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NIRCam: A 40 Megapixel
Camera for JWST
Marcia Rieke
NIRCam P.I.
A Competitor
39 million pixels
• The H2D-39 uses a 39
megapixel sensor that is
more than twice the
physical size of today’s
35mm sensor….
• You only need to spend
$33K to get nearly as
many pixels as NIRCam
So what do you get for your extra $100M for a NIRCam?
-- a camera that works from 0.6 to 5 microns, not just
from 0.36 microns to 0.8 microns and which can survive
the space environment
2
NIRCam Partners
• Science Team from Arizona, JPL, Rochester Institute
of Technology, Canada, Hawaii, Switzerland, Spitzer
Science Center, NASA Ames
• Lockheed-Martin in Palo Alto, CA, is responsible for
design and construction of the most of the
instrument
• Arizona is procuring detectors from Teledyne
Imaging Systems in Camarillo, CA, and will deliver
them to L-M after characterization and assembly into
mosaics
• Space Telescope Science Institute will operate
NIRCam after launch: Current NIRCam Team
includes Jay Anderson, Massimo Robberto, and
Kailash Sahu
3
Full Science Team
Science Theme Leads
Chas Beichman (Debris Disks &Planet.Systems)
JPL
Daniel Eisenstein (Extragalactic)
University of Arizona
Michael Meyer (Star Formation)
University of Arizona
Team Members
Stefi Baum Roch. Institue of Tech
Simon Lilly
ETH
Laura Ferrarese HIA/DAO
Peter Martin
University of Toronto
René Doyon Université de Montréal
Don McCarthy (EPO Lead) U of Arizona
Alan Dressler
Carnegie
George Rieke
University of Arizona
Tom Greene
NASA Ames
Tom Roellig
NASA Ames
Don Hall
University of Hawaii
John Stauffer
Spitzer Science Center
Klaus Hodapp University of Hawaii
John Trauger
JPL
Scott Horner Lockheed Martin ATCr
Erick Young
University of Arizona
Doug Johnstone HIA/DAO
Associated scientists: Doug Kelly, John Stansberry, Christopher Willmer, Karl Misselt,
Chad Engelbracht (Az), John Krist (JPL)
4
NIRCam Design Features
• NIRCam images the 0.6 to 5mm (1.7 - 5mm prime) range
– Dichroic used to split range into short (0.6-2.3mm) and long (2.4-5mm)
sections
– Nyquist sampling at 2 and 4mm
– 2.2 arc min x 4.4 arc min total field of view seen in two colors (40
MPixels)
– Coronagraphic capability for both short and long wavelengths
• NIRCam is the wavefront
sensor
– Must be fully
redundant
– Dual filter/pupil
wheels to
accommodate
WFS hardware
– Pupil imaging
lens to check
optical
alignment
5
Dichroic Provides Two Channels Per Module
Short wavelength channel
Long wavelength channel
•The majority of NIRCam
exposure time will be
used for deep survey
observations over the 7
wide band filters
•Survey efficiency is
increased by taking
observations of the same
fields in long wave and
short wave bands
simultaneously
Module B
SW:0.6mm - 2.3mm
LW: 2.4 mm to 5 mm
Module A
Each module has two
spectral wave bands
6
NIRCam’s Role in JWST’s Science Themes
NIRCam
NIRCAM_X000
Modern Universe
Clusters &
Morphology
Reionoization
First Galaxies
Recombination
Forming Atomic Nuclei
Inflation
Quark Soup
The First Light in the Universe:
Discovering the first galaxies, Reionization
NIRCam executes deep surveys to find and
categorize objects.
