Transcript ESDC 2013 CMOS -

Improved Space Object Observation
Techniques using CMOS Detectors
T. Schildknecht, A. Hinze, J. Silha
Astronomical Institute, University of Bern, Switzerland
J. Peltonen, T. Säntti
Aboa Space Research Oy (ASRO), Turku, Finland
T. Flohrer
Space Debris Office, ESA/ESOC, Germany
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Outline
1. Optical Space Object Observation Strategies
 requirement for new detector
2. CMOS Imaging Sensors
 potential benefits
3. Characterization of sCMOS Camera
4. Conclusion
Slide 2
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Ground-Based Surveys
Angular velocity
FoV dwell time
(3° FoV)
Epoch accuracy
(0.5")
Exposure time
Detector readout
Ground-based
GEO
Ground-based
MEO/HEO
Ground-based
LEO
< 20"/s
<100"/s
200"/s –
1800"/s
540s @20"/s
108s @100"/s
~ 6s @1800"/s
25ms
5 ms
0.28ms
10 s ≥ 1s
10 s ≥ 1s
1s
few sec
few sec
1s
non-destructive
Processing
Electronic
shutter
streak det.
desired
Slide 3
desired
required
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Space-Based Surveys
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LEO sensor observing GEO/MEO/HEO
 similar to ground-based GEO/MEO/HEO
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Short-range observations
(small-size debris surveys)
 LEO to LEO, GEO to GEO, etc
 similar to ground-based LEO

Specific requirements
 mechanical shutters not advisable
 space-proof detector (cosmic ray background!)
 on-board processing desirable
Slide 4
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Generic Detector Requirements
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Detection, astrometry, photometry
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high quantum efficiency
Low read-out noise
low dark current
stable flat field (i.e. stable gain for each pixel)
stable bias or on-chip bias reduction
limited number of dark/hot pixels (“cosmetics”)
no charge leakage from pixel to pixel
limited enlargement of PSF in detector
high full-well capacity
Slide 5
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Requirements for New Detector
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Electronic shutter
 required for space-based sensor
 required for precise epoch registration (surveys LEO)
 increased reliability for ground-based sensors
Faster read-out (large sensors!)
 improved duty cycle
  larger survey area are per time
 more observations per tracklet (FoV crossing)
•  improved orbit accuracy
•  improved tracklet correlation
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Extremely short exposures 1s
 required for ground-based LEO, space-based short range
 non-destructive readout to “subdivide” streaks
On-chip processing
 spatial filtering
 image segmentation
Slide 6
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Silicon Detector Technologies
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Charge Coupled Devices (CCDs)
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CMOS sensors or Active Pixel sensors
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Hybrid Visible Sensors combining silicon photodiode
detection with separate CMOS electronics
Slide 7
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
CCD Detectors
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Basic structure/operation
principle
 array of photodiodes
 sequential readout (charge
transfer)
 one (or few) readout node(s)
 no electronic shutter
Alternative architectures
 “electronic shutter”
function
frame transfer
Slide 8
interline transfer
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
CMOS or Active Pixel Sensor
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Basic structure
/operation principle
 array of photodiodes
 each pixel has own
amplifier (and storage
area)
 multiplexed readout
Slide 9
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Hybrid Visible CMOS Imagers
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Combination of matrix of photodiodes with matrix
of CMOS multiplexers/amplifiers
Slide 10
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
On-chip processing in CMOS
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In CMOS processing in a pixelparallel fashion is possible
Back-illuminated circuits are
needed in astronomy. More
complex structures can be
integrated on the front surface
without too much reduction in
the photoactive area
ROI (region of interest) detection: Background subtraction,
filtering and simple (e.g. 1-bit) segmentation may be possible if
a local pixel storage for reference values can be established.
Paralleled, application specific image pipelines can be integrated
on the same chip outside the active area
Slide 11
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Main Advantages/Disadvantages
CCD
sCMOS
Hybrid CMOS
>90% (thinned)
60% with
microlenses
>90%
<2e- @560MHz
7-10e- @1MHz
~1:10-20 000
1:16 000
~1: 5 000
Uniformity
good
fair
fair
p2p Cross-talk
some
some?
some extra
Fast readout
<1fps
30-60 fps
30-60 fps
(yes)
rolling/global
rolling
fair/good
?
good
Quantum Eff.
(@500nm)
Read noise
Dynamic range
Electronic
shutter
Radiation tol.
6-10e- 1MHz
Complex
readout
no
random access; random access;
non.-destructive non.-destructive
Processing
no
limited on-chip
Slide 12
side-car
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Microlenses: Cross-Talk
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Problem if
numerical aperture of optical system <
numerical aperture of microlenses
Slide 13
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
sCMOS Camera Tests
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Andor NEO sCMOS (CIS2051, former Fairchild Imaging)
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11 bit intrinsic
16 "dual-gain"
front-side
QEmax 59 %
microlenses
Slide 14
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
sCMOS: Readout Noise
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2 single pixels (average of 1000 bias frames)
Slide 15
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
sCMOS: Readout Noise
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Noise distribution of (512x512 pixels, best case)
manufacturer spec.
CCD noise distribution
10x10 pixel area
Slide 16
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Non-Linearity
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High gain
 < 4%
(spec. <1%)
10 bit
11 bit
Slide 17
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Non-Linearity
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Low gain
 < 8%
(spec. <1%)
11 bit
11 bit
Slide 18
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Dual Gain
Slide 19
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Non-Linearity
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Dual gain
error in gate array?
14 bit
16 bit
Slide 20
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Flat Field Pixel Variance
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1000 flat fields, distrib. of single pixel variances
(512x512 pixel area)
1/8 * 3.5!

Slide 21
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Flat Field Pixel Variance
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1000 flat fields, single pixel variances
 ~9% interpolated pixels (average of 9 pixels)!
Slide 22
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Cross-Talk / MTF

2-d autocorrelation of difference of 2 flat fields
no explanation!.
Slide 23
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Conclusions
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Major challenges and design drivers for ground-based and
space-based optical observation strategies are
 detection of faintest objects
 precise epoch registration  electronic shutter
 short exposures 1s (LEO, space-based)
 high readout rate 1s for full frame (LEO, space-based)
 on-chip processing (space based)
CMOS Active Pixel Sensors
 offer most of the required capabilities
 but have still disadvantages wrt. CCDs
•
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low quantum efficiency (no backside illuminated devices)
noise characteristics
high Pixel Response Non-Uniformity (PRNU)
low dynamic range
high percentage of dark/hot pixles
Slide 24
Astronomical Institute University of Bern
T. Schildknecht: Improved Space Object Observation Techniques using CMOS Detectors
31th IADC Meeting, April 17 - 19, 2013, ESOC, Darmstadt, Germany
Conclusions
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Andor NEO sCMOS (CIS2051) camera has been
characterized by means of laboratory tests
 noise characteristics
 linearity, dynamic range
 cross-Talk / MTF
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Scientific CMOS devices are rapidly evolving and
some disadvantages may be overcome in near future
Slide 25
Astronomical Institute University of Bern