TIPS-JIM Meeting
16 February 2006, 10am, Auditorium
1.
2.
3.
Cycle 15 Deadline Statistics
WFC3 Replacement Filters
ASCS CTE Testing for ACS
Brett Blacker
Sylvia Baggett
Marco Sirianni
Next TIPS Meeting will be held on 16 March 2006.
Cycle 15 Deadline Statistics
Brett Blacker
Science Policies Division
Key Points
◊ Proposals slightly up from Cycle 14
◊ Orbits slightly up from Cycle 14
◊ Treasury/Large/AR Legacy requests
about the same
◊ Calibration, Chandra, NOAO, Spitzer
requests about the same
GO Instrument Usage
ACS/HRC
ACS/SBC
ACS/WFC
FGS
NIC1
NIC2
NIC3
WFPC2
Imaging
Spectroscopy
Imaging
Spectroscopy
Imaging
Spectroscopy
POS Mode
Trans Mode
Imaging
Imaging
Imaging
Spectroscopy
Imaging
9.2%
0.6%
2.7%
1.2%
49.2%
0.3%
1.1%
0.1%
2.3%
10.1%
10.1%
0.9%
12.2%
63.1%
1.2%
23.4%
12.2%
TIPS-JIM Meeting
16 February 2006, 10am, Auditorium
1.
2.
3.
Cycle 15 Deadline Statistics
WFC3 Replacement Filters
ASCS CTE Testing for ACS
Brett Blacker
Sylvia Baggett
Marco Sirianni
Next TIPS Meeting will be held on 16 March 2006.
WFC3 Replacement Filters
Sylvia Baggett (STScI)
Ray Boucarut (GSFC)
GSFC
Randal Telfer
Manuel Quijada
Petar Arsenovic
Morgan Dailey
Randy Kimble
Jeff Kirk
Tim Madison
Steve Rice
Jennie Chu
Brad Greeley
Jackie Townsend
Lori Tyahla
Weijun Su
Feb 16, 2006
TIPS – S.Baggett
STScI
Jessica Kim Quijano
Tom Brown
George Hartig
John MacKenty
Massimo Robberto
Barr
George Allen
Kevin Downing
John Potter
15
Outline
• Introduction
• Procurement of replacements
• Characterization of candidates
• Approved filters
• Replacement status
Feb 16, 2006
TIPS – S.Baggett
16
Introduction
WFC3 designed as a two-channel instrument
UVIS Channel
SOFA: 12 wheels, each with 4 filters + clear
63 filters (includes 5 quads, 1 grism)
Flight SOFA
x12
 Excellent performance from 51 of 63 UVIS filters, majority consistent with
spec but instrument level testing showed filter ghosts in some filters
 Procurement of replacements: new technology provides reduction in ghosts
and frequently an improvement in throughput as well
IR Channel
17 filters (15 filters and 2 grisms)
 Excellent performance from all IR filters, consistent with spec; no ghosts
 Procurement of replacements for two filters to add blue blocker (new
substrate-removed IR detector has significant QE in blue); addition of new red
edge coat to grism (G141), to block higher background seen in TV data
Feb 16, 2006
TIPS – S.Baggett
17
UVIS filter ghosts: airgap design
Filter ghosting due to design of element (either air-gap or multi-substrate)
UV and narrowband air-gaps
• Ghosts show elaborate shapes
• Strong field dependence: both
position of ghost relative to source
and morphology of ghost
• Strength varies with wavelength
and peaks outside of bandpass
Flight F225W
~15%
total
Image from WFC3 ISR 2004-04
Feb 16, 2006
TIPS – S.Baggett
18
UVIS filter ghosts:
multi-substrate design
Flight –
monochromatic
VIS/medium bands
• Compact, pointlike ghosts
• Strong wavelength dependence
(strongest out of band)
• Slight field dependence
470nm
500nm
Flight – whitelight
Instrument-level results
<0.1% each
~0.3% total in spots
