NIRCam DHAS and Array Characterization John Stansberry UofA NIRCam team
Jan 02, 2016
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)
1. Reference pixel subtraction
2. Dark (ramp?) subtraction (don’t have satisfactory cal frame yet)
3. “CR” detection/removal
4. Linearity correction, saturation detection
5. Slope & intercept determination Ramp fitting Slope from frame0
6. Flat-fielding
7. 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 rampsTo 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”
• 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 image patternHigh dark-current pattern
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
C042 32K Latent
-5.000
0.000
5.000
10.000
15.000
20.000
25.000
30.000
0 2 4 6 8 10
Ramp No.
AD
Us
Run 1 Run 2 Run 3 Run 4 Run 5 0.05 Percent
200sec data ramps
0.05% level
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
Run 11 Linearity
0
10000
20000
30000
40000
50000
60000
0 100 200 300 400 500
Time (sec)A
DU
s -
C042 Patch C042 Patch Lin Fit
C042 Patch 2nd O Fit C042 patch High linearity
Popcorn / Random Telegraph Noise
• 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
Single event per ramp Multiple Events
0.29% 0.095% 1.2% .002%
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
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…
C035 Active Pixels
0
10000
20000
30000
40000
50000
60000
0 50 100 150 200 250
Time (sec)
AD
Us -
Stripe 1 Stripe 2 Stripe3 Stripe4
C035 Top Ref pixels
5000
5500
6000
6500
7000
7500
8000
0 50 100 150 200 250
Time (Sec)
AD
Us
-
R2045 S1 R2045 S2 R0245 S3 R2045 S4
R2046 S1 R2046 S2 R2046 S3 R2046 S4
R2047 S1 R2047 S2 R2047 S3 R2047 S4
R2048 S1 R2048 S2 R2048 S3 R2048 S4
Backup
Summary of Flight Candidate Properties
SCA Dark
Current Read NoiseCDS Read
Noise [email protected] [email protected] Operabilitye/sec e e
Req 0.01 9 21 0.7 0.8 0.96FM FPA #1 C038 0.001 8.3 18.3 0.69 0.99 0.99
C073 0.001 6.7 13.7 N/A 0.98 0.99C043 <0.001 6.5 17.0 0.83 0.99 0.99C045 <0.001 7.4 20.1 0.90 0.84 0.99
FM FPA#2 C044 0.0001 7.5 18.8 0.91 0.91 0.99C063 <0.001 7.6** 16.7** 0.69 0.96 0.985C072 0.01* 6.9 17.8 N/A 0.8 0.988C074 0.01* 8.2 16.3 N/A 0.81 0.986
Spare C049 <0.001 7.0 18.6 0.87 1.00 0.95C064 <0.001 7.3** 16.5** 0.75 0.92 0.986C067 0.001 7.2 19.4 N/A 0.91 0.98C041 <0.001 7.9 15.3 0.49 0.79 0.98
**Based on Az analysis of TIS data
-- : 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
C073 C038
C043 C045
Note that SCAs can only be positioned with their connectors along the top or bottom edges of the FPA.
Illuminated Dark
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.
On the way to San Jose (eg. Vibe)
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.
Flight FPA #2 Candidate Arrangement
C063 C074
C044 C072
Illuminated Dark