1 wide field camera 3 tips 18 september 2014. 2 wfc3 inserted in sm4 (2009)
TRANSCRIPT
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WFC3 Summary
• WFC3 is operating nominally
– Photometric zero points (including UV) stable to ~1% since 2009– Astrometric calibration is stable (dominated by HST OTA “breathing”)– UVIS CCD Detectors CTE declining as expected with radiation damage and
mitigation/correction methods have improved considerably– IR Detector shows essentially zero evolution of its performance in flight
– 5 year life requirement surpassed this summer!!• Kudos to GSFC, Ball Aerospace, e2v, Teledyne, etc…..
• Thanks to Kailash for helping with the refreshments this morning!
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Past Year Highlights
• Improved understanding of UVIS CTE and IR Persistence– Sink pixels in CCDs; GOs are 2/3 using Post-Flash in Cy22– IR Persistence depends upon many factors! Model available <5 days
• UVIS Initiative 2 Chip Photometric solution (this fall)– Includes improved UV flats; better darks
• IR Background variations He 1.0830 mm line; zodi– F105W and F110W: often can schedule around dusk/dawn– G102 and G141: two component background model
• Spatial Scan observations have “gone mainstream”– Exoplanets & Cepheid parallax distances (25 micro arc seconds)
• System improvements: CRDS, Side-Switch SMOV, QL• User Support: Contact Scientist identification of bad actors
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Future Initiatives (1)
• PSF Library– ~10^7 stars “reasonably isolated” with “reasonable S/N” in F606W– Will expand to entire set of WFC3 observations– First application: improve focus monitoring from ~2 mm to <1mm– Exploring methods for making this usefully available
• Astrometric improvements– Initial requirement: 4 mas (0.1 pixels) for AstroDrizzle– WFC3 very stable internally due to thermal control of optical bench– Inclusion of photolithographic mask offsets (2013) 2 mas– Inclusion of filter induced mid-spatial frequencies 1 mas
• Done for ~10 UVIS filters with sufficient Omega Cen data• Expanding to remaining filters over Cycles 22-23
– How to best exploit GAIA?• All Guide Stars and many (most?) frames to <1mas absolute!
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Future Initiatives (2)
• Better instrument calibration/understanding– Time correction for UVIS zero points (<0.3 percent per year)
• This affects visible (not UV or IR); WHY??– Continued exploration of infrared detector persistence
• Improved model for predicted images (but will hit limits)• Repeated observations of bright objects noise floor?
– Very high precision astrometric calibrations for spatial scans
• Advanced GRISM data reduction algorithms/software– Tools to handle observations at multiple roll angles– Modeling approach to extract fainter sources and understand errors– Highly synergistic with JWST and WFIRST-AFTA needs
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WFC3 Team (1)
• Jay Anderson – CTE Mitigation• Sylvia Baggett – Detectors Lead• Matthew Bourque – Detector Calibrations, PSF DB & QL• Ariel Bowers – Flats, WWW & QL S/W Lead• Gabe Brammer – IR Grisms and Backgrounds• Susana Deustua – Photometry Lead• Linda Dressel – User Support Lead & Image Analysis• Mike Dulude – IR Darks, Earth Flats, QL• Meredith Durbin – new RIA• Mike Fall – GAIA Astrometry• Kati Gosmeyer –Photometry & QL• Heather Gunning – Detector, CRDS & QL Ops Lead• Harish Khandrika – new RIA
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WFC3 Team (2)
• Knox Long – IR Detector Persistence• Jen Mack -- Flat Fields• Peter McCullough – Spatial Scans for Exoplanets & CSM• Kai Noeske – Photometry & CTE• Nor Pirzkal – IR Grisms and Backgrounds• Vera Platais -- Astrometry• Adam Riess – Spatial Scans for Astrometry/Precision Photometry• Elena Sabbi – Calibration Lead & Deputy Team Lead• Kailash Sahu – Photometry & PSF DB Lead• Dave Taylor -- Systems
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Departures
• Tomas Dahlen
• Mike Dulude HLA• Derek Hammer Industry• Bryan Hilbert JWST• Kai Noeske MPIA• Alex Viana Industry
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Engineering
• Analysis of Channel Select Mechanism– Two unexplained issues related to this critical mechanism
• Two episodes of particle contamination on CSM mirror (2009 and 2012)• Handful of mirror mis-positions (~0.3 to 0.5 motor steps; typical is <0.1
steps)– Coincidence?? Working hypothesis: failure of epoxy staking holding
pin in motor shaft– Response:
• reduce CSM usage via changes to ops rules and calibration program• tools for manage usage constructed• Careful monitoring
• Cause of small visible CCD throughput decline – new study
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Infrared Background Variation
• A major strength of the WFC3/IR channel is that Broad Filters and GRISMS are intended to be Zodiacal background limited
• Nominal Backgrounds: 0.5 to 1.0 e-/s/pixel• HOWEVER: sometimes brighter (up to 3 to 5e-/s) and non-uniform
backgrounds are observed• Particularly problematic for deep Grism surveys
• Causes now well understood• Pointing traversing central part of zodiacal cloud
• i<80°sun angle near ecliptic plane• Long dwells near bright earth limb (i.e. CVZ or near CVZ situations).• Inclusion of He I 10830Å line within the passbands of G102,
G141, F105W, F110W• Careful scheduling required for faint observations –
consult STScI
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Spectroscopic Confirmation
• Dust particles on in-focus IR channel select mirror provide “negative” spectrum
• He I 10830 line present when background is high in both Grisms.
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Invitation to Publish
• New SPIE Journal• Mark Clampin, Editor-
in-Chief• JATIS publishes peer-reviewed
papers reporting on original research in the development, testing, and application of telescopes, instrumentation, techniques, and systems for ground- and space-based astronomy.
• JWM is Associate-Editor covering space instruments