May 22, 2003WFC3 Report at the June 03 TIPS1 Optical alignment and image quality testing at GSFC Test lead: Bill Eichorn, GSFC Test conductors: George Hartig, Sylvia Baggett, Massimo Stiavelli Full suite of alignment and image quality tests performed twice: before and after vibe test. 1 st epoch : 21 Mar-18 Apr ’03, 2 nd epoch ongoing –WFC3 with non-flight detectors (IR MUX, UVIS surrogate) and flight POM installed in RIAF with OS (CASTLE) providing OTA- like point source illumination at 633 nm (only) –During 2 nd epoch flat fields in F336W, F439W, and F625W were also obtained –Over ~4000 images obtained on both IR and UVIS channels

May 22, 2003WFC3 Report at the June 03 TIPS2 Optical alignment and image quality testing at GSFC Test objectives: –Demonstrate Optical Stimulus (CASTLE) performance over field; develop techniques and procedures –Obtain pre-vibration (of OA) alignment baseline and compare it with post-vibration data –Compare with results obtained at Ball with Mini-Stimulus –Measure residual surrogate detector alignment offsets for use in flight detector alignment –Assess image quality and wavefront performance of the completed optical assembly

May 22, 2003WFC3 Report at the June 03 TIPS3 Optical Stimulus (CASTLE) Bld 29 Clean room Rm 150

May 22, 2003WFC3 Report at the June 03 TIPS4 CASTLE Schematic oders M3SteeringMirror PrecisionEncoders SwitchingMirror Slidesinplanefor ExtendedSources FiberFeed Integrating Sphere FluxMonitors Alignment Monitor Inverted Cassegrain with 46% Central Obscuration Images positioned over field with 2 gimballed flats - produces pupil rotation Point source XYZ stage permits accurate focus adjustment

May 22, 2003WFC3 Report at the June 03 TIPS5 CASTLE/RIAF in SSDIF

May 22, 2003WFC3 Report at the June 03 TIPS6 CASTLE Test Image Field Locations Measurements made at points, uniformly-distributed over IR and UVIS fields (4-5 used at Ball)

May 22, 2003WFC3 Report at the June 03 TIPS7 IR MUX Image at Field Center

May 22, 2003WFC3 Report at the June 03 TIPS8 UVIS Image Near Field Center

May 22, 2003WFC3 Report at the June 03 TIPS9 UVIS alignment focus scans with WFC3 corrector and CASTLE

May 22, 2003WFC3 Report at the June 03 TIPS10 IR channel focus scans feasible with CASTLE only

May 22, 2003WFC3 Report at the June 03 TIPS11 Phase Retrieval Phase retrieval (PR) analysis measures low-order aberration content of the system at the detector, including focus Sets of monochromatic images obtained at multiple focus settings, on both sides of best focus, and fit simultaneously to remove ambiguity IDL PR routines developed by Burrows & Krist (ca 1990), used for COSTAR, STIS, NICMOS, and ACS optical verification and alignment, and adapted for WFC3 Only 13 lowest-order terms in Zernike expansion used for wavefront fit; generally provides good indicator of alignment state and final optical performance

May 22, 2003WFC3 Report at the June 03 TIPS12 IR Channel Alignment Phase Retrieval Pupil/WFE map (cold mask) Measured MUX image Modeled (fit) image Weighted difference image

May 22, 2003WFC3 Report at the June 03 TIPS13 UVIS Channel Alignment Phase Retrieval Pupil/WFE map (OS obsc/spiders) Measured MUX image Modeled (fit) image Weighted difference image

May 22, 2003WFC3 Report at the June 03 TIPS14 Optical alignment summary Phase retrieval and focus scan (CASTLE fiber or WFC3 corrector) techniques yield similar, repeatable results Residual detector tip/tilt after alignment at Ball corroborated with CASTLE measurements using alternative focal surface alignment technique –Alignment of both detectors should be improved with shim offsets as flight detectors are aligned in transfer fixture at Ball UVIS detector roll off nominal by 0.8 degrees, position off by ~50 pixels –Set incorrectly at Ball, will be compensated for flight detectors IR detector roll nearly perfect (<0.1 degrees from nominal) IR focus is essentially identical to measurement at Ball UVIS focus differs by ~0.5 mm (STOPT) from Ball measurement –Believed to be due to offset in model positions for Mini-stimulus Vibration testing did not alter alignment or image quality apart from a small shift – identical in both channel – probably due to latches tolerance

May 22, 2003WFC3 Report at the June 03 TIPS15 UVIS Encircled Energy Measurements vs. Model CASTLE EE measurements require correction for 0.46 central obscuration ratio (OTA is 0.33), spider width and other differences from OTA, as well as limited measurement radius, to predict on-orbit EE performance. CEI Spec: EE(.25 arcsec diam.) > 0.75 (goal 0.80) at 633 nm EE spec will readily met, goal will likely be achieved on- orbit, if flight detector performance and alignment are as expected.

May 22, 2003WFC3 Report at the June 03 TIPS16 Flat Field Analysis C-D amp

May 22, 2003WFC3 Report at the June 03 TIPS17 Flat Field Analysis Many negative pupil images seen in the flat fields. They do not depend on the filter and have sizes compatible with what would be espected from dust particles on the surrogate UVIS detector. Vignetting has been found on one corner of the field of view. It is a triangular area about 400 pixels long and 30 pixels wide at the largest point. Over this area the flux rolls down by more than a factor 2. –Not caused by filters, pickoff or channel select mechanism: too sharp (pickoff) and unaffected by rotating filters/CSM to off- nominal positions –It may be caused either by baffles close to the detector or by the camera head itself (currently at an incorrect position)

May 22, 2003WFC3 Report at the June 03 TIPS18 Flat Field Analysis A-B Amp

May 22, 2003WFC3 Report at the June 03 TIPS19 Conclusions The various sets of measurements are consistent The data will allow us to position the flight detectors at the correct position Vibration testing did not significantly alter alignment or image quality Small amount of vignetting in UVIS channel (still to be investigated) EE field center goal on UVIS should be met over the whole field