Period of Galaxy Assembly:
Establishing the Hubble sequence, Growth of
galaxy clusters
NIRCam provides details on shapes and colors
of galaxies, identifies young clusters
Stars and Stellar Systems: Physics of the IMF,
Structure of pre-stellar cores, Emerging from the
dust cocoon
NIRCam measures colors and numbers of stars
in clusters, measure extinction profiles in dense
clouds
young solar system
Kuiper Belt
Planets
Planetary Systems and the Conditions for
Life: Disks from birth to maturity, Survey of
KBOs, Planets around nearby stars
NIRCam and its coronagraph image and
characterize disks and planets, classifies
surface properties of KBOs
7
1000
NIRCam Science
Requirements
– Highest possible sensitivity – few nJy
sensitivity is required.
100
nJy
• Detection of first light objects,
studying the epoch of reionization
requires:
5-s 50,000 secs
10
1
0.1
0.5
1.5
– High spatial resolution for
distinguishing shapes of galaxies at
the sub-kpc scale (at the diffraction
limit of a 6.5m telescope at 2µm).
Space (HST or SPITZER)
JWST
z=5.0
z=10.1
Performance of adopted filter set
Number of
Filters
4
5
6
4
Number of
Filters
• Observing the period of galaxy
assembly requires in addition to
above:
4.5
Point source sensitivities for 50,000 sec
exposures and 5:1 signal-to-noise ratio. The z=10
galaxy has M=4x108M and the z=5 galaxy has
M=4x109M.
5
6
7
4
Number of
Filters
– A filter set capable of yielding ~4% rms
photometric redshifts for >98% of the
galaxies in a deep multi-color survey.
3.5
l(
mm)
Ground (Keck/VLT)
– Fields of view (~10 square arc minute)
adequate for detecting rare first light
sources in deep multi-color surveys.
2.5
5
6
7
8
0.00
1<Z<2
0.05
2<Z<5
0.10
|Zin-Zout|/(1+Zin)
8
5<Z<10
0.15
0.20
NIRCam Science Requirements cont’d
• Stars and Stellar Systems:
– High sensitivity especially at l>3mm
– Fields of view matched to sizes of star clusters
( > 2 arc minutes)
– High dynamic range to match range of
brightnesses in star clusters
– Intermediate and narrow band filters for
dereddening, disk diagnostics, and jet studies
– High spatial resolution for testing jet
morphologies
• Planetary systems and conditions for life
requires:
– Coronagraph coupled to both broad band and
intermediate band filters
– Broad band and intermediate band filters for
diagnosing disk compositions and planetary
surfaces
9
Derived Requirements
• nJy (10-35 W/m2/Hz) sensitivity
– Detectors with read noise < 9 e-, Idk<0.01 e/sec QE>80%
– Focal plane electronics with noise < 2.5e- so detector
performance is not degraded
– High throughput instrument: 70% for optics, 85% for
filters
• At least 7 broadband filters for redshift estimates
• Large Field of View
– Dichroics to double effective FOV
– Large format detector arrays
• Large well-depth on detectors
• High spatial resolution
– Nyquist sampling at 2mm and 4mm
10
Derived Requirements cont’d
• Selection of intermediate and narrowband filters
– 8 R~10 filters needed to classify ices, cool stars
– At least 4 R~100 filters for key jet emission lines (want
higher spatial resolution than Canadian tunable filters)
• Coronagraph required in all modules
– Coronagraph most important at long wavelengths
– Coronagraphic field must not reduce survey FOV
• Need fluxes calibrated to 2%
– Requires gain stability on week time scales
– Requires on-orbit calibration plan using on stars
11
Field of View Layout
12
NIRCam as Wavefront Sensor:
Initial Capture and Alignment
•Telescope focus sweep
•Segment ID and Search
•Global alignment
•Image stacking
•Coarse phasing
•Fine phasing
•Multi-field fine phasing.
First Light
After
segment
capture
Coarse
phasing
w/DHS
•
•
Spectra recorded
by NIRCam
DHS at pupil
Fine phasing
•
After coarse phasing
Fully aligned
NIRCam provides the imaging data needed for
wavefront sensing.
Two grisms have been added to the long
wavelength channel to extend the segment
capture range during coarse phasing and to
provide an alternative to the Dispersed
Hartmann Sensor (DHS)
Entire wavefront sensing and control process
demonstrated using prototypes on the Keck
telescope and on the Ball Testbed Telescope.