F606W: multi-substrate construction
Epoxy layer << air gap
AR coating
Coating
Substrate BK7
Epoxy
Coating
Substrate GG435
725nm
Epoxy
Substrate BK7
Coating
AR coating
Brightest spot
~24% peak at 470nm
Feb 16, 2006
Expected
window ghosts
Stimulus artifact
TIPS – S.Baggett
19
Working Plan
With Science Oversight Committee recommendation, focus has
been on obtaining and testing the following new UVIS filters
• UV (F218W, F225W, F275W, F300X)
• F606W
• Medium bands (F410M, F467M, F621M, F689M)
• Narrowbands (F656N, F658N – plus F280N)
Green: high priority
Blue: medium priority
Red: low priority
Feb 16, 2006
TIPS – S.Baggett
20
Manufacturing Process
Process
Manufacturing
Barr Associates, Lead: George Allen
Receive customer
requirements
Design filter
Procure substrate
Check index of refraction
Radiation tests
Polish glass
Verify thickness,
flatness, wedge,
surface quality
Input from GSFC/IPT/SOC
Shape glass
Deposit coatings
Test witness samples
(abrasion, adhesion,
humidity, temperature)
Feb16,
16,2006
2006
Feb
Measure bandpass
And blocking
Inspect and label
selected filters
Search for blemishes, scratches,
Cosmetic defects.
(UV: paint pinholes)
TIPS– –S.Baggett
S.Baggett
TIPS
Predict
ghost level
Ship to GSFC
for
characterization tests
21
7
Characterization Test
Test Flow
Characterization
Receipt of filter
from Barr
Inspection
Tests by vendor (such as thickness, flatness, wedge,
surface quality, bandpass, blocking, cosmetics)
Confirm dimensions; check for blemishes
Front/backlit photos
Whitelight + monochromatic ghost levels
Imaging
Analysis by filter team
Results presented and
discussed (GSFC/IPT)
Wavefront and wedge verification
Focal shift confirmation
Spectral
Scans
Flatfields
Inband scans in 5x5 grid
Out of band scans in 5 positions
Check for coating problems
Environmental tests on
witness pieces
Feb 16, 2006
Feb 16, 2006
Final results posted
to GSFC WWW
SOC/IPT/GSFC
choose flight/spare
Verify no changes
TIPS – S.Baggett
TIPS – S.Baggett
22
8
Example: F225W
Before
After
F225W-303 – images taken in lab at 16 UVIS field points
and mosaic’d together into relative positions on WFC3 FOV
1”
Setup
ghost
200 pixels
Flight – whitelight instrument-level tests
Source in each quad center
Brightest ghost ~10%; totals ~15%.
Filter ghost <0.3%
Feb 16, 2006
TIPS – S.Baggett
23
Approved UV filter set
In all cases, ghosting has been reduced and in most cases, other
improvements were achieved as well such as simplified ghost shapes
(thanks to switch from air-gap to single substrate design), higher grasp,
better uniformity.
Transmission curves of replacement and original flight filters
Feb 16, 2006
TIPS – S.Baggett
Filter
Ghost
Grasp
(spec: 0.2%)
(rel.to
flight)
F218W
10  3.3%
0.55
F225W
15  <0.3%
1.3
F275W
0.7  <0.1%
0.99
F300X
1  0.4%
1.12
24
Approved Medium Bands
In all cases, ghosts have been reduced (or eliminated) and grasp improved.
Original medium band filters consisted of layers of substrates with coatings on both
sides joined with epoxy – giving rise to numerous small, pointlike ghosts. In the new
filters, bandpass coatings are on one side, AR coat on the other.
