WISE Flight System Idiosyncracies Relevant to Data Processing Frank Masci, v. 2.1, 01/01/2010 Both pre-flight expectations from ground characterization, speculations, and post-flight findings are listed below. There is a code at the end of each item to indicate its origin: [P] = pre-flight finding or expectation [F] = confirmed post-flight or new finding [S] = pure speculation or unknown [P,F] = both [P] and [F] above A pictorial gallery of detector idiosyncrasies is posted here. This document is organized as follows: A. Detector/Electronic Properties B. Image/Optical-System Properties C. Spacecraft Maneuver/PCS Features A. Detector/Electronic Properties --------------------------------- (1) Detector Bad Pixels - W1/2 bad pixels evolve with thermal cycles [P,F] - bad-pixel transients in general: timescales, stability? [P] - popcorn noise? [P] - Build up of low/high response pixels in W3/4 as a result of radiation damage (e.g., SAA passages) [S] (2) Detector (fixed frequency / variable phase) pattern noise - all bands: - Odd/Even column (amplifier-dependent) patterns in W1/2? [P,F] - Corrugation patterns? [P,F] (3) Si:As Detector Banding - DC level shifts in rows/cols at hot pixels in W3, W4 (banding) [P,F] (4) Detector Linearity - surprisingly large [P] (5) Latents: - Suppression following anneals [P,F] - Parent source color dependence? [S] - Parent source flux dependence, including saturation? [P,F] - Cosmic ray latents - yes: IOC analysis => saturated cores of CR hits give latents in subsequent frame only [F] (6) Post anneal behavior: - exponential decay of response proportional to temperature decay and stabilizing after about 15 minutes? [P] - drifts in response as temperature settles over about 3 hours [P] - unexplained upward response drift in W3 (2% in 2 hours) in one MIC-2 test? [P] - Dark/Response settling [S] - temperature equilibration following anneals [P,F] (7) W3/4 droop: - dependence on amplifier quadrant? [P,F] - dependence with "bad-pixel banding" region [P,F] - non-saturating and/or just saturating signals? [P] - gain or offset effect? [S] (8) Saturation induced idiosyncrasies: - dark rings and their decay (all bands), quadrant dependence? [P] - column pulldown [S] - muxbleed [S] (9) Output channel temporal variations/noise: - e.g., ch.14 in w1 L0's; ch.15 in w2 L0's following IOC dark and read-noise analysis [P,F] (10) High energy cosmic rays appearing extended and source-like - secondary showers [F] - frequency of occurence? [S] - impact on single frame source extraction? [S] B. Image/Optical-System Properties ---------------------------------- (1) Discrepancy between predicted and measured RSR [S] (2) PSF focal-plane position dependence due to - FOV distortion [P,F] - aberrations [S] - scan mirror non-linearity [S] (3) Ghosting - in W3/4 seen in MIC2 and flight data [P,F] (4) stray light (as seen in MIC2 droop test) [P,F?] (5) glints [F] (5) Source halos from internal self-reflections? [S] (6) W3/4 measles, in MIC2 only? [P,F] (7) Dust specs on any optical elements, including scan mirror? [S] (8) Low-frequency responsivity variations, throughput stability? [S] Spacecraft Maneuver/PCS Features -------------------------------- (1) Spacecraft drifts during scans and frame exposures: - impacts on image quality, PSF? [S] (2) Spacecraft drift/settling following maneuvers, and mid-scan [P,F]