TIPS-JIM Meeting
20 July 2006, 10am, Auditorium
1.
ACS Side-2 Performance Update
Ken Sembach
2.
Time-Dependent Spectraol Traces
for the STIS First-Order Modes
Linda Dressel
3.
Modeling the Point Spread Function
for JWST
Colin Cox
Next TIPS Meeting will be held on 17 August 2006.
ACS Side-2 Performance Update
STScI TIPS Meeting
20-July-2006
Ken Sembach
1
ACS Timeline
Date (2006)
Event
June 19
ACS suspends at 17:15 UTC. Tiger Team formed.
June 20
ACS Suspend Status Meetings start.
Analysis of ACS data prior to suspension shows that it looks normal.
SMOV preparations begin in case switch to Side-2 is necessary.
June 21
ACS CEB Anomaly Review Board created.
June 22
Observing timeline intercepted with SMS containing no ACS activities.
Tiger Team passes off investigation to ARB.
ACS transitioned to Operate mode on Side-1 as recommended by TT.
June 23
ACS Team decides to recommend WFC temperature setpoint change.
June 27
ARB recommends switch-over to Side-2.
ARB endorses WFC temperature setpoint change.
June 29
FRR for switch-over to Side-2 held - Switch-over approved.
New FSW uploaded to ACS.
June 30
Uplink and realtime switch to Side-2. CCD electronics boards powered.
ACS safed for SMS intercept on July 2.
2
ACS Timeline (continued)
Date (2006) Event
July 2
Intercept of SMS with ACS activities.
July 3
Successful checkout of ACS memory / dumps.
July 4
WFC temperature setpoint lowered from -77 C to -81 C.
Successful resumption of CCD calibration and science observations.
July 7
ARB lifts moratorium on SBC observations.
ARB considers risks/benefits of ACS Side-1 testing.
July 11
ARB votes that risks to ACS assets outweigh benefits of Side-1 testing.
July 12
Press release for first Side-2 science observation released.
July 13
HST Project concurs that Side-1 tests should not be done at this time.
July 16
SMS contains SBC SMOV activities.
July-August Analysis of SMOV / science data in progress.
3
ACS Suspends
• What was observed
• All ones were read back from WFC and HRC CCD Electronics Box
(CEB) A/D telemetry FIFOs
• Status buffer messages : +15V and +5V supply voltages at high limits
• 36 CEB limit-checked parameters were found to be out-of-limits
• ACS current decreased 1.2-1.8 amps (no current spike in ACS)
• Anomaly lasted about 7 seconds before ACS suspended
• Ruled out
•
•
•
•
WFC and HRC CEB interface optocouplers in common package
WFC and HRC CEB FIFO read control
CEB A/D converters
Space weather-induced damage (excessive radiation)
4
CEB Power Switching
All relays independent and switched by individual RIU commands
LVPS1
ASPC1
(video)
MEB2
ASPC2
(video)
Clock1
(CCD control)
MEB1
LVPS2
Clock2
(CCD control)
Timing
(main control)
CEB
All boards are needed for operation of the entire detector.
Single fault affects at most half the science data.
One CEB each for WFC and HRC
Simplified – multiple diode
busses in hardware
Legend:
5V only
5
Anomaly Review Board Investigated Possible Failures
Case
#
Failure Mode
Anomaly
match
based on
ETU
testing
Implicates
Expected Telemetry
+5V
+15V
-15V
+35V
+5V
+15V
-15V
+35V
1
All Nominal
No
Problem intermittent or
+15V open beyond TLM
sample point
2
+15V open
(external)
YES
LVPS #3 Board
+5V
0V
-15V
0V
3
+15V open
(internal)
YES
MFL2815D
+5V
0V
-18V to
-20V
0V
4 or 5
6
7
8 or 9
-15V open