13
Coarse Phasing with the Dispersed
Hartmann Sensor
DHS is collection of grisms
and wedges that are placed
in the NIRCam pupil wheel.
Every segment pair is
covered by one grism so
coarse phasing consists of
measuring spectra to
determine the offset in the
focus direction between
segments.
Process is robust even if a
segment is missing.
Initial errors
Max piston error=19 mm
Rms=5 microns
After correction
Max piston error=0.66 mm
Rms=0.18 microns
A prototype DHS
was tested on
Keck.
14
NIRCam Optical Train Today
11
3
10
12
4
5
9
2
6
1
13
7
1
Pick-off Mirror assembly **
2
Coronagraph
3
First Fold Mirror
4
Collimator lens group
5
Dichroic Beamsplitter
6
Longwave Filter Wheel Assembly
7
Longwave Camera lens group
8
Longwave Focal Plane
9
Shortwave Filter Wheel Assembly
10
Shortwave Camera lens group
11
Shortwave Fold Mirror
12
Pupil Imaging Lens **
13
Shortwave Focal Plane
** These items + bench design
changed from original proposal
8
•
ETU will have
– Only one Module (B)
– No LW Channel
– No Coronagraphic
capability
15
Coronagraph Concept
Coronagraph
Image
Masks
JWST Telescope
NIRCam
Pickoff
Mirror
Collimator
Optics
Telescope
Focal
Surface
Camera
Optics
Pupil
Wheel
Filter
Wheel
Coronagraph
Wedge
Not to scale
Not to scale
Coronagraph
Image Masks
FPA
NIRCam
Optics
Field-of-View
Without Coronagraph Wedge
Calibration Source
FPA
Collimator
Optics
With Coronagraph Wedge
Wedge
16
Camera
Optics
Planet Observations
Simulation by John Krist
17
100 Myr-Old, 2 MJup Planet
18
Shortwave Optical Path
SW FPA Flat
SW Camera Triplet
SW FPA
SW Fold Flat
Dichroic
Beamsplitter
Filter(s)
6
17
:0
5
1:
MM
50
50
0.
e:
al
c
S
FFM
125.00
o OTE 03/02/04
POM
Scale:
0.20
Lenses fabricated from either
LiF, BaF2 or ZnSe.
MM
Collimator Triplet
10-Mar-05
m
Ca
IR
no
Mo
OT
E
03
/
02
04
/
19
.0
0
Longwave Optical Path
LW FPA Flat
LW FPA
LW Camera Triplet
09
1:
:0
17
Filter(s)
Dichroic
Beamsplitter
MM
.
50
50
0.
e:
al
Sc
FFM
Mono OTE 03/02/04
Collimator Triplet
4
POM
Scale:
m
0.21
Ca
NI
R
M
/0
02
/
03MM
119.05
E
OT
o
on
10-Mar-05
20
00
-M
10
WFE Performance
Predicted WFE through SW Filters
80
70
Requirement
(nm rms)
50
Prediction
(nm rms)
40
30
20
10
0
2
N
N
N
N
M
M
M
W
0W 90W
0W 50W 0W
08
64
87
12
62
82
10
7
1
00
1
1
1
2
1
1
2
5
0
0
1
1
2
F
F
F
F
F
F
F
F
F
F
F
F
F1
Predicted WFE through LW Filters
200
150
Requirement
(nm rms)
100
Prediction
(nm rms)
50
F4
70
N
F4
60
M
F4
44
W
F4
30
M
F4
05
N
F3
56
W
F3
35
M
F3
00
M
0
F2
70
W
WFE
WFE
60
21
Transmission
Transmission vs Wavelength
100%
90%
Requirement: >
66%
70% @ 1.1
microns
micron
80%
70%
T
60%
SW
LW
50%
40%
30%
20%
10%
0%
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Wavelength (microns)
22
5
Pathfinder - COL and SW Cam Singlets
ZnSe Singlet
Singlet with Vibe Fixture
LiF Singlet
23
Pathfinder DBS – Thermal Test to 105 K
White Chamber
Pathfinder
DBS
Thermal Strap
Interface Plate
Cold Table
24
SW Camera Assy – Thermal Vac Testing
White Chamber
Pathfinder DBS
SW Cam Assy
Thermal Straps
Interface Plate
Cold Table
25
Pupil Imaging Lens (“The PIL”)
A pupil imaging lens was added to NIRCam to assist with
aligning NIRCam to the telescope and to provide pupil data
to the wavefront sensing algorithm.
