Calibration & Validation Methodologyseminar.utmspace.edu.my/eoss2007/Material/Session4/... ·...

©2007, ATSB Proprietary

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RazakSATTM

Calibration & Validation

Methodology

21stNovember 2007

Presented by:

Astronautic Technology (M) Sdn Bhd


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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


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.



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




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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




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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



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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




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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

23

45

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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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12

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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 ––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 ––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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flight vicarious calibration ––Field work

Field work

Solar radiometer

Spectroradiometer

θs

θv

Φs

Target surface


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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

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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.


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Thank you

Thank you

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