Focal Plane Array Testing
and Applications for
Astronomy
Donald Figer
Space Telescope Science Institute
Outline

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The role of detectors in discovery.
The state of the art in detectors.
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Keck/LGS/AO
HST
SOFIA
Detectors and future Astronomy projects.
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LSST
SNAP
JWST
The Role of Detectors
Detector Functions

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Photometry
Astrometry
Spectoscopy
Morphology
Time Variability
Detector Types

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Eye
Film
Photomultiplier tube
CCD
Photodiode array
Radio Antennae
Detector Wavelength Sensitivity
X-ray
Visible
0.1 0.3
Silicon
NIR
0.9 1.1 2.5
MIR
5
HgCdTe
InSb
InGaAs
l [mm]
20
CCD Architecture
Hybrid Architecture
Hybrid Architecture
In
bump
light-sensitive layer
substrate
AR coating
Keck
Keck
Keck
Keck/AO/LGS
HST: Hubble Space Telescope

General-purpose orbiting astronomical
telescope
HST
HST
HST
HST
HST
SOFIA: Stratospheric Observatory for
Infrared Astronomy
LSST: Large Synoptic Survey
Telescope

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What is the distribution of dark matter in
the Universe?
What is dark matter?
LSST
SNAP: Supernova Acceleration
Probe

What is dark energy?
SNAP Optical Configuration
Telescope is a three-mirror anastigmat
2.0 meter aperture
1.37 square degree field
Lightweight primary mirror
Low-expansion materials
Optics kept near 290K
Transverse rear axis
Side Gigacam location
passive detector cooling
combines Si & HgCdTe detectors
Spectrometers share Gigacam focal
plane
Few moving parts in payload
two-blade shutter for Gigacam
focussers/adjusters at secondary & tertiary
SNAP Focal Plane Concept


Coalesce all sensors at one focal
plane.
 Imager sensors on the front.
 36 HgCdTe 2kx2k 18 mm
 36 CCD 3.5kx3.5k 10.5 mm
 Filters
 1 of 3 per HgCdTe
 4 of 6 per CCD
 Spectrograph on the back with
access ports through the focal
plane.
Exposure times of 300 s with
four/eight exposures in
CCDs/HgCdTe.
JWST: James Webb Space
Telescope
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What is the shape of the Universe?
How do galaxies evolve?
How do stars and planetary systems form
and interact?
How did the Universe build up it present
elemental/chemical composition?
What is dark matter?
JWST
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6.5m diameter primary mirror
launch in 2013
orbit at L2
four scientific instruments
JWST deployment movie
IDTL: Independent Detector
Testing Laboratory

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Located at Space Telescope Science
Institute and Johns Hopkins University
Founded 1999
Mission: Serve the astronomical
community by developing and testing
detectors for space and ground based
astronomy programs
Past and Present Personnel
Eddie Bergeron
Data Analyst
Tom Reeves
Lab Technician
Robert Barkhouser
Optical Engineer
Mike Telewicz
Intern
Bernie Rauscher
Project Scientist
Utkarsh Sharma
Graduate Student
Gretchen Greene
Mechanical Engineer
Steve McCandliss
JHU Lead
Ernie Morse
Data Analyst
Monica Rivera
Intern
Scott Fels
Intern
Don Figer
Director
Russ Pelton
Technician
Sito Balleza
Systems Engineer
Mike Regan
System Scientist
IDTL Test System
He Lines
IDTL Test System
Figure 3.3. Mechanical drawing of cross section of IDTL dewar assembly. The
optics with ray trace are also shown.
Figer et al. 2002, SPIE, 4850, 981
IDTL Sample Results:
Persistence (1200 seconds)
IDTL Sample Results: Read
Noise
IDTL Sample Results: Dark
Current
IDTL Sample Results
Dark Current
Dark Current
Read Noise
Short-wave Cutoff
Persistence
RQE vs. T
Gain
Long-wave Cutoff
IDTL Comparartive Detector
Characterization
Properties of Silicon: QE
Properties of Silicon: Long Wave
QE
Silicon 1 mm QE vs. Thickness &
Temperature
Properties
of
HgCdTe
• Nearly “ideal” characteristics.
• Many vendors.
Properties of InGaAs: QE
State
of
the
Art:
Thin
CCD
• Nearly “ideal” characteristics.
• Many (~4) vendors.
State of the Art: LBNL Thick CCD
QE
State
of
the
Art:
Si
PIN
• Emerging technology.
• Chief Vendors - Raytheon Vision Systems (RVS) and Rockwell
Scientifics Corp. (RSC).
Comments / Notes
Parameter
Read Noise
< 10e- with multiple reads
2
Dark Current ~ 1fA/cm , @-100C
Radiation
Tolerance
Robust
On Chip
logic
Yes (on stacked ROIC)
Readout
Method
many choices, ripple, snap shot, subframe imaging, pseudo random
Support
Generally requires multiple biases but
State of the Art: Si PIN RQE (100
mm thick)
1
1
140 K
0.9
140 K
0.9
160 K
160 K
180 K
180 K
200 K
0.8
0.7
0.7
0.6
0.6
0.5
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0
400
500
600
700
800
Wavelength (nm)
900
1000
200 K
0.8
1100
0
800
850
900
950
Wavelength (nm)
1000
1050
1100
State of the Art: Si PIN Hybrid
Arrays
 Si PIN Hybrid QE Measures Data (from B.
Pain, et. al.)
State of the Art: Si PIN Dark
Current
Si PIN Dark Current versus Temperature
Dark Current (e-/s/pixel)
1.E-10
Dark Current (A/cm^2)
1.E-11
1.E-12
Temperature (K)
100
dark current 0.0001
120
140
160
180
200
220
0.0001 0.0004
0
0.4
14
300
1.E-13
0.001 in
e-/s/pixel
for 10(18
mm pixel
noise
H2RG-003
• QE@ 1mm
1.E-15
mm pixels)
• 24%@140K
• 28%@160K
1.E-16
• 1e- on reference pixels,
• 33%@180K
1.E-17 Fowler-32, 100 kHz
• 38%@200K
1.E-18
• 9e- on science pixels,
• Crosstalk, 2-3%
90 100 110 100
120 kHz
130 140 150 160 170 180 190 200 210 220
Fowler-32,
• Persistence, <0.3%
Temperature (K)
well depth, 120,000 e-
 1.E-14
read

230
State of the Art: Si PIN Read
Noise
10 e-
State of the Art: HgCdTe
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Mature technology, although short-wave QE is
recent development.
Several vendors.
Flight heritage
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NICMOS, 256x256, 2.5um cutoff.
Hubble Wide Field Camera 3, H1RG, 2.3um cutoff.
(Launch?)
Deep Impact MRI spectrometer, H1RG, 5um cutoff.
JWST NIRCam, NIRSpec, FGS, 2.5um and 5.0um
cutoff. (Launch?)
State of the Art: HgCdTe Dark
Current
State of the Art: HgCdTe Read
Noise
State
of
the
Art:
InGaAs
• Emerging technology.
• Sensors Unlimited
State
ofcontract
the Art:
SUI InGaAs
 DARPA
to develop
1280 x 1024QE
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InGaAs Array.
Dark current goal of 2nA/cm2.
Read noise ~ 10e- at video rates.
Worth watching.
State of the Art: Photon Counting
CCD
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Emerging technology.
Two (more?) vendors.
Low Light Level CCDs (L3CCDs), a.k.a.
EMCCDs.
Realized noise is 1.4 times value for non-photon
counting mode.
High read rate required in photon counting mode
implies high power ~10 W per CCD for clocks
and outputs.