23
MIRI Calibration Plan
PROGRAM NO.: 321
AS-OF DATE: 8 JUNE 2004
PROGRAM TITLE:
FLAT FIELD MONITORING FOR MIRI IMAGER
SYNOPSIS: WE PROPOSE TO MONITOR THE FLAT FIELDING STABILITY
OF THE MIRI IMAGER. WE ARE CONCERNED BOTH BY LONG AND BY
SHORT TERM EFFECTS IN THE TELESCOPE OR THE IMAGER. EVERY
WEEK WE PLAN TO TAKE TWO INTERNAL FLATS IN EACH OF THE SIX
BROAD BAND FILTERS. THREE TIMES A YEAR, WE WILL OBTAIN SKY
FLATS IN SIX BROAD BAND FILTERS. TWICE A YEAR WE WILL OBTAIN
INTERNAL FLATS IN ALL FILTERS. ONCE A YEAR WE WILL OBTAIN
SKY FLATS IN ALL THE FILTERS, THE CORONAGRAPH FILTERS AND
THE LOW RESOLUTION SPECTROGRAPH (LRS) PRISM.
SAMPLE AND SKY COVERAGE:
TWO LOCATIONS IN THE ZODICAL LIGHT: ONE HIGH BACKGROUND
AND ONE LOW BACKGROUND.
WE MAY WANT TO CONSIDER CHOOSING TWO SPECIFIC SPOTS IN THE
ZODIACAL BELT THAT ARE “IDEAL” FOR SUCH MEASUREMENTS. IF
THE SAME ARE USED THESE COULD DOUBLE AS THROUGHPUT
MEASUREMENTS.
Basis for exposure time estimates (needed S/N and brightnesses):
S/N ~1000
Sky flats: depends on zodiacal light background
Internal flats: ~10^14 photons/second => short 10 second exposures
INSTRUMENTS AND OBSERVING CONFIGURATIONS:
DETECTOR READOUT: FASTMODE AND SLOWMODE
SKY FLATS 3 TIMES A YEARS:
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
24
MIRI Performance Test Specification
easure the PSF, to verify that the pixel size corresponds to ë/2D of the PSF at To measure the an
1. IMAGER TESTS
1.1 OPTICAL PERFORMANCE TESTS
1.1.1 IMG-OPT-01 FOV Measurement
Goal: To measure the imager FOV and to detect ghosts.
Outline: A point source is scanned across the entire imager array, nominally in a raster pattern.
This could either be done via discrete steps (several pixels) or via a continuous scan. As long as
a sufficient row length and number of columns are chosen, the edge of the FOV will be found, i.e.
this will need a larger area than the FOV as the instrument may move in cool down. As the whole
FOV is being scanned, at various positions ghosts may be detected. The positions of these will
be noted and IMG-OPT-02 will be used for follow up measurements.
Equipment Needed: A point source imaged on to the imager FOV via a telescope simulator, this
will need to have a FOV scanning capability which goes beyond the nominal edge of the FOV.
Number of Pixels/Positions: This should be done at all relevant filter wheel positions.
How Often: Once per model
Open Issues: None
1.1.2 IMG-OPT-02 PSF Measurement
Goal: To m
7(TBR)µm and to characterise ghosts.
Outline: A point source is scanned in a fine spatial resolution raster pattern across an area
sufficiently large to sample the PSF.
Equipment Needed: A stable point source, imaged on to the imager FOV via a telescope
simulator
Number of Pixels/Positions: This should be done in several areas of the array, at least one
position in the centre, one at each corner plus one at each edge. If necessary this type of test can
also follow up ghost characterisation discovered by IM-OPT-01
How Often: Once per model
Open Issues: When we come to detailing the tests done, this test may be dropped if we consider
that IMG-OPT-01 alone sufficiently samples the PSF.
1.1.3 IMG-OPT-03 Pupil Scanning
Goal:
and sensitivity to sources near to the OTE primary mirror.
Outline: This test will scan the pupil plane both at the edge of the beam and beyond. If the pupil
is scanned the edge of the beam gives a direct measurement of the angular extent of the beam.
Scanning the point source beyond the edge of the pupil then allows a measurement of out of field
(or external) stray light.
Equipment Needed: Ideally we would sample the pupil plane with a known point source in each
cross-beam direction, finding the edges and characterising the external stray light on all sides of
the beam. The edge of the beam should be fine sampled spatially in order to accurately
determine the beam angular extent, while the out of field measurements can be more coarsely
spaced.