Transmission curves of replacement and original flight filters
Filter
Feb 16, 2006
TIPS – S.Baggett
Ghost
Grasp
(spec: 0.2%)
(rel.to
flight)
F606W
0.3  <0.1%
1.08
F410M
0.6  <0.01%
1.28
F467M
0.3  <0.01%
1.02
F621M
0.3  0.02%
1.04
25
Installing New F606W
Feb 16, 2006
TIPS – S.Baggett
26
UVIS Filter Status at a Glance
Wheels
Slots
= high
priority
1
F300X
F656N
DONE
DONE
3
4
F225W
F280N
N/A
6
F606W
7
F689M
DONE
8
F621M
F600LP
F218W
F547M
DONE
N/A
9
F275W
11
F467M
F658N
F410M
fatUV
Made
at Barr
Tested
@GSFC
Approved
by SOC
Sent to
Ball
F656N
Legend
replacement
done
deemed not
in progress
worth risk.
Feb 16, 2006
Original F600LPflight
New F280N to go
spare fully tested. New
into F280N slot
filter from Barr to serve
(fatUVs not useful).
as spare.TIPS – S.Baggett
F689M, F658N
replacement
deemed not
worth risk
DONE = old filters removed, new
installed; wheels air-cured and baked
27
TIPS-JIM Meeting
16 February 2006, 10am, Auditorium
1.
2.
3.
Cycle 15 Deadline Statistics
WFC3 Replacement Filters
ASCS CTE Testing for ACS
Brett Blacker
Sylvia Baggett
Marco Sirianni
Next TIPS Meeting will be held on 16 March 2006.
ASCS CTE and QE testing for ACS
M. Sirianni, M. Chiaberge,
M. Mutchler, A. Riess,
T. Wheeler, K. Sembach,
R. Gilliland
M. Sirianni et al.
STSCI-TIPS 2/16/2006
Special Thanks
•
•
•
•
George Chapman
Ilana Dashevsky
Alison Vick
Alan Welty
for their work in successfully planning and
executing program 10771
M. Sirianni et al.
STSCI-TIPS 2/16/2006
Introduction-I
In order to support the decision whether installing the Aft Shroud
Cooling System (ASCS) during SM4 or not, we have been asked to
predict the impact of variations in operating temperature for WFC and
HRC.
A first analysis was conducted last summer using
existing on-orbit data and pre-flight test.
We used our knowledge of performance variation due to
Temperature
Time (on-orbit degradation)
to predict the performance of ACS in 2008 and in 2013 at
three different temperature for the CCDs
(one colder and one warmer than current T)
M. Sirianni et al.
STSCI-TIPS 2/16/2006
Introduction-II
We concluded (see TIPS Oct-2005) that:
1- There is no variation in Read Noise
2- Dark Rate increases significantly running the CCD warmer but
within the temperature range predicted there is no impact on science
3- The number of Hot Pixels increases significantly at warmer
temperature and it is a potential problem (overhead-number of frames)
4- both Dark Current and Hot Pixels improve running the CCD colder
Still, we did not have any data about two main aspects:
Quantum efficiency (expected only minor variations)
Charge Transfer Efficiency
So we planned some on-orbit tests...
M. Sirianni et al.
STSCI-TIPS 2/16/2006
Program 10771
• The program, executed at the end of November,
consisted of three identical sets:
– A:
WFC -80C
HRC -76 C
– B:
WFC -77 C
HRC -80 C
– C:
WFC -74 C
HRC -85 C
• 12 internal + 12 external orbits
• External observations of 47Tuc and one field of GOODS-N
- CTE, QE, impact on science
• Internal observations: Dark, Bias, Flat Field
- reference files, CTE, QE, Dark, Hot Pixels
In the meanwhile, the updated thermal model of HST
predicts that even without ASCS ACS could still
run at the current temperatures….
=> more emphasis on the cold test
STSCI-TIPS 2/16/2006
M. Sirianni et al.
Results : Dark and Hot pixels
•!
•!
•!
Results confirm prediction
Dark Current decrease with Temperature
- no significant impact on science
The number of hot pixels decrease significantly
running the CCDs colder
- potential overheads reduction
- number of readouts
- frequency of annealing
M. Sirianni et al.
-80 C
-77 C
-74 C
STSCI-TIPS 2/16/2006
QE Variations
– Internal flat fields
• After bias level and bias frame subtraction, the
average signal level in the central region is
calculated
• Comparison of count rates at different Temp.
