TIPS May 22, 20081H. Bushouse

TIPS May 22, 20082H. Bushouse TV3 Science Team Cast of “Characters” Instrument Scientists: –Sylvia Baggett –Howard Bond –Tom Brown –Howard Bushouse –Susana Deustua –Linda Dressel –George Hartig –Bob Hill (GSFC) –Randy Kimble (GSFC) –John MacKenty –Andre ’ Martel –Peter McCullough –Larry Petro –Steven Rinehart (GSFC) QuickLook Operators: –Elizabeth Barker –Misty Cracraft –Bryan Hilbert –Sherrie Holfeltz –Diane Karakla –Jessica Kim –Kevin Lindsay –Doug Long –Ray Lucas –Jennifer Mack –Helen McLaughlin –Cheryl Pavlovsky –Brittany Shaw –Ed Smith –Megan Sosey –Alex Viana WFC3 Operations: –Tom Wheeler

TIPS May 22, 20083H. Bushouse High-Level Statistics Total of 743 hours (31 days) on Science Calibration activities –Initial ambient calibrations: Feb. 20 – 29 –Vacuum calibrations: Mar. 4 – Apr. 16 –Final ambient calibrations: Apr. 18 – hours (8 days) spent on unplanned investigations –UVIS window droplets –IR FPA persistence –IR bias jumps (“banding”) –UVIS PSF short-term stability (shutter-induced jitter) –UVIS electronic crosstalk linearity 555 hours (23 days) spent on original 20-day Science Calibration plan activities (15% overrun) ~ 265 SMS runs; 10,605 exposures; ~25 lbs of M&M’s

TIPS May 22, 20084H. Bushouse Objectives Met Calibrate all WFC3 science modes Obtain all data necessary to support on-orbit science operations and data calibration using UVIS-1’ and IR-4 detectors UVIS & IR detector calibrations: bias, dark, flat field, read noise, gain, linearity, full-well, fringing, … System-level calibrations: system, filter, & grism throughputs Verify system-level performance Optical alignment, image quality, photometric stability, scattered light, internal cal system performance Effects of input voltage and thermal cycling on calibrations Verify instrument performance model (Exposure Time Calculators) CEI spec and lien verifications, where possible

TIPS May 22, 20085H. Bushouse Accomplishments All tests in original 20-day calibration plan accomplished No tests or calibrations deferred to SMOV

TIPS May 22, 20086H. Bushouse Sci Cal Tests Completed Servicing Mission Aliveness/Functional Test UVIS & IR Optical Alignment UVIS & IR Science Monitors IR Darks (read noise) IR Background Levels vs. Filter IR FPA Gain IR FPA Linearity (full-well) IR Optical Performance (Encircled Energy) IR Throughput IR Filter Blue Leaks IR External & Internal Flat Fields IR Flat Field Stability IR Grism Narrowband Flat Fields IR Grism Flux Calibration (throughput) IR Grism Dispersion & Spectral Trace IR FPA Edge and Baffle Scattered Light IR Photometric Stability IR Electronic Crosstalk IR Bias/Dark vs. Orbit Cycling IR Rate Dependent QE IR Intrapixel Sensitivity IR Persistence UVIS Bias (read noise) UVIS Darks UVIS CCD Gain UVIS Linearity (full-well) UVIS Optical Performance (Encircled Energy) UVIS System Throughput UVIS Filter Throughput UVIS CCD Red Cutoff UVIS Filter Red Leaks UVIS External & Internal Flat Fields

TIPS May 22, 20087H. Bushouse Sci Cal Tests Completed (2) UVIS Flat Field Stability UVIS Grism Narrowband Flat Fields UVIS Grism Flux Calibration (throughput) UVIS Grism Dispersion & Spectral Trace UVIS CCD Fringing UVIS Glint UVIS Electronic Crosstalk UVIS Filter Wedge UVIS CTE EPER Flat Fields Unplanned tests: IR Bias Jump Monitor UVIS Window Droplet Investigations UVIS PSF Stability (shutter-induced jitter) UV Quantum Yield Measurements UVIS CCD Amplifier “smearing” check

TIPS May 22, 20088H. Bushouse UVIS CCD Characteristics Read noise: 3.0–3.3 e - rms Dark current: <1 e - /pix/hour Full-well: 70-85k e - All consistent with TV1 results using detector with same CCD chips

