TIPS Meeting
20 March 2003, 10am, Auditorium
1. JWST Status
Peter Stockman
2. STIS Status
Paul Goudfrooij
3. Slitless Spectroscopy*
Jeremy Walsh
* No hardcopy provided
Next TIPS Meeting will be held on 17 April 2003.
Space Telescope Science Institute
JWST S&OC
JWST
S&OC Contract
Peter Stockman
TIPS March 20, 2003
1
S&OC Proposal
Space Telescope Science Institute
JWST S&OC
•
Original Proposal submitted November 2001
− Proposed cost comparable to unsolicited proposal, (330M w fee over
10 years)
− Project internal estimate: 140M (based largely on SMEX & MIDEX PI
missions, inexpensive flight ops systems)
− Extended review of proposal assumptions with Project in spring
•
Revised proposal submitted on schedule (16 Sept.) to meet 176M
target. Reductions achieved by the following assumptions:
•
Govt. provides groundstations -- probably DSN
•
Govt. provides I&T test system as basis of flight operations
ground system (STScI was to provide originally)
•
Govt. provides SI, OTE, S/C flight ops analysts for launch + 1 yr
•
Just-in-time development schedule (no phased development to
support SI, OTE, S/C dev.)
•
No operations or science I&T support for SI, OTE, S/C.
•
Reduced support to Project and SIs but w. overguides
2
Status of negotiations (began Jan. 15)
Space Telescope Science Institute
JWST S&OC
•
Contract negotiations began in mid January
− Project puts back: management oversight, Project support,
special studies, PRD Ops. (~ 5M) and fenced these costs off.
− Project poses a new Target of 159.5 (without fee)
− AURA can meet new Project target:
•
•
STScI roles are reduced significantly compared to HST (and
Chandra and SIRTF experience)
» SI support
» Commissioning planning for SIs and spacecraft.
» Calibration software
» Calibration analysis
•
•
Assumes TRW develops I&T system near that needed for
flight ops.
Reduced planning system capabilities: no linked
observations, routine scheduling of parallel calibrations,
manual planning of the weekly calendar
•
Late GO funding for Cycle 1 (Grants office startup delayed)
Contract will be revised after results of replan: reduced
instrument complement?, delayed schedule.
3
Key Assumptions
Space Telescope Science Institute
JWST S&OC
• SI s: The three JWST instruments will have the
capabilities and complexity outlined in the ASWG
and Project Scientists recommendations. In
particular:
-
The NIRCam will be a wide field, infrared camera with a
limited set of fixed-band filter combinations (<20) and several
elements used exclusively for wavefront-sensing.
-
The NIRSpec will be a multi-object, single-order spectrograph
with addressable apertures and a small number of fixedposition gratings (< 6).
The MIRI will have two elements: a camera with a small
number gratings and potentially a fixed pupil mask and Lyot
stop for coronagraphy; a slit spectrograph with R ~1500 and a
small number of fixed-position gratings.
All three instruments will have a single target acquisition
mode (including PEAKUP and/or PEAKDOWN). All three
instruments will have a small number of common readout
schemes (<3) and a common data format.
-
-
4
More Key Assumptions
Space Telescope Science Institute
JWST S&OC
• The S&OC systems will not support parallel activities.
These include parallel calibration, pure parallel or
coordinated parallel observations and parallel modes
within instruments. Level 2 requirement 3.2.15.4 is
applicable to the Observatory.
• The Fine Guidance Sensor will be sufficiently capable
to enable guide star availability and selection to be
done in an automated fashion by the S&OC. This
assumes a wide field, highly capable guider that can
satisfy the Level II requirement (3.2.15.2.2) for the 95%
probability of guide star acquisition.
5
Many Miscellaneous
Space Telescope Science Institute
JWST S&OC
• The peak flight to ground data rate will be 25 GB/day.
• Level 1 data products will be available at L+3 months.
Level 2 data products will be available at L+6 months.
• Targets of Opportunity are not supported within the
time period of this contract.
• Etc. (about 70 such assumptions)
6
Current Status
Space Telescope Science Institute
JWST S&OC
• Technical aspects of contract appear to be
satisfactory to NASA
• 2-3 week period to acquire needed signatures
7
Replan Status
Space Telescope Science Institute
JWST S&OC
• Challenge was to meet:
− Stringent budget limits in FY04-07
− Launch date as close as possible to 2010
− Overall cost of 1.6B
• NASA HQ has settled on Option 4i
− Launch in August 2011
− About 110M cut in US instruments (down from ~ 160M)
• No MIRI
• 1/4 of NIRCam FOV, 1/8 NIRSpect FOV
− Reduced primary mirror area (but meets spec)
− Reduced testing plan
− Challenged Project to save 40-50M in other areas to help
restore instruments.
