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; …) 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?

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

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

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

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

Dark Current “Settling” Latent image pattern High dark-current pattern 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)

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

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

Popcorn / Random Telegraph Noise Single event per ramp Multiple Events 0.29% 0.095% 1.2% .002% 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

First-Frame Effect NIRCam only issue (?) Fitted function Reference level (from top RP’s) 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

Correction of First-Frame Effect

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…

Backup

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

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

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

Qualification SW FPA        In the clean room handling jig. In the metrology dewar. 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)

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