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. 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)

8. Latent Images Latents unlikely to be a big problem Data collected
Saturating flood illumination (~200k e-) in 4 frames
Latent strength, decay
100 seconds
<~ 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
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

11. 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 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
-- : 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)

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 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)

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