(external or
internal)
+15V
shorted
(internal or
external)
-15V shorted
(internal or
external)
No
MFL2815D or LVPS #3
+5V
+15V
0V
+35V
YES
MFL2815D or LVPS #3 or
MEB Backplane or
Harness to CEBs
+5V
0V
-6V to
-8V
0V
No
MFL2815D or LVPS #3 or
MEB Backplane or
Harness to CEBs
+5V
+8V to
+11V
0V
+30V to
+35V
MFL2815D
inhibited or
internally
destroyed
No
(additional
testing in
progress)
MFL2815D
+5V
0V
0V
0V
Fault within MFL2815D
Fault on LVPS #3 Board, not in MFL2815D
Fault mode matches on orbit anomaly signature
6
ACS Resumes Exploration of the Universe
7
ACS Side-2 Orbital Verification Programs
Program
Analysis
10735
Cox
SBC MAMA Recovery
4 (I)
10737
Mack /
Gilliland
CCD Stability Monitor
5 (E)
10738
Program Name
Mack /Bohlin Earth Flats
10752
Sahu / Lallo
11005
Sirianni /
Lucas
11006
Cox
11007
Welty
11008
Sirianni
11009
Welty
Orbits
2 (I)
Cycle 14 Focus Monitor
1 (E)
Functional Test - MEB2 Switch
35 (I)
SBC Filter Wheel Checkout
7 (I)
ACS Side 2 Dump Test and Verification of ACS
Memory Load
1 (I)
ACS CCDs Side-2 Temp Setpoint
4 (I)
ACS Science Data Buffer Check/ Self-Tests for
CS Buffer RAM and MIE RAM
8 (I)
8
ACS WFC Temperature Setpoint Change
• HRC TEC setpoint maintained at -80 C
• WFC TEC setpoint lowered from -77 C to -81 C after Side-2 switch
• Lower WFC setpoint should improve science
• 2005 Aft Shroud Cooling System study
• Fewer hot pixels (and fewer anneals needed)
• Shorter charge transfer tails
• Gain in sensitivity for deep exposures is ~ 0.1 magnitudes (or
equivalently, about 20% in observing time)
• Lowering temperature now consolidates recalibration activities for
Side-2 switch and temperature change
• Change would likely have been needed within the next 12-24 months
9
Dark Current / Hot Pixels
WFC1
Side-2 (-81 C)
Side-1 (-77 C)
WFC2
Side-2 (-81 C)
Side-1 (-77 C)
Note: The white histogram is wider because only 4 images were used instead of 40. In both cases the tail of the
histogram is for 1 single day, the first day after the anneals of July 14 (white) and June 15 (yellow).
WFC1
WFC2
Dark Current: (e/pix/hr)
Side-2 (-81 C)
Side-1 (-77 C)
10.2
18.4
8.6
15.7
Ratio
(-81 C / -77 C)
0.55
0.55
10
WFC Hot Pixel Contamination (%)
Threshold
(e-/pix/sec)
Side1
(-77 C)
Side2
(-81 C)
(-81C /-77C)
>0.01
22.2
9.0
0.41
>0.04
3.8
1.3
0.34
>0.08
1.6
0.6
0.37
>0.10
1.1
0.5
0.45
Ratio of Hot Pixels (-77 C / -81 C)
Ratio
Side-1 (-77 C)
Side-2 (-81 C)
Note: 100x80 pix region, first day after annealing (only pixels brighter than 0.08 are shown)
11
Gain Ratio
• WFC: Gain=1 and Gain=2 (default)
• Side-2 Ratio
• Same as on Side-1 to 1 part in 104 (47 Tuc data)
• Quad-quad gains are consistent to 1 part in 103
(internal flats)
12
WFC Bias Jumps
A
Typical case
A
B
B
1 DN
C
C
D
D
Image stretched to show bias jumps.
1 DN
13
WFC Bias Jumps
A
Worst case
A
B
B
1 DN
C
C
D
D
Image stretched to show bias jumps.
1 DN
14
WFC Bias Jumps
• WFC
• Side-1 (Gain=2, default)
• Jump detected in 1/40 images
• Jump detected only on Amplifier B
• Side-2 (Gain=2, default)
• Jump detected in 7/35 images
• Jump detected on 2 or 4 amplifiers simultaneously
• Side-2 (Gain=1)
• Jump detected in 5/35 images
• Jump detected only on 1 amplifier at a time, mostly Amp B
• HRC
• No bias jumps observed on Side-1 or Side-2
15
Sensitivity
• Small sensitivity decrease
