March 18, 2004Tips – Olivia Lupie1 WFC3 Filter Testing, Modeling, Designing Ghosts (spurious reflections) in some UVIS filters were discovered during first ambient calibration of WFC3 Ambient Cal Filter Ghost Characterization – T. Brown, O. Lupie GSFC Lab Setup (spare and proto-type filters): Randy Telfer (Orbital, GSFC), Ray Boucarut (GSFC) Filter Modeling: Dave Kubalak, Randy Telfer, (Orbital), Bill Eichhorn (GSFC) GSFC Lab Data Reduction, Analysis: Sylvia Baggett, Olivia Lupie Vendors: Barr Associates, Omega Optical UVIS Ambient Nano Calibration – G. Hartig, N. Reid, S. Baggett, T. Brown, H. Bushouse, B. Hilbert, O. Lupie TEAM

March 18, 2004Tips – Olivia Lupie2 Parameters Used to Spec a Filter to Vendors Vendor uses specs to design a filter: Determine substrates, coatings, coating thicknesses, deposition process. Provide model of throughput, out of band rejection, spatial uniformity Model is accepted or rejected Vendor builds the filter

March 18, 2004Tips – Olivia Lupie mm    UVIS CCD Filter Wheel Edge Rays Define Field-Of-View Image Image Rays Instantaneous Beam Footprint 14 mm10 mm ~3 o WFPC-1’s SOFA – 12 wheels Converging instantaneous beam footprint F31 beam +/- 3 degree range for field angles WFC3 Filter Testing, Modeling, Designing

March 18, 2004Tips – Olivia Lupie4

March 18, 2004Tips – Olivia Lupie5 Spectral Shaping of the Filter

March 18, 2004Tips – Olivia Lupie6 Modeling Status Anti-reflection Shortpass 1 Substrate #1 Metal blocker (aberrations – astigmatism) Substrate #2 Shortpass 2 Transmitted 1 st order ghosts aberrated 2 nd order ghosts doubly aberrated Possible Model of F225W Ghosting (modelers: Randy Telfer, Dave Kubalak) Aberrations result from reflections from metal blocker Substrate 1.1 mm GAP (0.38 mm) Substrate 3.0 mm Bond & Spacer Air-Gap Construction Ideally – all surfaces perfectly parallel Airgap replaced adhesive – adhesive reduced throughput and introduce major spatial dependence across filter

March 18, 2004Tips – Olivia Lupie7 F218W F225W F300X F606X <1% in white light > 10% in white light (analysis T. Brown with ICAL team) Flight Filter Ghosts (worst cases) Some wide band UV air-gap filters exhibited large amplitude ghost images:

March 18, 2004Tips – Olivia Lupie8 Faint point ghosts at ~0.1% of the primary image intensity, moving little with field position. Larger donut ghosts at 0.3%, moving significantly. 0.02% 0.3% 0.06% 0.08% 0.13 % 0.08% test artifact Flight – F606W in WFC3 White light – 5 micron fiber Faint point ghosts at ~0.01% of the primary image Intensity. Field angle check in work.. *white light ghosts 10x fainter than Flight – however more testing is needed to verify. Spare – F606W – lab Cohu, 10 micron fiber Xenon Lamp Lab Measurements of Spare F606

March 18, 2004Tips – Olivia Lupie9 200 nm 400 nm 275 nm 1100 nm F225W Primary imagesghosts Low level ghosts

March 18, 2004Tips – Olivia Lupie10 Spectral Modeling of Ghosts (D. Kubalak) Ghost spectral modeling- D. Kubalak

March 18, 2004Tips – Olivia Lupie11 Phase Retrieval and Spectral Ghost Models Flight Filter Flight Filter Phase Retrieval from Focus Sweeps (R. Telfer) Strange Morphology  combination of Astigmatism, overall curvature, local surface ripples

March 18, 2004Tips – Olivia Lupie12 Two-surface reflection modeling indicates the metal blocker is the likely origin of the ghost behavior. Vendors also say that the metal coating is the least “controllable”. The observed wavelength dependence is understood. Red and Blue near-band wings are not as steep as desired. This excess light occurs at the wavelengths where ghosts could be produced by the air- gap construction. Model ghost fluxes (10-12%) are comparable to measured in white light. Phase Retrieval reveals ghost images are astigmatic for 218W and 225W, that the coatings are tilted w/r to one another, and filter has a slow, slight curvature  possibly consistent with a shrinkage/distortion at the spacer/metal blocker interface. None of these issues have any effect on the transmitted beam and throughput – both were excellent. Air-Gap Ghost Mechanisms

March 18, 2004Tips – Olivia Lupie13 Status Filter-Ghost Mitigation Plan 1.Adopt a 3-option approach for Air-Gaps: Barr to proto-type new F218, 225, (and 300X) filters – single substrate IPT tested image quality using special lab setup – flight Spare filters to see if they exhibit less ghosting. IPT is investigating a wedge fix – original design but with increased wedge to deflect reflected light; IPT is investigating dual-wheel air gap – achieved wedge by stacked-SOFA wheel approach; requires two coated substrates and loss of a filter(s). 2. Mechanism for F606w (laminated) ghosts is being discussed with OMEGA. Barr sent thin prototype single substrate – testing in the GSFC – only one ghost present, white light 0.6% F218 and F225 spares  same problem. F606 spare exhibits similar type ghosts but greatly reduced ghost amplitude (~0.03%) Modeling shows you cannot tilt filter enough and still stay with bounds of the filter housing.. By “tilting” the spare air-gap, we can determine how much relative tilt of the two substrates is needed to move the ghosts out of the fov. Data taken last night. OMEGA is devising a new design. STATUS PLAN