– Stellar photometry
• All Images combined for object coordinate master
catalog
• pairs of images combined for CR-rejection
• photometry (3,5,7 pixels)
• aperture correction (20 pixel WFC, 40 pixels HRC)
• Comparison of magnitudes at different Temp.
M. Sirianni et al.
STSCI-TIPS 2/16/2006
QE Variations
HRC QE Variations
Changes Relative to -80 C
1.040
1.030
1.020
Flat -85
Flat -77
star -85
star -77
1.010
1.000
0.990
0.980
0.970
0.960
0.950
2000
3000
4000
5000
6000
7000
8000
9000
10000
Wavelength (A)
M. Sirianni et al.
STSCI-TIPS 2/16/2006
QE Variations
WFC QE variations
1.020
Changes relative to -77
1.015
1.010
Flat -80 chip1
Flat -74 chip1
Flat -80 chip2
Flat -74 chip2
Star -80
Star -74
1.005
1.000
0.995
0.990
0.985
0.980
4000
5000
6000
7000
8000
9000
10000
Wavelength (A)
NOTE: flat field measurement may be contaminated by light leak during readout
M. Sirianni et al.
STSCI-TIPS 2/16/2006
Results: QE Variations
Results from flat field and stellar photometry are consistent
Variation in QE are:
less than 2 % for WFC
less than 3 % for HRC
•!
Results confirm predictions:
small variations of QE and flat field structures
-
M. Sirianni et al.
no significant impact on science
but require new calibration
STSCI-TIPS 2/16/2006
Charge Transfer Efficiency
•!
CTE
Different traps have different effects depending on their emission time:
- visible tails trailing the objects
- distort PSF
- increase Noise and confusion thus degrading
detection limits
- signal removal
- reduce S/N of detected objects
- degrade detection limit
ANALYSIS:
Deferred charges
Impact on detection threshold
Impact on photometry
M. Sirianni et al.
STSCI-TIPS 2/16/2006
CTE cartoon
100
Perfect CTE
Poor CTE
Few Transfers
Many Transfers
signal level
SAME CTE
0
central
pixel
tail
lost
central
pixel
tail
lost
central
pixel
tail
lost
central
pixel
tail
lost
100
0
central pixel 100
tail
0
------------100
M. Sirianni Total
et al.
central pixel 70
tail
10
------------Total
80
central pixel 95
tail
1
------------Total
98
central pixel 70
tail
10
------------STSCI-TIPS
2/16/2006
Total
80
WFC parallel tails
-80 C
-77 C
-74 C
M. Sirianni et al.
STSCI-TIPS 2/16/2006
Summary: CTE/deferred charges
•!
Changes in Temperature impact
the length and structure of the CTE tails.
The length of the CTE tail is shorter at warmer temperature
The first trailing pixels are brighter at warmer temperature
M. Sirianni et al.
STSCI-TIPS 2/16/2006
Test Description
• Example: SN survey program
Detection limit defined as magnitude of noise peaks
detected and measured as real sources in an image
obtained subtracting two different epochs (4 frames/epoch)
=
Current epoch
M. Sirianni et al.
Master image
Residual image
STSCI-TIPS 2/16/2006
Variation in detection threshold
In condition of High CTE
(few transfers)
we have 3 false detections
at Z=25.45 mag
Low CTE (more transfers)
increases the noise
(more tails)
we have 3 false detections
at Z=25.15 mag
M. Sirianni et al.
High CTE
Low CTE
STSCI-TIPS 2/16/2006
Impact of Temperature
-80 C
-77 C
High CTE
Low CTE
High CTE
Low CTE
-74 C
High CTE
Low CTE
M. Sirianni et al.
Temp
detection loss (average)
-80 C!
-74 C!
-77 C!
0.05±0.05 mag
0.1 ± 0.05 mag
0.15 ±0.05 mag
The combination of
-number of hot pixels and
-length of the CTE tails
changes the noise conditions
STSCI-TIPS 2/16/2006
Summary: CTE/detection Threshold
•!