8
SWG & Project Studies
Space Telescope Science Institute
JWST S&OC
• SWG considering merging NIRCam and Canadian
FGS:
− Potential saving of accommodations (mass, computer)
− Elimination of short wavelength tunable filter
− Shared electronic and detector procurement
• Project finding it difficult to achieve matching
savings
• Other possibilities:
− Loss or reduced short wavelength performance.
− Increased role for ESA in MIRI
• Emergency meeting for SWG in April 10,11
9
SPACE
TELESCOPE
SCIENCE
INSTITUTE
Operated for NASA by AURA
STIS Status Report
Paul Goudfrooij
• Group News / Reorganization
• Unusual Target ACQ Failure
• Items for upcoming Phase II Update
– Planned New Apertures
– Corrections for CTE loss
Group Reorganization
•
Two IS’es on well-deserved sabbatical:
–
•
Jeff Valenti reassigned to JWST / NIRspec (Jan 03)
–
•
But will finish a few STIS assignments
Scott Friedman (COS) helping out with a few tasks
–
–
–
•
Nolan Walborn (Sep 02) and Kailash Sahu (Mar 03)
CCD Dispersion Solutions
CCD & MAMA Spectroscopic Sensitivity Monitors
SM4 Backup to Tom Brown
Claus Leitherer (COS) to help out with
–
Phase-2 reviews of Cycle 12 MAMA programs (if more than
we can reasonably handle in Spectrographs Branch)
TIPS Presentation
March 20, 2003
Paul Goudfrooij
2
Group Reorganization
•
“New” ESA Instrument Scientist: Jesús Maíz-Appelániz
–
–
•
•
•
User Support Lead IS
ETC & APT oversight
New Pipeline Lead IS: Charles Proffitt
New Calibration Lead IS: Linda Dressel
New Information Lead IS: Bahram Mobasher
TIPS Presentation
March 20, 2003
Paul Goudfrooij
3
Unusual Target ACQ Failure
•
Target ACQ of Spectroscopic Sensitivity Monitor Visit on March 6
failed: No Flux in the Lamp Image
1
2
1
2
3
3
Π
•
Ο
∃ direct measurement to measure current across lamp
Hint of lower OCLP30VC, but not statistically significant
Slit wheel / MSM resolver counts identical to other ACQs
Shutter ajmqcb+mncl+ajmqcb sequence occurred nominally
All other mechanisms in their nominal positions
Preliminary conclusion: Lamp did not fire (HSTAR closed)
ACQs after the problematic one were all OK to date
–
•
•
•
•
•
TIPS Presentation
March 20, 2003
Paul Goudfrooij
4
New “Pseudo-Apertures”
•
•
•
•
FUV-MAMA first-order spectroscopy at detector
location with low dark
– ~ 2’’ above bottom of detector
– Reduction of dark current by factor of 5
– 52x0.05D1, …, F25QTZD1
Improvement of Fringe Flats at E1 positions
– Important to align fringes in flat with those in
target spectrum
– 52x0.1 slit (best for defringing) location is
offset in dispersion direction from wider slits
– New ‘E2’ positions will place target slightly
off-center in slits ≥ 0.2 arcsec wide
New WEDGEA0.6 position for 50CORON
Will provide POS TARGs to GOs for cycle 12;
Apertures to be implemented in next APT build.
