Instruments
Division
October 2003 Highlights
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JWST Branch
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JWST Highlights for October 2003 – ISIM and Instrument
Support
* Nelan,
McCullough, Meixner, and Valenti published a memo summarizing the instrument
requirements for small-angle offsets with JWST (TPRR 1001). See http://www.stsci.edu/jwst/docs/tm/TM-2003-0015-A_0743.pdf
o Offsets < 0.5 arc sec must be accurate to 5 mas
o Offsets 0.5—20.0 arc sec must be accurate to 7.5 mas (to support NIRSpec dithers and target acqs)
o Raised concern with NIRSpec PI (Jakobsen) that the project is not taking a strong science advocacy position in favor of the latter requirement (since it will cost more).
* Meixner published a memo on sub-array requirements for MIRI: http://www.stsci.edu/jwst/docs/tm/TM-2003-0016-A_1005.pdf
* All parties signed the official v1.0 of the NIRCam Ops Concept.
* James Rhoads discussed a first draft of the Tunable Filter Ops Concept with the Canadians.
* McCullough and Meixner prepared SRR presentations of the NIRCam and MIRI Ops Concepts, respectively, and supported dry runs.
* Jerry Kriss prepared a lexicon and description of detector readouts for JWST. This will become a part of the Mission Ops Concept Document.
* Kriss reviewed RIDs submitted by the science teams and instrument scientists on the SI sections of the Mission Ops Concept document.
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ACS + WFPC2 Branch
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SELECTED HIGHLIGHTS
*
Geometric
distortion solutions from the outsourcing program by Anderson & King have
been used in UDF reductions with excellent results.
*
A new suite of
flat fields to cover special cases of filter wheel offsets in cases having dust
motes have been delivered for pipeline use.
Pipeline / Analysis Software
*
Testing of the
Anderson & King geometric distortion solution, coupled with recoded drizzle
routines to incorporate have shown excellent results and application to UDF
reductions is in place.
*
Support for the
new release of STSDAS 3.1 with significant PyRAF updates, and the associated
MultiDrizzle in a beta-level release has been a primary focus.
*
Redesign
efforts are underway that will allow MultiDrizzle to be packaged directly with
STSDAS.
User Support
*
The UDF
observations are confirming the need for attention to several ongoing
calibration efforts in the group to provide improved treatment of
quadrant-to-quadrant bias changes, understand and correct as possible amplifier
cross-talk, update data quality flags for charge traps, and provide updated
flat field, bias and dark reference files.
Documentation
*
ISRs released:
o
ACS ISR 03-11:
Flat Fields for Filter Wheel Offset Positions
(Bohlin, Wheeler, and Mack)
*
A near final
draft for new release of the ACS Data Handbook is under review.
Calibration
*
Confirmation of
the outsourced geometric distortion solutions has been obtained.
*
Spectrophotometric
observations of Vega have been obtained to support interpretation of similar
observations of the Sloan fundamental standard that will be used in conjunction
with existing ACS sloan filter set photometry to establish effective cross
calibration.
*
Determination
of "hyper"-darks and -biases using extensive sets of input frames are
under investigation for expected delivery and use with HDF analyses where the
co-addition of a huge number of images would benefit from such improvements.
*
Analysis of sky
flats for all UDF filters is actively underway, an undertaking that involves
analysis of several hundred orbits worth of ACS/WFC images of sparse fields
with specialized reductions to ignore the astronomical objects usually of
interest in order to determine the detector imprint on truly blank fields as
required of a flat field. These results
are being compared with improved L-flats from analysis of dithered, and rotated
observations of a stellar field.
Team/Management Issues
*
Redefinition of
tasks within the recently merged ACS and WFPC2 branches has continued with the
addition of two scientists, Andy Fruchter and Marco Sirianni and the transfer
out of DA support from Gabe Brammer and (part of) Max Mutchler.
Other
*
The impact of
2-gyro operation on Earth calibrations has been discussed, and is viewed as not
likely to have a deleterious impact on these.
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COS Branch
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SELECTED
HIGHLIGHTS
*
Thermal-Vac
science calibration ("Appendix B") work was completed at Ball.
*
Nearly 2600 COS
Thermal-Vac (T-V) science calibration exposures have been automatically
processed through OPUS, stored in the HDA, and available for retrieval via
StarView screens. The entire FUV and
NUV science calibration program has been completed and archived.
*
STScI continued
to provide important expert support of SI optical alignment with RAS/Cal for
vacuum and nitrogen purge activities.
*
STScI IS and DA
supported COS T-V science calibration in regular shifts as data analysts at
Ball.
