NIRCam Status

1

• NIRCam Status
• Marcia Rieke
• University of Arizona
• JWST Partners Workshop
• Ottawa, Canada May 19, 2009

JWST-PRES-012902
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Read Noise with ASICs
A set consisted of 30 80-sample ramps. Data
taken using development unit ASICs and Qual FPA
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How to Use Subarrays

• An open question in using the subarray readout
  mode is whether special calibrations are needed
  for each subarray location and size or whether
  data can be extracted from full frame data.
• For 2-sample (CDS) data, we may recommend
  taking darks before the exposure
• SCAs run from an ASIC may not have the reset
  anomaly that we see running in buffered mode w/ a
  Leach controller
• Reference pixels do not provide any
  benefit.
• Again need to be careful about
  possible ASIC vs Leach or buffered
  vs unbuffered mode
  caveats
• Flats can be used from full frame data.

no ref pix corr ref pix corr
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Illuminated Subarrays
NIRCam will use a subarray or window readout
mode to extend dynamic range. It may be the
principal mode for observing transits by
extra-solar planets. A 128x128 subarray was used
with four SCAs (two shown here) in our test
dewar. Illumination was provided by 2micron LED,
and a series of 2-sample ramps were taken.
Arrays run simultaneously so LED variations are
seen in all.
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Subarray Flatfielding

• Gray scale and plot show the result of ratioing
  subarray to full frame data. Neither image was
  linearity-corrected. The variations of /-2
  agree with expectations from counting statistics.
  Full frame flats appear to be fine for use with
  subarrays.

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Flight Short Wavelength FPAs are in Assembly
FM1 Dark (black is good)
FM1 Illuminated (white is good)
Red box is coronagraphy field.
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FM2 Dark (black is good)
FM2 Illuminated (white is good)
Red box is coronagraphy field.
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Flight Wide Filters

• Plot below shows the transmission functions for
  the flight candidates. Dashed line is the
  requirement.
• Out of band blocking is also excellent.

Req.
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ETU Optic Test Pupil Wheel ConfigFWA ETU Optic
Test
PW9 WEAK LENS - 7
PW8 OUTWARD PINHOLES
PW10 Uncoated Fused Silica
PW7 FILTER SURROGATE
PW11 WEAK LENS - 6
PW6 DHS MASSSURROGATE
PW12 ETU DHS 2
PW5 FILTER SURROGATE
PW1 CIRCULAR APERTURE
PW4 FILTER SURROGATE
PW2 FLAT FIELD PINHOLES
PW3 Uncoated Fused Silica
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ETU Optic Test Filter Wheel ConfigFWA ETU Optic
Test
FW2 FILTER SURROGATE
FW1 FILTER SURROGATE
FW3 FILTER F115W
FW12 DHS FILTER F150W2
FW4 FILTER F070W
FW11 FILTERF070
FW5 FILTER F200W
FW10 FILTER SURROGATE
FW6 FILTER F212N
FW9 IMAGING PUPIL
FW7 WEAK LENS - 8
FW8 FILTER F187N
Optics used in acceptance test
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DHS Element in ETU Pupil Wheel
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ETU Pupil Imaging Lens Assembly

• Precision alignment and KOH bonding of ETU PIL
  optics is complete
• Assembly is being integrated with mechanism for
  further environmental tests

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ETU Short Wave Fold Mirror Assembly
WFE Pre-Vibe 11.4 nm rms
WFE Post-Vibe 11.8 nm rms
Vibration Configuration
SWFM Assembly
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ETU SWFM Cryo-cycling Results
Requirement 17.8 nm (CA)
Bottom of 3rd Cycle 13.8 nm rms

• Mirror exceeded spec in first Cycle, then
  maintained acceptable surface figure through
  Cycles 2 and 3
• Note chart shows only data points taken at
  points of thermal equilibrium

