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

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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

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Time (sec)A

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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

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Time (sec)

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Stripe 1 Stripe 2 Stripe3 Stripe4

C035 Top Ref pixels

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Time (Sec)

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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 QE@0.8um QE@2.0um 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