FOS
Post-Operational Archive
and
STIS
Calibration Enhancement
Michael R. Rosa
Space Telescope European Coordinating Facility
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POA/CE is an ESA task from MoU
• NASA/ESA MoU on HST
– in lieu of hardware contribution additional contributions by ESA
• Scope
– added science value of “pipeline calibrated” HST data
– homogeneous versions of calibrated data and documentation
– long term support to users world wide
• Implementation at ST-ECF
– since Oct 1999 - Instrument Physical Modeling Group (2.5 FTE)
– level of effort, in close consultation with STScI
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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Calibration Enhancement Strategy
• Obtain comprehensive view on entirety of data
– long term trends, cover environmental parameter range
– view data from different modes as coming from same genuine instrument
– empirical insight required to isolate effects while building physical models
• Employ physical models
– prescription primarily based on physical / engineering insight ( > 90 % )
– empirical “fudge” only as tolerable substitute ( < 10 % )
– sufficient predictive power for predictive calibration & forward analysis
• Link with operational pipeline - make public
– cross-fertilization, STScI pipeline is baseline and fall-back solution
– re-use existing software and environment (level-of-effort 2.5 FTE only !!)
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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Post Operational Archive FOS/BLUE
•
FOS was 1st trial instrument for POA concept
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Comprehensive review of 24,000 data sets (red + blue)
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Solutions for major calibration problems
had to descope to FOS/BLUE (essential telemetry not available to pipeline)
Wavelength zero points (X-Shifts up to 6 pix)
STPOA V1.0
Aug 00
+ new dispersion solutions, flatfields
STPOA V1.1
May 01
+ new scaling for darks, additional flats
STPOA V1.2
Aug 01 “final”
Patches and POA tools
STPOA V1.2.1 Nov 01
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S/W:
available from www.stecf.org/poa (also from STScI)
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Data:
from ST-ECF/CADC OTF system, STScI static archive
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General FOS User Support:
CalWorkshop 02
http://www.stecf.org/poa/
FOS & STIS Calibrations
M. Rosa
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POA FOS Blue X-Shift Correction
• Comparing results of ‘calfos’ with ‘poa_calfos’
• Parameters entering ‘poa_calfos’ correction:
– Orbital position and attitude (pointing) for geomagnetic model
– Setup of detector (Ybase, HV, X/Ypitch)
– Ambient temperature near Filter/Grating wheel
• Correction better 1 pix if data oversampled
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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Rapid Read sci case in ‘poa_calfos’
• Substantial improvement - typically ~ 200 km/sec
• Residual curvature
– a secondary effect of erroneous onboard GIMP correction
– can be removed by oversampling POA-CALFOS output
– not standard STScI philosophy, availabe as extra POA analysis tool
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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Dispersion Relations for POA-FOS
• Shown are residuals of calibration lines w.r.t. solution
• CAFOS - classical polynomial fit did all “good” lines “well”
– whether or not they are blends, wrong identifications, too sparsely spread
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POA-FOS Dispersion Model for all gratings
– mode specific parameters: grating constant, grating angle
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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MW Halo absorptions in QSO spectra
- Standard “calfos”
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2 long exposures (black,red) show repeat error in subsequent exposures
Unphysical dependency of velocity on wavelength
Only one absorption at 1403 A seems to fit expectation
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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MW Halo absorptions in QSO spectra
improved with “poa_calfos”
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POA GIMP correction minimizes repeat error from 2 long exposures (black, red)
All but one line match central value of expectation (21 cm line)
The one not fitting now is QSO Ly alpha redshifted (= NEW science)
Result of POA GIMP correction in combination with physical model dispersion
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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STIS - Calibration Enhancement
• Science value per effort
– Side 1 data (1997-2000) a well defined archive
– Spectrocopic data (2D, echelle) gain substantially from rigorous
application of geometric and environmental (thermal, orbital) models
• Synergies
– generic 2D spectrograph model: VLT/UVES ¤ HST/STIS
– orbital models (geomagnetic, thermal): HST/FOS ¤ HST/STIS
– modeling efforts for STIS at STScI, GSFC, ST-ECF, Ball (MSM,CTE)
• Benefits for operational pipeline (Side 2)
– gaining generic insight into STIS without impacting operational pipeline
– test new concept on archival data, not on life data stream
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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STIS Calibration Enhancement
• Physical model calibration approach
– Solid understandig of geometry paramount to understand trends, spectral
extraction and fluxing
– Isolate environmental impacts (thermal, attitude, particle ...)
– Improve spectral extraction & background estimation
– Carry over into new final flux-per-wavelength (and 2D) products
• STIS-CE corner stones - Timeline
– 2002/3 - Geometry & Wavecal physical model & improved NIST catalogue
– 2003/4 - Orbital, Trends, CTE mass analysis (65 000 data sets + pre-launch)
– 2004/5 - Extraction & Flux
packaging into CalibrationEnhanced pipeline
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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STIS Dispersion Model projected
onto E 140H short Auto-Wavecal
original (notice individual counts)
CalWorkshop 02
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smoothed (3*3 gauss)
FOS & STIS Calibrations
M. Rosa
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STIS-CE Status
• Critical review of documentation
(concluded Feb 02)
– entire STIS e-doc archive available (mirror from STScI)
– reviewed 268 ISR’s (GSFC and STScI), Handbooks, BALL-Reports
– basis to develop STIS-CE plan in consultation with STScI, STUC (ver Apr 02)
• Setup
– 5 TB of RAID required to manage the comnprehensive view on Side 1 (Jun 02)
– Special processing machine (SUN Fire 280R) for analysis, OTFC
(Jan 02)
– STIS generic 2D Echelle model implemented into IRAF environment (Jun 02)
• Interfacing with STScI
– visits on working level (typically 1 ST-ECF STIS-CE staff at STScI 2nd month
– regular updating / coordination: telecon/meeting at least quarterly
– longer term (several weeks) exchanges (P. Goodfrooij @ STECF Jul/Aug 02)
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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Two membres of the POA/CE team are present at 5
Q&A
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the Cal Workshop and will be happy to answer /
discuss
• Anastasia Alexov
• Paul Bristow
– see also his poster on STIS CCD CTE effects
CalWorkshop 02
FOS & STIS Calibrations
M. Rosa
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