*
COS parallel
exposure requirements definition and implementation strategy was
completed.
DETAILED
ACTIVITIES
Instrument Status:
*
Vacuum tank
pressure dropped to an acceptable level for FUV detector HV operation and COS
thermal-vacuum science calibration resumed on 10 Oct at Ball Aerospace in
Boulder, CO. All FUV science
calibration in vacuo activities, subsequent RAS/Cal re-alignment, and remaining
NUV resolution tests and instrument repeatability monitor tests under nitrogen
purge were completed by 23 Oct.
*
Following
completion of vacuum science calibration of COS, the SI ion pressure gauge was
repaired and successfully tested.
IDT / SI Support - COS Thermal-Vacuum Testing
Support:
*
COS
far-ultraviolet channel (FUV) Thermal-Vacuum (TV) Science Calibration
activities were conducted and concluded this month. NUV spectral resolution tests were performed under nitrogen purge
at the end of vacuum science calibration activities. FUV alignment and calibration programs executed included those for
sensitivity, flatfield, scattered light characterization, spectral resolution,
mechanism stability, and geometric correction.
*
STScI COS
Instrument Scientists (IS) Ken Sembach, Scott Friedman, Ralph Bohlin, Claus
Leitherer, George Hartig, and Tony Keyes and data analyst David Stys supported
a variety of operational shift activities onsite at Ball. Onsite support includes continuing analysis
of test data, maintenance of test summaries, creation of shift logs, and
participation in the drafting of new and revised test activities and
procedures. Hartig maintained a
flexible schedule floating throughout testing, and Keyes, Leitherer, Sembach,
Friedman, and Bohlin stood regular shifts at Ball as data analysts in support
of science calibration programs to determine instrumental throughput,
flatfields, mechanism stability and repeatability, and spectral
resolution.
*
Throughout
science calibration activities IS George Hartig continued to support testing
and analysis with particular regard to optical alignment issues. He consulted onsite with the team and
directly participated in stability test development. Following FUV vacuum science calibration he participated in
RAS/Cal alignment activities which improved the spot size and alignment of the
chief ray input into COS, which affects the capability to verify NUV resolution
at the shortest wavelengths.
Subsequently NUV resolution verification tests proceeded successfully
under nitrogen purge.
*
IS Ralph Bohlin
analyzed high S/N NUV flatfield and absorption cell science calibrations
on-site at Ball. He produced an initial
NUV P-flat suitable as a reference file showing 1.36% rms Poisson variation and
3.25% rms intrinsic detector scatter.
Additionally, he verified that special absorption cell observations yield
1% rms per continuum pixel and 0.6% rms per resolution element.
*
Keyes performed
an initial analysis onsite at Ball, which verified that NUV spectral resolution
longward of 1800 Angstroms meets specification.
*
Nearly 2600
calibration exposure files were obtained during Thermal-Vacuum testing and all
have been successfully transferred to STScI, processed by OPUS, and archived in
the Hubble data archive. Keyes,
Sembach, Hartig, Friedman, Phil Hodge and DA Matt McMaster evaluated and
resolved keyword and file structure anomalies in the processed data.
Ground System Development:
*
The COS
Front-end Implementation Group (COS FIG) has concluded the definition of
important updates to the STScI scheduling system that will allow the efficient
execution of observations in parallel with the standard COS TIME-TAG data
taking mode, with COS as either the prime instrument or the parallel
instrument. This capability was
previously not available for any HST TIME-TAG observation. This effort has clearly illustrated the
utility of the cross-disciplinary concept inherent in the FIG; creative efforts
by developers, system engineers, and scientists working together has made it
possible to implement this new capability.
User Support:
*
The revised COS
mini-handbook version 2 was distributed with the cycle 13 Call for
Proposals.
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NICMOS Branch
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SELECTED
HIGHLIGHTS
* SAA-Clean Tool (IDL version) available to GOs, through NICMOS Website
DETAILED ACTIVITIES
Instrument Status/Characterization
* NICMOS detectors' temperature have recently increased to ~77.2 K, about 0.05 K higher than the desired detectors' temperature. This is expected as we approach the warm season. A request has been submitted by the NICMOS group to decrease the setpoint temperature by 0.05 K to maintain the desired detectors' temperature of 77.15 K. The request has been accepted, and will be implemented at the first opportunity.