15
Progress on Wavefront Error
Recall that the NIRCam optical train as first
realized in the Pathfinder did not meet its
wavefront error requirement.
Several causes were identified 1)
Mount-induced distortion 2) Coating-induced
distortions 3) Poor alignment of lenses
within a triplet An improved alignment scheme is
helping, and the coating problem has been traced
to thermal shock at JDSU. A new bonded mount
design is the last improvement.
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Short Wave Bonded ZnSe Singlet
Optic Saver Standoff
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Surface figure cooldown of SW ZnSe S1
Surf fig rms 2.85nm
Zernike coeffs for surface S1 deformation (mm)
N M A(N,M) 0 0 -5.183155E-10 Piston 1
0 1.300426E-10 X-tilt 1 1 -1.121232E-09
Y-tilt 2 0 -5.291451E-09 Astigmatism -45
2 1 1.448882E-06 Focus shift 2 2
1.274113E-09 Astigmatism 0 or 90 3 0
-3.222958E-11 Trefoil Y 3 1 2.269643E-08
Coma 3rd ord Y 3 2 2.980256E-09 Coma 3rd
ord X 3 3 -8.016083E-06 Trefoil X 4 0
1.895118E-09 Tetrafoil Y 4 1 -7.188401E-10
4 2 2.088516E-07 Spherical 3rd Focus 4 3
2.122979E-09 4 4 -4.484867E-09 Tetrafoil X
5 0 -2.934174E-09 Pentafoil Y 5 1
-4.836911E-11 5 2 7.533641E-09 Coma 5th ord
Y 5 3 -3.353857E-09 Coma 5th ord X 5 4
-3.639932E-07 5 5 4.083817E-10 Pentafoil X
6 0 1.082787E-09 Hexafoil Y 6 1
2.653164E-09 6 2 -5.562098E-09 6 3
-5.657147E-08 Spherical 5th 3rd Focus 6
4 2.971023E-09 6 5 8.877737E-10 6 6
-4.649130E-06 Hexafoil X
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Surface figure cooldown of SW ZnSe S2
Surf fig rms 2.74nm
Zernike coeffs for surface S2 deformation (mm)
N M A(N,M) 0 0 2.525041E-10 Piston 1
0 2.993422E-10 X-tilt 1 1 7.632050E-10
Y-tilt 2 0 -5.971137E-09 Astigmatism -45
2 1 -3.263482E-06 Focus shift 2 2
5.627774E-09 Astigmatism 0 or 90 3 0
-4.283727E-10 Trefoil Y 3 1 1.133856E-07
Coma 3rd ord Y 3 2 5.183714E-08 Coma 3rd
ord X 3 3 -5.874208E-06 Trefoil X 4 0
8.810965E-10 Tetrafoil Y 4 1 1.763393E-09
4 2 8.018278E-07 Spherical 3rd Focus 4 3
-4.894394E-10 4 4 -9.632704E-10 Tetrafoil X
5 0 1.724538E-10 Pentafoil Y 5 1
-6.425059E-10 5 2 5.631900E-09 Coma 5th ord
Y 5 3 2.292512E-09 Coma 5th ord X 5 4
-2.042380E-07 5 5 8.014672E-11 Pentafoil X
6 0 -1.364540E-09 Hexafoil Y 6 1
3.202912E-09 6 2 -7.377090E-10 6 3
1.018624E-06 Spherical 5th 3rd Focus 6 4
3.032352E-09 6 5 -1.312308E-09 6 6
-2.458051E-06 Hexafoil X
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Differences in transmitted WFE in NIRCam SW Path
at 2.0mm for 5 field points from cool-down
mount-induced surface figure changes SW ZnSe
lens
rms 2.15nm
rms 2.08nm
rms 2.48nm
rms 2.09nm
rms 1.97nm
Prediction is 2.48 nm versus 8.02 budget
allocation
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Bonding Tests

• Sample lens substrates with metal pucks attached
  have successfully been cryo-cycled to 16K
• Characterization of epoxy samples for CTE and
  other properties is underway
• Margin of safety test has been designed with
  testing to occur in June

Test Article
Margin of Safety Tests
Epoxy samples for testing.
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ETU Build Flow
August ?
Delivery to GSFC in Oct.