(expected) seen after lowering WFC
setpoint
• Sensitivity measured using stellar
photometry and internal flatfields
Filter
Gain
Side-2 Change in QE
F435W
2
F475W
2
-2.1%
F606W
1,2
-1.2%
F625W
2
-0.9%
F775W
2
-1.1%
F814W
1,2
-2.6%
-1.1%
-2.2%
(Internal)
-1.7%
(Internal)
A 4096x4096 composite WFC/F606W image of a
portion of globular cluster 47 Tuc obtained on
Side-2 (4 x 339 sec).
16
Point Spread Function
•Astrometric and photometric analysis of WFC Side-2 47 Tuc data (J. Anderson)
• Temporal change noted was well within normal orbit-orbit and epoch-epoch ranges
• No evidence for additional underlying spatial dependence of PSF
Constant Library
Library + Perturbation
Empirical library PSF
for WFC/F606W
On average, 22.4% of light falls in
central pixel (+15%, -12%)
-1
+3
-1.0
-5
+1
-0.5
+6
+2
+0.3
+7
+3
+0.5
% Residual
Photometry
supported
to 0.005
mag
Astrometry
supported
to 0.01 pix
in
both x and y
Same as
on Side-1
17
Mechanisms Affected by Side-2 Switch
• Fold mirror / cal door / coronagraphic spot
• Resolvers and electronics
• Positions are within usual ranges seen for Side-1 motions.
• Filter wheels
• Resolvers and electronics
• Filter Wheel #1: positions are the same as on Side-1
• Filter Wheel #2: currently a small offset w.r.t. Side-1 (investigating)
• Shutter
• LEDs, photodiodes, and electronics
• No test performed yet
• Post-flash illumination
• LED
• No test performed yet (low priority)
18
Coronagraphic Spot Position
Side-2
Motion on Side-2
is well within
historical Side-1
envelope of positions.
19
Time-Dependent Spectral Traces
for the STIS First Order Modes
Linda Dressel (INS)
with Don Lindler, Ralph Bohlin, Phil Hodge, Nadia Dencheva, Sherie Holfeltz
Trace tilt evolution
Trace shape
New traces
New evolution code
Bimodal behavior
Remaining work
STScI TIPS
20 July 2006
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
1
A grid of reference file traces is placed on an
(flt, crj) image as the framework along which
interpolation will be done to produce spectral
extractions (x1d), rectified images (x2d)
Problem: x2d images still have some tilt
Row does not come from one location along the slit
 Random changes, systematic changes in traces?
STScI TIPS
20 July 2006
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
2
The tilt of the traces has been
evolving steadily over time,
showing clockwise rotation on
the detector
G430L spectral traces at the center
of the detector over the lifetime of
STIS, along with the reference file
trace
STScI TIPS
20 July 2006
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
3
Rotation rates of the CCD L grating traces
(positive = clockwise)
GRATING
STScI TIPS
20 July 2006
ROTATION
RATE (deg/yr)
G140L, high
0
G140L, low
-0.0030
G230L
+0.0005
G230LB
+0.0030
G430L
+0.0041
G750L
+0.0037
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
4
CCD traces have the same shape:
Trace minus linear fit for G230LB, G430L, G750L,
G750M(6581, 6768, 8561)
STScI TIPS
20 July 2006
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
5
New traces (rotated as needed)
 Improved trace reference files for L modes
(delivery imminent) with specified MJD, rotation rate
G140L: 6 feb 1999, CAL/STIS 7937 (o53001*) GD71 (1 star, 20 steps along slit)
G140L, USEAFTER Oct 01 1996 (for aperture at ~ +3")