Calibration/Pipeline
* An IDL routine created by the NICMOS group to help alleviate the effects of post-SAA cosmic ray persistence on science images has been posted on the NICMOS Website. The routine exploits the availability of the post-SAA Dark Images (automatically executed after each SAA passage) to derive the level and decaying rate of the cosmic ray persistence; the algorithm then derives a proportionality factor to be applied to those darks, and uses the rescaled darks as `cosmic ray maps' on the science images to alleviate the persistence. Work is ongoing in the Software Group (Vicky Laidler) to transfer this algorithm to an ST-supported STSDAS tool.
User Support
* Work is ongoing on the Grisms ETC for NICMOS. A number of test cases are being created to allow testing of the preliminary version of the ETC.
* A total of 19 NICMOS GO programs (4 Cycle 11 and 15 Cycle 12) and 4 SNAPs (1 remaining Cycle 11) have executed since July 2003; among those the first epoch of Thompson's NICMOS UDF (9803). The second epoch of this program has started execution.
Documentation
* ISR-NICMOS-2003-010: Removal of Cosmic Ray Persistence from Science Data using the Post-SAA Darks, Bergeron & Dickinson
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Spectrographs
Branch
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SELECTED HIGHLIGHTS
*
New, more
accurate distortion corrections for the NUV-MAMA detector.
*
Time dependent
sensitivity corrections for CCD spectroscopy.
Pipeline/Calibration
*
The
Spectrographs group has derived and delivered to the HST archive a new table of
geometric distortion coefficients for NUV MAMA imaging modes. These were
derived by comparing STIS NUV-MAMA images taken with the F25CN182, F25CN270,
and F25SRF2 filters with WFPC2 F170W and F336W images of the same fields,
thereby transferring the well-established astrometric solution for the PC to
STIS. With this new solution, typical median errors between the predicted and
the real positions were found to be in the range of 0.28 to 0.53 MAMA pixels
(7-13 mas). As a comparison, the older geometric distortion table produced
median errors of a few MAMA pixels. We hope to complete similar revisions for
the FUV-MAMA and the STIS/CCD distortion coefficients in the next few months.
*
The
Spectrographs group has also completed a new TDSTAB reference file that now
allows CALSTIS to correct the calibrated fluxes of CCD spectral observations
for time dependent changes in STIS sensitivity (note that similar corrections
for 1st order MAMA modes were implemented in May of 2002). The correction is as
large as 2% per year at the shortest wavelengths of the G230LB grating. This
change will be implemented in the pipeline as soon as the rules for populating
reference file names in the data headers can be updated to allow CCD
observations to access the new TDSTAB file.
Instrument
Status/Operations
*
Routine
analysis of STIS ACQ data showed that on September 25 the HITM1 lamp failed to operate
during an target acquisition exposure, resulting in a failure to properly
acquire the target and place it in the science aperture. All science from this
visit was apparently lost. This problem had occurred twice previously (March 2
and April 6, 2003). In response to those earlier failures, starting on 12 May
the default HITM1 lamp current for ACQ exposures had been increased from 3.8 to
10mA. Until this latest failure, it had been thought that this change had
solved the problem. Investigation and consideration
of additional operational changes to work around this problem are ongoing.
User Support/Documentation
*
On October 28,
the Spectrographs group issued a new Space Telescope Analysis Newsletter (STAN)
for the STIS instrument. This STAN
details the improvements to the calstis software that were implemented in
calstis 2.15b, which was released with STSDAS 3.1. The STAN also discussed the new version of the STIS IHB for Cycle
13, and the improved geometric distortion coefficients recently delivered for
the STIS NUV-MAMA.
Personnel
*
During
September Alessandra Aloisi joined the Spectrographs group. Tom Brown and
Bahram Mobasher continued to reduce their work for the Spectrographs group as
they transition to the WFC3 and NICMOS groups respectively.
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WFC3 Branch
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SELECTED HIGHLIGHTS
*
Science IPT is
supporting the UVIS (CCD) detector noise testing at GSFC. This first fully integrated system test is
proceeding very well with both sides of the instrument delivering ~3 e- noise
level (at the CEI goal!). STScI pipeline processing of data from these tests
has been functioning well.
*
Kutina and Reid
continue to prepare the calibration data ground system and test procedures for
testing with the flight UVIS detector during the upcoming
"mini-ambient" calibration.
Minor glitches found in data processing and CASTLE operations are being
worked.
*
Bushouse has
delivered version 0.2 of CALWF3 to OPUS/DST for installation in the OPUS test
environment.
*
S. Baggett has
verified and slightly improved the D2 lamp countrate estimates.