Qual unit pupil imaging lens
26
FAM Role in NIRCam
The NIRCam Focus and Alignment Mechanism (FAM)
contains the Pick-Off Mirror (POM), the first element in the
NIRCam optical train. It has the capability to position the
POM in 3 degrees of freedom; focus, tip, and tilt.
POM
Assembly
Sensor
&
Target
Assy
Linear
Actuators
27
NIRCam Filter Wheels
• Both the long and the short wave
channels have dual-filter wheel
assemblies
• The first wheel is located at the
NIRCam pupil and is referred to as the
pupil wheel
• The second wheel is referred to as the
filter wheel
Longwave FWA
Dichroic Beam Splitter
Shortwave FWA
Filter/pupil wheels
include extra cal
features.
Longwave Camera
Shortwave Camera
28
NIRCam Filters
4
F150W2
3.5
F322W2
3
F164N F187N F212N
2.5
F405N F418N F466N F470N
PP
P
P
2
PP
F225N
1.5
F140M
PF182MF210M
F162M
1
0.5
F323N
F150W
F115W
F090W
F070W
F250M F300M
F200W
F277W
F460M
F360M F410MF430M
F335M
F356W
F480M
F444W
0
0.5
1.5
2.5
3.5
4.5
5.5
l(mm)
29
Pupil Wheel
Calibration Source & Projectors
Pupil Alignment Pinhole
Projector
Flat Field Projector
Calibration Light Source
30
• Primary technique for JWST coarse segment phasing uses 2
Dispersed Hartmann Sensors (prism arrays); reduces phase offsets
from ~100 mm to < 1mm (PSF is sensitive to even larger errors)
– Each prism covers 2 segments; fringes produced when segment
offsets cause pos / neg interference as function of wavelength
– Has been successfully demonstrated on Keck
• 2 identical grisms (rotated 90 deg) are being added as a backup for
coarse phasing technique, but they will also enable science
– Dispersed Fringe Sensing: tilt of dispersed fringe yields segment
piston
– Also validated on Keck (90-142 nm RMS error)
– Each grism covers all segments
– Grisms in series with a LW filter
– High dispersion @ long wavelengths gives large
capture range
Grism 1: Horizontal
Dispersion
31
Grism 2: Vertical
Dispersion
Grism Motivation
Grism: Design
•
4950 nm
4700 nm
Y=0.000
•
65 gv/mm design meets WFS
requirements
Maximum piston listed is from the
red-spectral DFS algorithm with short
wavelength end starts from center of
spectral range
Minimum piston listed comes from
fringe tilt detected by using
differential centroid of the crosssection profile between long and
short wavelength ends
– Centroiding accuracy determines
the minimum piston detection.
(s = 1/20 pixel is used)
15:49:04
•
Spectra Positions on FPA of a Point
Source at the Center of the Field
3950 nm
3700 nm
3200 nm
2950 nm
36.7 mm
LW FPA size 36.7 X 36.7 mm
Center Field Dispersion by Grism
12.9
SURFACE 45
MM
09-Feb-07
NIRCam Mono OTE 03/02/04
Grism
Wavelength
Range
NIRCam Filters
Maximum
Piston
Minimum
Piston
Grism
Thickness
65.0 gv/mm
3.30 – 5.0 mm
F322W (partial), F356W, F444W
±291 mm
±0.12 mm
Min = 3.3 mm,
Max = 8.5 mm
75.0 gv/mm
3.30 – 5.0 mm
F322W (partial), F356W
(partial), F444W
±344 mm
±0.12 mm
Min = 3.5 mm,
Max = 9.8 mm
32
Near IR Detectors
• Three instruments (NIRCam, NIRSpec,
FGS/TFI) use the same detectors. NIRCam
uses two flavors of HgCdTe, 2.5mm and
5.2mm cut-off material.