G140L, USEAFTER Mar 15 1999 (for aperture at ~ -3"): rotated to compensate
for MSM change
G230L: 2 Sep 1997, CAL/STIS 7667 (o46j01*) NGC346-368 (3 stars, 8 steps)
G230L
G230LB: 13 Feb 1998, CAL/STIS 7665 (o45p02*) HD120315 (1 star, 33 steps)
G230LB
G430L: rotation of G230LB
G750L: rotation of G230LB
STScI TIPS
20 July 2006
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
6
New Code:
OPUS 2006.4, including CALSTIS 2.21b (released 28 June 2006)
STSDAS, including CALSTIS 2.21b (to be released in fall 2006)
CALSTIS 2.21b reads two new columns in the SPTRCTAB:
• MJD
• DEGPERYR (rotation rate; 0 if not measured for that grating/cenwave)
It reads the MJD of the science exposure.
It computes the difference in dates and the consequent trace rotation.
It applies that rotation to the traces before applying them to the (flt,crj)
image.
STScI TIPS
20 July 2006
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
7
Comparison of “traces” made from x2d files: G140L (low position)
OLD REDUCTION: EARLY, LATE
STScI TIPS
20 July 2006
NEW REDUCTION: EARLY, LATE
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
8
Comparison of “traces” made from x2d files: G430L (center)
OLD REDUCTION: EARLY, LATE
STScI TIPS
20 July 2006
NEW REDUCTION: EARLY, LATE
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
9
COMPLICATION!
In this case, there are two
evolutionary tracks of trace tilt
vs time, both showing clockwise
rotation on the detector
G750M(6768) spectral traces at
the center of the detector over
the lifetime of STIS, along with
the reference file trace
STScI TIPS
20 July 2006
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
10
• Grating tilt is set by 3 cylinders
• Cylinder settings were changed on July 21, 1997
• Only one exposure in G750M(6768) plot had the early settings
• Virtually all STIS GO data have been taken after the change
Plot: SHIFTA2 vs date
(square: low evolution track, triangle:
high evolution track)
Population on the two evolutionary
tracks of trace tilt vs time is
predicted by SHIFTA2, the
measurement of the Y position of
the wavecal image on the detector
The higher track is very rarely
populated by exposures with central
wavelengths 6581, 8561
STScI TIPS
20 July 2006
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
11
Remaining Work
• Delivery of the new trace reference files for the L
modes
• Completion and delivery of new trace reference files
for G750M(6581), G750M(6768), G750M(8561)
• Implementation of a "tweak-trace" post-processing
tool that measures the science image to determine the
rotation to apply to the reference file traces
• Completion of an Instrument Science Report
STScI TIPS
20 July 2006
Time-Dependent Spectral Traces for the STIS First Order Modes
Linda Dressel (INS)
12
Point-spread Function
modeling for the James Webb
Space Telescope
Colin Cox and Philip Hodge
Space Telescope Science Institute
20 July 2006
TIPS/JIM
1
Objectives
●
●
●
20 July 2006
Provide a model of the JWST PSF for general use in
subsequent image simulation.
Should be generally available and useable on
computers most users will have without expensive
license fees.
Be expandable to incorporate telescope and
instrument data as it becomes available.
TIPS/JIM
2
Design decisions
●
Program written in Python.