*
Our preliminary
conclusions, however, remain the same: based on the calsystem component
throughputs from the Ball SER (060), the detector QE curves from DCL, and the
new lamp spectra measured at GSFC, the five new D2 lamps should meet CEI spec
in all applicable filters.
*
MacKenty
presented at and the team supported the HST/442 MSR last week.
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TELESCOPES Branch
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Selected Highlights
*
A.
Sivaramakrishnan and R. Makidon participated in the Quarterly meeting of the
JWST Wavefront Sensing Working Group in Boulder, October 7-8. Sivaramakrishnan presented an overview of
the main options for the coarse phasing procedure that will cophase the
segments of the primary during the initial commissioning period. Two main options exist: Dispersed Fringe
Sensing, which requires individual segments to be physically moved out of
alignment in order that segments be cophased in pairs, and Dispersed Hartmann
Sensing, which uses pupil masks to generate pairwise interference
patterns. The two methods have
different hardware and operational impacts.
A detailed study will be carried out to determine the requirements and
risks associated with each method.
*
B. Saif
presented his technique based on instantaneous phase shifted interferometry for
high-precision measurement of distortions in large optical structures at the
meeting of the Optical Society of America in Tucson, October 6-9. He also carried out another laboratory
experiment in order to verify the measurability of structures with
thickness. Based on his work, GSFC
plans to procure an interferometer capable of carrying out measurements and
tests in house.
*
L. Petro
started the activity of the working group that will define the next iteration
of the Design Reference Mission, which will include a full representation of
onboard activities.
*
Petro reviewed
the sensitivity calculations for MIRI in the JWST Mission Simulator, and found
good agreement with the MIRI team for most calculations. As a result, MIRI will be included in the
next release of the JWST Mission Simulator.
*
J. Krist
measured the HST focus position both from dedicated observations and from a
selection of images taken for the Ultra-Deep Field. Unlike last month's measurement, all data indicate that the HST
focus is nominal, with measurements ranging from -2um to +3um.
*
O. Lupie and C.
Cox started developing a proposal for a uniform, consistent handling of the
geometric distortion and related work, for WFC3, using the experience with ACS
as a guide. Lupie also worked on
various aspects of WFC3 orientation and subarray geometries in preparation for
ground testing with flight hardware and flight detectors.
*
C. Cox
converted the geometric solution obtained by Jay Anderson for WFPC2 into the
standard form used in the Science Instrument Aperture File. Together with R. Hook, A. Koekemoer and
others, he supported the conversion of all WFPC2 geometric solutions to a form
consistent with the ACS IDCTAB structure, to facilitate the implementation of
improved geometric corrections for WFPC2 in DRIZZLE and related software.
*
E. Roberts
worked with Petro's group to incorporate the updated JWST design into the JWST
Mission Simulation software. He
obtained relevant temperature data from the Northrop Grumman finite elements
model of the telescope in order to obtain an improved estimate of the thermal
background due to the sunshield. He
also started an improved definition of the sunshield perimeter in order to
refine the light avoidance calculation and scheduling constraints within the
simulation software.
*
M. Miebach is
working with ESTEC personnel on the FOC Post Flight investigations.
*
T. Wheeler
investigated an anomaly in the WFC3 science data buffer management discovered
during the Phase VII Command Certification tests. Although he found the need for slight adjustments in TRANS
timing, this does not seem to be at the root of the anomaly.
*
E. Morse
started the development of a detector simulation package for use by NGST and
Ball in their image simulations aimed at determining the efficiency of
wavefront sensing activities. The
detector simulation is based on an earlier version written by Sivaramakrishnan
and Makidon, and includes realistic detector noise properties and readout sequences,
as well as cosmic rays.
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DA Branch
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SELECTED HIGHLIGHTS
* General
* Help desk statistics
* Appendix
DETAILED ACTIVITIES
General
* Data Analysts (DAs) in the branch, besides supporting INS instrument teams, also support other science and technical projects. 22 science and technical projects are currently supported by 20 DAs. 2 science projects are in the queue awaiting available resources. The wait time for the queue is approximately 2 months.
* Reports, publications, presentations and other achievements by members of the branch in September are listed in the appendix.
Help Desk Statistics
* The general/instrument help desk (help@stsci.edu) received 92 calls last month with the following distribution: 13 for General Help, 11 ACS, 1 FOS, 3 NICMOS, 9 STIS, 53 STSDAS and 2 WFPC2 calls.
APPENDIX A
Publications
Publications
Advanced Camera for Surveys Instrument Handbook for Cycle 13
Pavlovsky, C., et al.
http://www.stsci.edu/hst/acs/documents/handbooks/cycle13/cover.html