Post on 03-Jul-2020
©2007, ATSB Proprietary
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RazakSATTM
Calibration & Validation
Methodology
21stNovember 2007
Presented by:
Astronautic Technology (M) Sdn Bhd
©2007, ATSB Proprietary
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RazakSAT
RazakSAT™™
Cal/Val Objective
Cal/Val Objective
�Calibration:To correct the possible bias
caused by degrading sensor perform
ance.
�Validation:To ensure the calibration
activities has corrected the bias induced.
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Elements of sensor calibration
Elements of sensor calibration
Main elements comprises:
�Spectral calibration
�Radiometric calibration
�Geometric calibration
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Spectral calibration
To determ
ine sensor’s response at different wavelengths,
where the response as a function of wavelength
measured and characterised for each spectral band.
Elements of sensor calibration
Elements of sensor calibration
760-890nm
Band 4 (NIR)
630-690nm
Band 3 (red)
520-600nm
Band 2 (green)
450-520nm
Band 1 (blue)
RazakSAT
RazakSAT™™(MAC
(MAC))
Parameters
Parameters
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Radiometric calibration
Quantitatively defining the system response to a known
reference signal input.
These includes:
�Detector response linearity
�Detector pixel offset and response variation
�Absolute radiometric calibration
Elements of sensor calibration
Elements of sensor calibration
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Geometric calibration
To characterise geometric anomalies that due to optical
aberrations or misalignment of discrete m
ultiple detectors
These includes:
�Line of sight
�Effective focal length
�Field of view
Elements of sensor calibration
Elements of sensor calibration
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Pre-flight calibration
To characterise system perform
ance based on designed
requirements.
�Perform
ed in laboratory under
controlled environment.
�Spectral, radiometric and geometric
included.
Calibration approaches
Calibration approaches
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In-flight calibration
To characterise system perform
ance in orbit during
satellite’s lifespan.
�Launch and Early Orbit Operations (LEOPS)
�Includes spectral, radiometric and geometric
�Vicarious method
Calibration approaches
Calibration approaches
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Validation on data products in 3 steps:
1.Acquisition of image data and derivation of inform
ation
2.Independent ground m
easurements at invariant
condition
3.Comparison of system inform
ation and independent
ground m
easurements
Validation
Validation
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1.Pre-flight sensor calibration & response function
correction
2.In-flight atmospheric correction
3.In-flight sensor calibration
4. In-flight sensor perform
ance evaluation & validation
RazakSAT
RazakSAT™™
Calibration Overview
Calibration Overview
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RazakSAT
RazakSAT™™
Cal / Val processing flow
Cal / Val processing flow
Pre-flight calibration
Satellite launched
In-flight calibration
Ground measurement
Result Validation
Calibration Coefficients
Timely update
Applied to RazakSATTMimage
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RazakSAT
RazakSAT™™
Pre
Pre-- Flight Calibration
Flight Calibration
Overview
Overview
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Measurement Case
Measurement Case
Definition
Measurement cases are made to simulate different illumination level that would be
received by M
AC during imaging in-orbit. Each measurement case defines different
sets of illumination level generated through different combinations of lamps from
Integrating Sphere..
1 2 3 4 5 6 7 8 9 10
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12
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Measurement Cases
Integrating Sphere
Tungsten
Halogen
Xenon
MAC FPA
Expected
Output
(Albedo
unit)
PAN : 0.3
Blue : 0.12
Green : 0.24
Red : 0.35
NIR : 0.63
DN Number
Linearity Response
SNR
Saturation Level
Dark Response
Actual
Measurement
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CSTM
CSTM-- XTH4000
XTH4000-- V Lamps Characteristic
V Lamps Characteristic
Tungsten
Halogen
Xenon
Tungsten Halogen+ Xenon
Xenon & Tungsten Halogen Characteristic
All Lamps On (Xenon + Tungsten Halogen)
Combination of Xenon lamps and Tungsten Halogen
lamps necessary to achieve specified spectrum,
peak radiance, luminance range and variability
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Albedo Estimation For Measurement Case
Albedo Estimation For Measurement Case
NIR
Red
Green
Blue
PAN
CASES
1.63
1.49
1.34
1.00
1.38
CASE13
0.82
0.85
0.80
0.62
0.80
CASE12
0.04
0.41
0.50
0.48
0.43
CASE11
0.06
0.62
0.75
0.72
0.64
CASE10
0.84
1.06
1.04
0.86
1.01
CASE9
0.44
0.83
0.89
0.78
0.82
CASE8
0.22
0.13
0.09
0.04
0.11
CASE7
0.63
0.35
0.24
0.12
0.30
CASE6
1.87
1.04
0.70
0.33
0.88
CASE5
1.47
0.82
0.55
0.26
0.69
CASE4
0.94
0.52
0.35
0.17
0.44
CASE3
0.68
0.38
0.26
0.12
0.32
CASE2
0.30
0.17
0.12
0.06
0.14
CASE1
Radiance
in Albedo
Unit
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
01
