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NIRCam DHAS and Array Characterization

NIRCam DHAS and Array Characterization. John Stansberry UofA NIRCam team. Pipeline/DHAS Implementation. NCDHAS Written in C++ for speed (fitsio libraries required) 80 MB per frame/group if running all 10 arrays FITS extensions (slope & uncertainty; intercept & uncertainty; …)

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NIRCam DHAS and Array Characterization

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  1. NIRCam DHAS and Array Characterization John Stansberry UofA NIRCam team

  2. Pipeline/DHAS Implementation • NCDHAS • Written in C++ for speed (fitsio libraries required) • 80 MB per frame/group if running all 10 arrays • FITS extensions (slope & uncertainty; intercept & uncertainty; …) • Modular design (implemented modules) • Reference pixel subtraction • Dark (ramp?) subtraction (don’t have satisfactory cal frame yet) • “CR” detection/removal • Linearity correction, saturation detection • Slope & intercept determination • Ramp fitting • Slope from frame0 • Flat-fielding • IPC/Hysteresis? At what stage in this flow?

  3. Other Data Processing and Analysis Tools • FITS packer for Teledyne data (UA data OK as is) • All frames/groups placed into a data cube • Much simpler directory structure, I/O • Data organization vastly simpler with this format • Data Visualization • IDL GUI (ncview) based on ATV • Pan, zoom, scale • Pixel/region values, slope or DN images, ramps/fits • Currently limited to single-SCA support • Accumulator • Converts “raw” data to flight-like multiaccum/grouped data

  4. NCView Latent-decay exposure Functionality: DN images; Pixel ramps To Do: other images, region statistics,…

  5. Array Characterization at UofA • UofA array testing facilities • Leach controller (4 SCAs 25-frame exposures; 1 SCA 90-frames) • Linux workstation, scripting capability, telemetry logging • Luppino dewar, 1-4 SCAs or SW FPA, LED sources (diffuse) • Performance/Sensitivity • Readnoise, dark-current, QE, gain, operability from Teledyne • All but QE confirmed post-delivery at UofA • “Features” • Dark-current settling (problem resolved) • Latent images • Nonlinear response • Cosmic-ray like: RTN / popcorn; snowballs • 1st Frame effect • Reference pixel ramps

  6. Dark Current “Settling” • Early dark measurements at UofA were not very stable • Decreasing dark current vs. time • Spatial pattern of dark also time dependent

  7. Latent image pattern High dark-current pattern Dark Current “Settling” • Effect may be due to incorrect array voltages after data collection system crashes • As if the arrays were flooded with charge • Decay time-constant much longer than for latent images, though. • Also mitigated by double-resets, and adequate settling time after system is brought up • Unlikely to be an issue when running w/ ASICs (to be confirmed soon)

  8. Latent Images • Latents unlikely to be a big problem • Data collected • Saturating flood illumination (~200k e-) in 4 frames • Latent strength, decay • <0.05% @ 100 seconds • <~ 0.5% @ 10 seconds • To Do • Range of brightnesses, temperatures • Higher time resolution to measure the decay 0.05% level 200sec data ramps

  9. Nonlinear Response • Ramps are nonlinear • ~10% effect near saturation • Correction strategy • Extensive data sets being collected • 2nd O polynomial works well • Correction verification may only be possible on-orbit • Calibration observations over wide range of source brightness • No absolutely calibrated sources available for I&T

  10. Popcorn / Random Telegraph Noise Single event per ramp Multiple Events 1.2% 0.095% .002% 0.29% • 63 900sec dark exposures, 10.6sec sample time, part C048 • <1% of pixels show event in a 1000 second ramp • Location of single events depends strongly on output amp. • Few 100 DN amplitude

  11. Fitted function Reference level (from top RP’s) First-Frame Effect • NIRCam only issue (?) • Elevated DN in 1st frame after reset • Decays w/  ~ 30usec • Affects ~20 detector rows @ edge w/ outputs • RPs and active pixels • Dark-like correction • Impact on grouped data • Group-1 includes 1st frame • NIRCam also gets 1st frame separately

  12. Correction of First-Frame Effect

  13. Reference Pixel Ramps • Reference Pixels “integrate” • Darks: RP’s show no measurable slope • Strong illumination: RP’s show distinct slopes • Appears to be coupling in the multiplexer • Do the active pixels also show this effect? Testing…

  14. Backup

  15. Summary of Flight Candidate Properties : Formally misses SCA-level req but top-level sensitivity spec not violated (assuming no other problems) -- : data not yet received from TIS N/A : removed short wavelength tests

  16. Flight FPA #1 Candidate Arrangement Illuminated Dark Note that SCAs can only be positioned with their connectors along the top or bottom edges of the FPA. C073 C038 C043 C045

  17. Dark Current “Settling” High dark current condition Low dark current condition

  18. Qualification SW FPA    In the metrology dewar. In the clean room handling jig. In the GL performance dewar. Metrology and performance measurements have been repeated post-vibe: No changes were seen relative to pre-vibe! Qual FPA has been taken to LM ATC for use in FPE check out (w/ ASICs).     After FPE check out, the qual FPA will return to Arizona for use if anomalies or detector issues need investigation. On the way to San Jose (eg. Vibe)

  19. Flight FPA #2 Candidate Arrangement Illuminated Dark C063 C074 C044 C072

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