TIPS May 22, 20089H. Bushouse UVIS Flat Fields F275W F555W F814W 15% structure 7% structure 59 of 66 filters have total of 120ke - in flats (0.3%) 7 (all narrow quads) have 40-80ke - ( %)

TIPS May 22, H. Bushouse IR FPA Characteristics Read noise in a CDS difference image: ~22 e - /pix rms –Averages down to ~14 e - over 16 samples Dark current: ~0.05 e - /pix/sec Linearity: 5% at ~72k e - –Hard saturation at ~84k e -

TIPS May 22, H. Bushouse IR Flat Fields “Death Star” “Wagon Wheel” 35-40% structure >200k e - in all IR flats (~0.2%)

TIPS May 22, H. Bushouse Orbital Cycling Vary thermal environment and WFC3 input voltage to simulate orbital cycles Check IR FPA temperature and bias stability Temp stable to ~0.6 K

TIPS May 22, H. Bushouse Open Issues/Studies UVIS “bowtie” feature UVIS shutter-induced image jitter IR image persistence Launch on Side 1 or 2? –Intermittent IR bias jumps seen on Side 1 –UVIS shutter jitter somewhat worse on Side 2

TIPS May 22, H. Bushouse UVIS “Bowtie” Regions of enhanced brightness occasionally seen in darks and flats Example here is at strongest level yet seen (5% UV flatfield enhancement in the bowtie and in the location of two alignment spots) Typical levels are much less (0.5-1%)

TIPS May 22, H. Bushouse Bowtie Investigation Physical mechanism not understood; there appears to be both a persistence and a QE hysteresis phenomenon at work Physical morphology is suggestive of a charging effect (electrical field “pincushion” morphology) The DCL has never seen this behavior in testing of e2v devices, yet it has been seen with UVIS-1, UVIS-2, and UVIS-1’ in WFC3 Science team is surveying all biases, darks, and flats from T/V-1, TV-2, and TV-3 to identify all examples and search for trends, correlations Seems to occur most often in images taken in ambient (CCD’s warmer than flight), or soon after detector cooldown, but not always The clear CCD-level symmetry naturally suggests a CCD-level cause – no upstream sources (optics, stray light, CASTLE illumination) know anything about the split focal plane The problem does not arise in the readout electronics (not present in the overscan; readout wouldn’t know about alignment spots)

TIPS May 22, H. Bushouse UVIS Shutter-Induced Image Jitter Series of short (1 sec) exposures shows lower peak pixel fraction and larger PSF width in alternating images, while total flux is constant Phase of alternating behavior correlates with phase of the 2-blade shutter mechanism For exposures >5-10s, no significant effects are seen

TIPS May 22, H. Bushouse Effects Are Strongest In Short Exposures and Small Apertures Theory: motion of shutter induces mechanical jitter in the instrument that slightly blurs short exposures; the element most likely affected is the UVM1 mirror (<1 arcsec of rotation of that optic is required to produce the effects observed) Possible changes to shutter operations (starting position, encoder feedback, etc) under investigation EE (diameter in arcsec)

TIPS May 22, H. Bushouse IR Image Persistence Initial test using 0.5x-100x full-well sources showed negative persistence (essentially negative dark current); never seen in DCL tests Severe over-illumination had occurred due to ground test equipment Reran with modified techniques, which showed normal positive persistence, and was (as expected) very low for the sub-full-well exposures Target brightness constraint for IR channel could result, though the strong preference is to avoid this; perhaps at least an alert to observers as to the potential effects of very bright objects in their target fields

TIPS May 22, H. Bushouse IR Bias Jumps: Gone but not forgotten Low-level bias shift (~2.5DN) was seen intermittently only in lower left quadrant of readout; effect is tracked by the reference pixels in those rows Only seen with Side 1 electronics Initial rate of occurrence: ~4.5% of all reads After March 19: zero in >3000 reads

TIPS May 22, H. Bushouse Results & Remaining Work ISR “IR Channel Blue Leaks”, T. Brown ISR “IR Channel Baffle Scatter”, T. Brown ISR “UVIS Channel Glints”, T. Brown ISR “UVIS Filtered Throughput”, T. Brown ISR “IR Channel Throughput”, T. Brown  Finish TV3 analysis and delivery of calibration reference files by end of July