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PAN
B G R IR
Expected Albedo from Measurement Cases
Note:
Note:
Estimation of Albedo for each m
easurement case was m
ade by itera
Estimation of Albedo for each m
easurement case was m
ade by iteration process
tion process
to ensure that all ranges of albedo (0.01 ~ 1.1) will be tested
to ensure that all ranges of albedo (0.01 ~ 1.1) will be tested for each band of
for each band of
interest (M
AC Band)
interest (M
AC Band)
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Pre
Pre-- Flight Calibration Scenario
Flight Calibration Scenario
Focal
Plane
Assembly
LOW
MEDIUM LOW
MEDIUM
MEDIUM HIGH
HIGH
1 2 3 4 5 6 7 8 9 10
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Measurement Cases
Integrating Sphere
RazakSAT™
MAC
Gain Setting
Data Analysis
Downlink
Processing
IRPS
Linearity Response
Non-Uniform
ity
Dark Response
Saturation Level
SNR
Offset Level
Non-Uniform
ity
Dynamic Range
Output
Radiometric
Signal
Processing
Unit 1
Signal
Processing
Unit 2
Focal
Plane
Assembly
LOW
MEDIUM LOW
MEDIUM
MEDIUM HIGH
HIGH
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Output Summary
Output Summary
Saturation Level
SNR
Offset Level
Non-Uniform
ity
Dynamic Range
To define the baseline that needs to be subtracted from signal
obtained during illumination so that the user-interest signal can
be obtained
Digital Number of MAC output has reach its maximum
To define the dynamic range of reliability between lower end of
dark response and upper end towards saturation
Linearity
Response
Gain Variations
To define the ratio of pure signal received over noise generated
in the system
Dark Response
MAC
Mathematical
Modeling
(Radiometric)
Radiometric
Calibration
Coefficient
Announcement
of Opportunity
To define
RazakSAT™
Applications
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RazakSAT
RazakSAT™™
InIn-- Flight Calibration
Flight Calibration
Plans & Overview
Plans & Overview
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Atmospheric Correction
Atmospheric Correction--Concept
Concept
�Typical atmospheric
effect on radiance
reflected to optical
sensor.
�For instance, Water
leaving radiance
contains 10% of ocean
signal and 90%.
atmosphere signal.
�The atmospheric and
ocean effects must be
removed.
Extraterrestrial
solar radiance
Zenith
Diffuse
Ocean Water
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Atmospheric Correction
Atmospheric Correction ––Solar radiometry
Solar radiometry
�Solar radiometry is a common approach to
obtain a wide range of atmospheric parameters
�View the sun directly
�Knowing the sensor calibration allows us to
compute spectral transmittance
�Spectral transmittance can be used to determ
ine
aerosol, ozone, and water vapor amounts as well
as aerosol type
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Atmospheric Correction
Atmospheric Correction ––Solar radiometry
Solar radiometry
�For instance, sky radiance and irradiance data can
be used to provide more inform
ation regarding
aerosols
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InIn-- flight vicarious calibration
flight vicarious calibration --Objective
Objective
�It is observed that some visible channel of imagers
degrade in orbit.
�In-Flight vicarious calibration was perform
ed because
RazakSAT™
has no onboard calibration device.
�It is necessary to develop In-flight calibration coefficients
(or slopes) which take into account the in-orbit
degradation of the sensor so that the derived products
are rendered accurate.
�Vicarious technique is widely being used
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InIn-- flight vicarious calibration
flight vicarious calibration ––Field work
Field work
Solar radiometer
Spectroradiometer
θs
θv
Φs
Target surface
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InIn-- flight vicarious calibration
flight vicarious calibration ––Overall method
Overall method
Wavelength (nm)
Reflectance
500
1000
1500
2000
2500
0.00.10.20.30.40.5
Average Surface Reflectance Spectrum of Grass Target
Recorded between 11:49 and 12:10, June 30, 2000
Average of 108 Spectra
1 Std. Dev. Limits of Reflectance Variability
Air m
ass
ln Irradiance (Detector DN)
12
34
10.010.210.410.6
June 30, 2000 Evening Langley Plot at 521 nm
Linear Fit is Between 2 and 4 Air Mass
Extinction Equation
ln I = 10.8376 - 0.2115(Air m
ass)
Field target
measurement
Solar measurement
Radiative transfer Function
Calibration Product:
Sensor’s calibration Gain
Satellite signal
Analysis
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InIn-- flight Optical perform
ance evaluation
flight Optical perform
ance evaluation --MTF
MTF
�To evaluate on orbit electro-optical perform
ance.
�Bridge and its Line Spread Function,
Modulation Transfer Function
LSF
MTF
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InIn-- flight Optical perform
ance evaluation
flight Optical perform
ance evaluation --MTF
MTF
•Convex mirrors and its Point
Spread function, Modulation
Transfer Function
PSF
MTF
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Conclusion
Conclusion
RazakSAT™
Cal/Val is a practical approach that
satisfies our purposes of perform
ing calibration
and validation.
©2007, ATSB Proprietary
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Thank you
Thank you