March 18, 2004Tips – Olivia Lupie14 Off-axisParabola Filter CCD Fiber F/31Beam Castle Cart Double Mono chrometer UV Sensitive CCD. Cover Structure for uniform/dark background. Mechanical stage mount for filters. Automated Castle and CCD data take system. Semi-Automated data reduction and analysis. GSFC Lab Testing Facility Goals – last few weeks: 1) Prove that the GSFC Lab Test setup accurately simulates the WFC3, i.e., measurements are true representations of the filter imaging quality, and 2) Measure the flight spares. Optics Team: R. Telfer, R. Boucarut, D. Kubalak, B. Eichhorn, J. Kirk, B. Greeley Science IPT: O. Lupie, S. Baggett, B. Hilbert, T. Brown, G. Hartig presents F31 light beam to the filters as they would see in the WFC3+OTA

March 18, 2004Tips – Olivia Lupie15 SPARE F225 Cohu Video CCD, 200 micron fiber FLIGHT F225 5 micron fiber, WFC3 10% 0.5% Saturated prime 10% Saturated prime (sum ghosts=15%) UV00 UV14 Lab Measurements of Spare F225W Note – rotation and stretch are different. SPARE F225 SBIG CCD,10 micron fiber, UV00 UV14 Saturated prime 9% 2% 0.5% Relative positions and fluxes of ghosts in the spares are comparable to those in the flight  similar mechanisms.

March 18, 2004Tips – Olivia Lupie16 Example Monochromatic Results for Spare F225W 220nm Spare F225, SBIG-CCD, 200 micron fiber, 13nm bandpass, double UVIS,, with ND1 (removed in later imaging). 240nm 260nm 280nm 300 nm 320 nm 340 nm Figure from S.Baggett

March 18, 2004Tips – Olivia Lupie17 Ran many tests to establish sensitivity to ghosts, setup alignment accuracy, and experimented with several different filter orientations: rotation, back to front, tilts, translation, wedge orientation and detector tilts. nominal -1d +1d -2d +2d Establish Setup Sensitivity and Repeatability Rotate Filter a few degrees from nominal and compare Ghost morphology Xenon Lamp, 10 mic Fiber Spare F225W

March 18, 2004Tips – Olivia Lupie18 Primary, Secondary ghosts emerge from behind the primary and each other when large translations or rotations of the filter are introduced: ie different locations on filter and differing field angles. center +0.5 in -0.5 in +1.0 in -1.0 in v. Large tilt – 30 deg to corner saturatedunsaturated saturatedunsaturated center - shows repeatability Establish Setup Sensitivity and Repeatability Also Helps modelers to see all the ghosts Translating the filter Xenon Lamp, 10 mic Fiber Figure from S.Baggett

March 18, 2004Tips – Olivia Lupie19 Prototype F225 – Single Substrate Prototype Single Substrate – large tilts (Xenon Lamp, 10 micron fiber, CCD SBIG) nominal-3d -6d -9d -12d -15d Prototype thickness is smaller than that of a flight filter. Thicker filters result in ghosts at a larger radial distance from the primary. But tilting the thin filter, we can see when the ghost emerges and use a simple Model to derive the ghost position with a thicker filter. Setup artifact Ghost 0.6% Figure from S.Baggett

March 18, 2004Tips – Olivia Lupie20 Proto Type F225 From Barr

March 18, 2004Tips – Olivia Lupie21 Prototype F225 – Single Substrate Ghosts as a function of wavelength Setup SBIG CCD, 200 mic fiber Castle Modes <250nm double UV double UVIS double VIS >760 double IR Setup artifact Ghost#1 Ghost#2 200nm 225nm 250nm 300nm 350nm 400nm 450nm500nm 600nm 800nm 650nm 850nm 700nm 900nm 750nm 900nm Figure from S.Baggett

March 18, 2004Tips – Olivia Lupie22

March 18, 2004Tips – Olivia Lupie23 53 of 63 filters exhibit excellent performance, consistent with spec. 47 filters < 0.2% ghosts 6 filters % ghosts - multi-substrate - 410M, 689M, 814M - air-gap – 656N, 665N, 673N 2 filters 0.7% ghosts: single substrate+Al blocker - 275W  can calibrate air-gap - 658N 2 UV high priority air-gap ( with Aluminum blocker) 10-15% ghosts - 218W, 225W  unsuitable for flight 1 UV air-gap 1% with strange morphology - 300X  marginal, tough to calibrate 1 3-substr laminated, < 0.5% “point-like” ghosts - 606W  most used filter, concern (other filters with very low level “point ghosts”: 625W, 775W, 410M, 467M, 547M, 621M, 689M) 1 UV single subst.+Al block, possible surface flaw – 280N  serious but low priority filter 2 UV Quad filters single substrate, 5% ghosts:– 232N, 243N  low priority filters, can calibrate Grism – data reduction in work