Number of Pixels/Positions: The number of positions in the Pupil plane is TBD but there should
be sufficient coverage to ensure the two goals of this test are met, if necessary, separately. All
relevant filters should be tested.
How Often: Once per model
Open Issues: The MTS design may limit what this test is capable of. The out of field sampling is
likely to be limited to several points on either one direction or two opposite directions. The in-pupil
points at present do not have accurate photometric requirements. Although useful for alignment
TIPS/JIM: MIRI Calibration Plans
James Rhoads (STScI) - October 21, 2004
25
WFC3 TIPS
21 October 2004
Optical
Stimulus
21 October 2004
TIPS at STScI – John MacKenty
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Test Team
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24/7 Support from STScI for Science
leader and Quicklook data analysis.
Scientists:
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QuickLook Operators:
Operations Support:
Mike Robinson
Tom Wheeler
21 October 2004
Howard Bushouse (ICAL lead)
Neill Reid (ICAL Project Scientist)
Sylvia Baggett
Wayne Baggett
Tom Brown
George Hartig
Olivia Lupie
Massimo Robberto
TIPS at STScI – John MacKenty
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Rosa Diaz-Miller
Inge Heyer
Bryan Hilbert
Jessica Kim
Marin Richardson
Jeff Stys
Misty Cracraft*
Helene McLaughlin*
Kevin Lindsay* (new Hires)
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SES Test Configuration
V1
V3
V2
Optical
Stimulus
NOTE: exact placement
of assembly on VIS table
is not final
T/V Shroud
Upper Fixture
Stimulus Offload Arm
Wide Field
Camera 3
Instrument
RIAF Base Frame /
Offload Arm Support
T/V Shroud Base Fixture (NOTE:
additional structure not shown
will support the T/V Shroud
without contacting the VIS)
Vibration Isolation
System (VIS)
Randy Kimble and
Howard Bushouse during
final instrument
inspection
21 October 2004
TIPS at STScI – John MacKenty
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WFC3 Thermal Vacuum Test #1
• WFC3 has successfully completed it first System Level Thermal
Vac test
– Thermal vac test ran from late August until ~10/18 (plan was 10/6)
– Test focused on characterization of:
• Optical performance and stability
• Science performance of Infrared Channel (first real look at this)
• Thermal performance of WFC3 (subject to gravity effects on heat pipes)
– Test obtained
• ~14,000 images (datasets)
• Thermal and power profile information
• We have demonstrated that both the WFC3 Instrument and Team
are functioning well
21 October 2004
TIPS at STScI – John MacKenty
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Positive Accomplishments
• WFC3 operations in realistic environment demonstrated
– Instrument ops and flight software were excellent
– Power margins are good
– Thermal performance generally as expected
• Good margin (3 degrees) on IR detector temperature
• To limits of testing in gravity, heat pipes performing well
– UVIS channel nominal performance (mostly same as ambient)
– IR channel’s first operation
• Backgrounds better than expected from subsystem tests
– Meet specs except perhaps at longest wavelengths (G141, F160W)
• Image quality at or near specification
• Filter ghosts/artifacts within specification
• Detector noise and dark current as expected
21 October 2004
TIPS at STScI – John MacKenty
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Issues Discovered
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Confirmed per-existing issues:
– UVIS filter ghosts unchanged, CCD cross-talk
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New science issues:
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IR detector cross-talk
IR detector baffling (outside field bright source)
IR grisms badly out-of-focus (understood as 90deg rotation)
G141 and F160W have higher than expected backgrounds
IR channel throughput analysis uncertain (30% deficit)
IR detector thermal control outside of specification
IR detector alignment transfer to instrument unsatisfactory
Image drift during thermal slews
• Better than ACS before repair
• Not to spec and probably not to current ACS level
– Features in flat fields in F218W have grown (filter related)
– Calibration system illumination patterns unacceptable (UVIS and IR)
21 October 2004
TIPS at STScI – John MacKenty
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Path Forward
• WFC3 to be removed from SES chamber
– 2 weeks residual work on CASTLE alignment testing
– Ambient check on alignments after WFC3 and CASTLE return to
cleanroom
• Working schedule for compatibility with Robot Mission
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Significant work to fix open liens (e.g. electronics redundancy)
On-going efforts to build improved filters for UVIS
Exploring replacement IR detector (2 prototypes delivered)
Schedule driver is probably HST gyros (June 2006)
System Level Thermal Vacuum Test #2 in October 2006
21 October 2004
TIPS at STScI – John MacKenty
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