The variation of detection threshold in
SN survey programs due temperature variations
is due to a combination of:
- change in the CTE tails
- change in number of hot pixels
•!
Surveys program would benefit from running
the CCDs colder. The existing data do not allow
us to easily quantify the improvement.
M. Sirianni et al.
STSCI-TIPS 2/16/2006
Photometric test
Allows to measure the total flux lost and
provide correction formulae for photometry.
Stars are positioned at different distance from the readout
amplifier thus changing the number of transfers and therefore
the impact of CTE.
M. Sirianni et al.
WFC
HRC
STSCI-TIPS 2/16/2006
CTE - WFC photometric loss
T = -77 C (current)
Signal
(e-)
loss*
*%
+/-
prediction*
24 K
1.1
0.3
0.5 ± 0.3
6K
4.0
0.4
1.3 ± 0.7
1.5 K
7.2
0.5
3.2 ± 1.5
*Riess & Mack 2004
**2048 transfers
M. Sirianni et al.
STSCI-TIPS 2/16/2006
CTE - WFC photometric loss
T = -74 C (warmer)
Signal
(e-)
M. Sirianni et al.
loss
%
+/-
24 K
0.9
0.4
6K
3.7
0.7
1.5 K
6.4
1.2
STSCI-TIPS 2/16/2006
CTE - WFC photometric loss
T = -80 C (Colder)
Signal
(e-)
M. Sirianni et al.
loss
%
+/-
24 K
1.3
0.2
6K
3.5
0.3
1.5 K
6.8
0.3
STSCI-TIPS 2/16/2006
WFC Parallel CTE
-80 C
-77 C
Signal (e-)
loss %
+/-
loss %
24 K
1.3
0.2
1.1
6K
3.5
0.3
1.5 K
6.8
0.3
-74 C
+/-
loss %
+/-
0.3
0.9
0.4
4.0
0.4
3.7
0.3
7.2
0.5
6.4
1.2
9
Flux lost (%) (y=2000)
8
7
6
1500 e6000 e24000 e-
5
4
3
2
1
0
-81
-80
-79
-78
-77
-76
Temperature (C)
-75
-74
-73
No variations within the tested temperature range
M. Sirianni et al.
STSCI-TIPS 2/16/2006
HRC Parallel CTE
-85 C
-81 C
Signal (e-)
loss %
+/-
loss %
33 K
4.6
0.5
2.3
4.7 K
4.1
0.9
750
13.7
5.0
-76 C
+/-
loss %
+/-
1.0
1.3
0.9
6.4
1.3
6.6
1.3
10.2
3.0
23.7
5.0
35
Flux lost (%) (y=2000)
30
25
20
750e4700e33000 e-
15
10
5
0
-86
M. Sirianni et al.
-85
-84
-83
-82
-81
-80
-79
Temperature (C)
-78
-77
-76
-75
STSCI-TIPS 2/16/2006
Summary: CTE/impact on photometry
•!
Within the tested range of temperature
we do not observe variation in the total
amount of signal lost.
•!
No variations in the impact on photometry
M. Sirianni et al.
STSCI-TIPS 2/16/2006
Conclusions
Running the CCD colder could be beneficial in terms of
dark rate and hot pixels,
but there is no impact on CTE
and some recalibration is needed due to small QE variations
We can easily run the CCDs a bit colder even without ASCS.
Even without ASCS we can maintain the current temperature.
Given the evaluation of the potential SIs benefits, servicing requirements
and cost the HST project has decided not to install
the ASCS on SM4.
M. Sirianni et al.
STSCI-TIPS 2/16/2006
TIPS-JIM Meeting
16 February 2006, 10am, Auditorium
1.
2.
3.
Cycle 15 Deadline Statistics
WFC3 Replacement Filters
ASCS CTE Testing for ACS
Brett Blacker
Sylvia Baggett
Marco Sirianni
Next TIPS Meeting will be held on 16 March 2006.