TIPS Presentation
March 20, 2003
nominal
new
Paul Goudfrooij
5
Correcting CCD Spectroscopy
for CTE Loss
Amp
C
STIS CCD:
Nominal Readout Direction
Amp
D
• 4 Readout Amps (1 / corner)
Nominal Clocking Direction
• Bi-directional Clocking yields
CTI ≡ 1 – CTE:
1 δ(fluxD / fluxB)
CTI =
δY
2
Measured using
“Sparse Field Tests”
TIPS Presentation
Axis2 (Y)
• Nominal Amp: D (lowest RN)
Parallel (virtual) overscan
Amp
A
Serial
overscan
March 20, 2003
Axis1 (X)
Serial
overscan
Paul Goudfrooij
Amp
B
6
“Sparse Field” Tests
•
•
Sparse fields to ensure that sources do not overlap, in
which case (e.g.) PSF wings could fill traps for sources
along the readout direction
Two varieties:
(i) “Internal”
Sparse Field
Test
–
–
Annual series of lamp images through narrow slits,
projected at 5 positions along columns (or rows)
Designed to represent “worst–case” point source
spectroscopy (should be no background to fill traps)
TIPS Presentation
March 20, 2003
Paul Goudfrooij
7
“Sparse Field” Tests
•
(ii) “External” sparse field test (annually)
– A. Imaging:
¬
¬
¬
–
Sparse outer field in NGC 6752
CVZ target (‘cheap’ observing time;
yields range of backgrounds)
3 exposure times; 50CCD mode
B. Spectroscopy:
¬
¬
¬
¬
Young open cluster NGC 346, in
nebulosity
CVZ target
Slitless; 3 exp. times; G430L
[O II] λ3727, Hβ, [O III] λ5007 lines in
nebulosity provide three convenient,
~constant “sky” levels per spectrum
TIPS Presentation
March 20, 2003
Paul Goudfrooij
8
External Sparse Field Test:
Imaging CTI Analysis
Clear dependence on background level (“sky”)
• Slope
systematically flatter
with increasing flux
• “Sky” presumably
fills traps in bottoms
of potential wells,
mostly affecting
transfer of small
charge packets.
• Suggests CTI
bck α
∝ exp –
signal
TIPS Presentation
March 20, 2003
Paul Goudfrooij
9
The Strong Effect of Background:
Gain=1 vs. Gain=4
•
Background level in spectroscopy mode typically low,
dominated by dark current
–
Need to account for spurious charge of the STIS CCD
CC
DR
ead
CC
TIPS Presentation
March 20, 2003
out
sh
D flu
Paul Goudfrooij
10
Functional Dependence on Signal
and Background Levels
•
To be done separately for imaging and spectroscopy
Spectroscopy
Imaging
CCD Column Number
•
•
CCD Row Number
Spectroscopy:
– ISF; ESF in slitless mode
– CCD Sensitivity monitor data
Imaging (cf. Cal. Workshop ‘02):
– ESF & Full-field sens. monitor
TIPS Presentation
March 20, 2003
Paul Goudfrooij
11
Functional Dependence on Signal
and Background Levels
•
Iterative Process for Spectroscopy
– Parameter space covered by ESF test at a given epoch is limited
– Sensitivity monitor: good coverage of signal levels, but not of sky
¬
G230LB data allow suitable cross-comparison with MAMA G230L
AGK+81D266,
G230LB
TIPS Presentation
March 20, 2003
Paul Goudfrooij
12
Time Constant of CTI Evolution
•
•
Need several datasets, each with same signal & background level
Need datasets covering long baseline in time ⇒ ISF data
–
Have to correct for signal & background dependence prior to fitting
60 e–
CTI = CTI0 + { 1 + 0.243 [± 0.016] (t – t0) }
120
180
500
3400
TIPS Presentation
(with t in yr)
CTI data from Tom Brown
March 20, 2003
Paul Goudfrooij
13
Final CTI Correction Formula
(For Point-Source Spectroscopy)
•
Define background (sky) and epoch parameters:
yr = (MJD – 51765.25) / 365.25
(i.e., relative to 2000.6)
bg = max(BACKGROUND,0) + 0.5 for CCD Gain = 1
+ 5.0 for CCD Gain = 4
•
Functional form producing best fit to the data:
(
CTI = 0.0467 GROSS – 0.720 ∗ exp –3.85
•
bg
GROSS
0.17
)∗ (1 + 0.243 yr)
Implementation into the pipeline:
¬
¬
Formula parameters into CCD table reference file (new columns)
1-D extraction step (x1d) to correct for CTE by default for CCD data
(CTE correction step switchable)
• For Cycle 12 Phase II, provide downloadable IRAF script to
calculate correction factor for a given net & background level.
TIPS Presentation
March 20, 2003
Paul Goudfrooij
14
Quality of CTI fit
CTI Correction good to ≤ 7% ⇒ Spectrophotometry good to ≤ 1%
@ 2000.6
TIPS Presentation
March 20, 2003
Paul Goudfrooij
15
The Strong Effect of Background:
Gain=1 vs. Gain=4
Complex behavior at low signal levels
–
–
–
CTE-like behavior obvious, but details not quite understood
Notice somewhat different behavior for B vs. D amps
Renders low-signal CTI values somewhat uncertain
TIPS Presentation
March 20, 2003
Paul Goudfrooij
16