• Basic format is 2040x2040 with 4 reference
pixels around the periphery
• Performance is great – dark current at 37K
is ~.005 e/sec, QE is > 80% over the full 0.6 5mm range
Three development detectors in test
dewar.
180000
3.5E+06
2.5E+06
2.0E+06
140000
120000
Electrons
3.0E+06
No. of pixels
160000
Read Noise: median
is 7.5 electrons in
1000 sec.
1.5E+06
100000
80000
60000
Well depth is nearly 2x
the required 60,000
electrons.
1.0E+06
40000
5.0E+05
20000
0
0.0E+00
0
5
10
15
20
Read noise in 1000 secs (electrons)
25
30
0
100
200
300
Time(secs)
33
400
500
Other Properties
Excellent, too!
14
12
.025% of full well
10
ADUs
8
Cumulative
6
4
2
0
Dark current floor
-2
0
20
40
60
Time (sec)
2mm flat
Differential
fields. Flats
show little
wavelength
dependence.
80
100
120
• HgCdTe material is now
produced by molecular beam
epitaxy rather than liquid
phase epitaxy which
produces much more
uniform and high quality
material.
0.5
1.0
34
16300
Detector
Result: Using
Reference
Pixels
16250
16200
ADU_
16150
16100
16050
16000
15950
15900
0
500
1000
1500
2000
2500
Sample No. (~10.6sec/sample)
C034 Cooling
Ref pixels
Detector pixel
25000
1) Correct for drifts in
the readout
electronics (upper
panel)
_
DC Level in ADU _
Reference pixels act
like detector pixels
electrically. They
can be used to
24000
23000
22000
21000
20000
30
40
50
60
70
80
T(K)
Ref pixel
Detector pixel
Fit
90
2) Correct for drifts due
to temperature
changes (lower
panel)
35
“Popcorn” Noise
Not Quite Perfect!
Time 
Interpixel Capacitative
Coupling
Reset Anomaly
19500
19000
ADU
_
18500
18000
17500
17000
16500
0
200
400
600
800
1000
Time (secs)
998 1163
1008 1783
36
Producing Mosaics
Four arrays () are
mounted to create a
4Kx4K mosaic ().
• After SCAs (sensor chip assemblies) are
produced at Teledyne, they will be mounted
with minimal gaps to produce a 4Kx4K
mosaic for NIRCam’s short wavelength arm.
• Location of SCAs within the mosaic will be
verified by using a precise measuring
microscope which can measure the location
of a surface to better than 10 microns in all
three coordinates.
• Mosaicing done at
Steward.
37
FPA Mock-up
Assembled FPA less
SCAs and the mask. All
parts can be machined
in Tucson, most on
campus.
Mask to cover gaps and
bond wires.
Ti
flexure.
38
FPA Assembly Verification
Insert Plates
Black Epoxy Visible
Through Plastic
FPA Baseplate
39
FPA Heater Assembly Verification
Mosaic Baseplate
Temperature
Sensors
Titanium Struts
Heater
40
ETU Bench is
finished!
41
Why Being PI Isn’t Fun!
42
NIRCam is on its way!
• Much of the NIRCam Engineering Test Unit
hardware has been delivered to Palo Alto with
the ETU to be delivered to Goddard early
next year.
• Collection of detector calibration data in
progress.
• Some flight hardware is also already in hand.
The flight unit is to be delivered in the spring
of 2010.
43