1 Wide Field Camera 3 TIPS 18 September 2014

2 WFC3 Inserted in SM4 (2009)

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4 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!

5 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  m 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

6 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  m to <1  m –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 –How to best exploit GAIA? All Guide Stars and many (most?) frames to <1mas absolute!

7 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

8 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

9 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

10 Departures Tomas Dahlen Mike Dulude  HLA Derek Hammer  Industry Bryan Hilbert  JWST Kai Noeske  MPIA Alex Viana  Industry

11 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

12 CSM Position and Blob Count

13 Reduction in CSM Moves

14 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

15 Sections From Two GRISM Observations (background level & structure varies)

16 He I 10830A Line

17 Background function of Day/Night Location with He Line

18 Minimal Effect without He Line

19 Spectroscopic Confirmation Dust particles on in-focus IR channel select mirror provide “negative” spectrum He I line present when background is high in both Grisms.

20 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

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