●
Input and output in FITS format tables and images.



20 July 2006
Generally available and free.
A language which is gaining increasing acceptance for its flexibility
and ability to incorporate software written in other languages.
Includes a GUI (Tkinter) which makes it fairly easy to provide an
intuitive interface.
Has been in use in astronomy for many years.
Allows use of data produced by other programs.
Allows use of output in other programs.
TIPS/JIM
3
… Design Decisions
●
Graphics use Matplotlib.

Freely available as Python library.


Easy to use and provides interactive plots with ability to export
resulting images.

20 July 2006
Based on Matlab.
Use of Matplotlib is not required for this software. Calculations can be
performed and FITS files produced without viewing intermediate
results.
TIPS/JIM
4
In the Fraunhofer region, the complex image produced by a converging spherical
wave of wavelength λ is
ψ=
∫
Ae−ikr dS
integrated over the wavefront S, where A is the complex amplitude at any point on
the wavefront, k = 2π/λ and r is the distance from a point on the wavefront to the
image position.
Variations in r are expressed as optical path differences d(x,y) and the overall
distance adds only a constant phase.
The extent and amplitude is described by the pupil image and the integration
becomes
€
ψ (u,v) =
20 July 2006
€
∫∫ e
−
2 πi(ux +vy )
λ
TIPS/JIM
P(x, y)dxdy
5
The integral
ψ (u,v) =
∫∫ e
−
2 πi(ux +vy )
λ
P(x, y)dxdy
Is recognizable as a two-dimensional Fourier transform involving the
phase and amplitude of the pupil function. The pupil function P is
obtained
from the aperture and optical path difference files as
€
P(x,y)=A(x,y)e2πid(x,y)/λ
The image intensity at the focus is then the power |ψ|2 The phases are
obtained from the optical path differences divided by the wavelength.
20 July 2006
TIPS/JIM
6
Model amplitude and phase of pupil function for JWST.
For the amplitude figure on the left, zero is black, while for the optical
path differences zero is mid-grey
20 July 2006
TIPS/JIM
7
Source of OPD files
●
Produced by Ball Aerospace


●
●
●
Error budget incorporated to match Level 2
requirements (Revision R)
Total RMS error (OTE + ISIM + NIRCam)
~140nm
Some remaining inconsistencies

20 July 2006
Geometrical Modeling program OSLO
Scalar diffraction generated by program IPAM
Secondary mirror supports modeled at twice the
proper size
TIPS/JIM
8
Image Scales
●
●
●
20 July 2006
The angular size of the output elements is
λ/D radians where D is the pupil diameter as
represented by the size of the OPD array.
For JWST D is about 6.5m which leads to a
size of 0.032 arcsec at one micron.
We can increase the sampling factor by
embedding the pupil array in larger arrays,
surrounding the nominal array with zeros.
TIPS/JIM
9
Pupil arrays and
Oversampling
4X
2X
20 July 2006
TIPS/JIM
10
Wavelength Weighting
●
Two ways to select wavelength coverage


Enter minimum and maximum wavelengths plus
number of steps. A single step gives the
monochromatic case.
Use a source spectrum and a filter function



20 July 2006
Spectrum may be supplied directly as a file or chosen by
the software based on stellar type.
The stellar type drives the selection from a library of
Kurucz model spectra supplied with the software.
Filter throughput function may be a user supplied file or
picked from a set of filter names
TIPS/JIM
11
Program Menus
20 July 2006
TIPS/JIM
12
Calculation details
●
●
●
20 July 2006
Program integrates the product of source
strength and throughput across bandwidth
subdivided into a chosen number of sections.
PSF calculated at the center of each subband and combined according to integrated
weights.
Element size is wavelength dependent so
each monochromatic PSF is resampled onto
a common size in arcsec.
TIPS/JIM
13
Bandpass Weighting
Weights across F210M filter
Source Spectrum
20 July 2006
TIPS/JIM
14
Calculated PSFs
Broad band
1 to 2 microns
Wavelength 2 microns
Wavelength 1 micron
20 July 2006
TIPS/JIM
15
PSF Profiles
Unaberrated
Strehl=1.0
Aberrated
Strehl=0.8
20 July 2006
TIPS/JIM
16
Encircled Energy
Plausible aberrations with Strehl ratio
of 0.8. 80% of energy falls within
0.17 arcsecond radius
20 July 2006
Unaberrated case obtained by setting
Optical path differences to zero
80% of energy within 0.12 arcseconds
TIPS/JIM
17
Detector Effects
Pixel sampling
20 July 2006
TIPS/JIM
18
Detector Effects
Noise and charge diffusion
Assumed 0.01 counts per second per pixel dark noise and 10 electrons readout.
Pixel-to-pixel charge diffusion of 1%
20 July 2006
TIPS/JIM
19
Detector Effects
Noise and charge diffusion
20 July 2006
TIPS/JIM
20
http://www.stsci.edu/jwst/software/jwpsf
20 July 2006
TIPS/JIM
21