MODIS On-orbit Calibration Methodologies › workshops › ivos05 › pres › 03_xiong.pdf · MODIS On-orbit Calibration Methodologies Jack Xiong and Bill Barnes NASA/GSFC, Greenbelt,

MODIS On-orbit Calibration Methodologies

Jack Xiong and Bill BarnesNASA/GSFC, Greenbelt, MD 20771, USA

University of Maryland, Baltimore County, Baltimore MD, 21250, USA(Support provided by entire MCST Analysts Team)

CEOS-IVOS at ESA / ESTEC, Noordwijk, Netherlands (12-14 October, 2004)

Outline

• Introduction• Instrument background• MODIS On-orbit Calibration Methodologies

(performance examples included)– Overview of MODIS on-orbit calibration and

characterization– Radiometric calibration of reflective solar bands (RSB)– Radiometric calibration of thermal emissive bands (TEB)– Spectral characterization (RSB only)– Spatial characterization (RSB and TEB)

• Challenging Issues• Summary

Page 2

• The MODerate Resolution Imaging Spectroradiometer (MODIS)is the keystone instrument for the NASA’s Earth ObservingSystem (EOS)

• MODIS is on both Terra and Aqua spacecraft. Terra (EOS-AM)launched on 12/18/99; Aqua (EOS-PM) launched on 05/04/02– http://terra.nasa.gov/– http://eos-pm.gsfc.nasa.gov/

• Broad range of applications– Land, oceans, atmosphere– Close to daily global coverage– Morning & afternoon observations

Page 3

Introduction

MODIS Characterization Support Team

Page 4

• MODIS Science Team Leader: Vince Salomonson– Land, Ocean, and Atmospheric Groups– MODIS Support Teams

• MODIS Characterization Support Team (MCST)• Science Data Support Team (SDST)• MODIS Administration Support Team (MAST)

• MCST Responsibilities– Support MODIS instrument operations– Maintain and update L1B code and LUTs– Design and improve algorithms; perform instrument calibration and data

analysis; provide science support on instrument issues

– MCST Calibration Workshops (starting from pre-launch)– MsWG (MODIS Sensor Working Group)

• Science Group Representatives and Instrument Vendor

Instrument Background

Page 5

VelocityVector

• 36 spectral bands– Reflective solar bands (1-19,

and 26)– Thermal emissive bands (20-

25, 27-36)• 3 nadir spatial resolutions

– 250m (1-2), 500m (3-7), and1km (8-36)

• On-Board Calibrators:– Solar diffuser (SD)– SD stability monitor (SDSM)– Blackbody (BB)– Spectroradiometric

calibration assembly (SRCA)– Space View (SV)

• 2-sided Paddle Wheel Scan Mirror– (10km by 2330 km swath per 1.478 sec)– Day data rate = 10.6 Mbps, night data

rate = 3.3 Mbps (100% duty cycle, 50%day and 50% night)

OPTICAL SYSTEM

VIS

SC

AN

TRACK

BA

ND

12

11

93

47

15

VIS FOCAL PLANE

SC

AN

TRACK

BA

ND

19

14

12

21

14

15

16

17

SC

AN

TRACK

BA

ND

12

11

93

47

15

15

15

15

SWIR/MWIR

FOCAL PLANE

NIR FOCAL PLANE

W

N

E

S

TRACK

SCAN

5.5°

19.371

14°

14°

SC

AN

TRACK

BA

ND

12

11

93

47

15

15

15

15

LWIR

FOCAL PLANE

19.371

MODIS Optics System

Page 6

Page 7

MODIS Key Specifications

Primary Use Band Bandwidth 1 Spectral

Radiance 2

Required

SNR 3

Primary Use Band Bandwidth 1 Spectral

Radiance 2

Required

NE!T(K)4

1 620 - 670 21.8 128 20 3.660 - 3.840 0.45 (300K) 0.05

2 841 - 876 24.7 201 21 3.929 - 3.989 2.38 (335K) 0.2

3 459 - 479 35.3 243 22 3.929 - 3.989 0.67 (300K) 0.07

4 545 - 565 29 228 23 4.020 - 4.080 0.79 (300K) 0.07

5 1230 - 1250 5.4 74 24 4.433 - 4.498 0.17 (250K) 0.25

6 1628 - 1652 7.3 275 25 4.482 - 4.549 0.59 (275K) 0.25

7 2105 - 2155 1 110 26 1.360 - 1.390 6 150 3

8 405 - 420 44.9 880 27 6.535 - 6.895 1.16 (240K) 0.25

9 438 - 448 41.9 838 28 7.175 - 7.475 2.18 (250K) 0.25

10 483 - 493 32.1 802 Cloud Properties 29 8.400 - 8.700 9.58 (300K) 0.05

11 526 - 536 27.9 754 Ozone 30 9.580 - 9.880 3.69 (250K) 0.25

12 546 - 556 21 750 31 10.780 - 11.280 9.55 (300K) 0.05

13 662 - 672 9.5 910 32 11.770 - 12.270 8.94 (300K) 0.05

14 673 - 683 8.7 1087 33 13.185 - 13.485 4.52 (260K) 0.25

15 743 - 753 10.2 586 34 13.485 - 13.785 3.76 (250K) 0.25

16 862 - 877 6.2 516 35 13.785 - 14.085 3.11 (240K) 0.25

17 890 - 920 10 167 36 14.085 - 14.385 2.08 (220K) 0.35

18 931 - 941 3.6 57

19 915 - 965 15 250

4 NE!T = Noise-equivalent temperature difference

3 SNR = Signal-to-noise ratio

1 Bands 1 to 19 are in nm; Bands 20 to 36 are in µm

Land/Cloud/Aerosols

Properties

Ocean Color/

Phytoplankton/

Biogeochemistry

Atmospheric Water

Vapor

2 Spectral Radiance values are (W/m

2-µm-sr)

Surface/Cloud

Temperature

Atmospheric

Temperature

Cirrus Clouds Water

Vapor

Surface/Cloud

Temperature

Land/Cloud/Aerosols

Boundaries

Cloud Top Altitude

Page 8

MODIS On-orbit CalibrationMethodologies and Performance

• Overview of MODIS on-orbit calibration andcharacterization– On-orbit calibration schematic

Page 9

Moon

SDSM

ScanMirror

SolarDiffuser

SRCA

Blackbody

SpaceView

On-orbit Calibration Schematic

SDSM

BB warm-up/cool-down, quarterlySD/SDSM, weekly (bi-weekly)SRCA radiometric, monthlyLunar calibration, monthly (S/C roll maneuvers)

Page 10

• Overview of MODIS on-orbit calibration and characterization– On-orbit calibration schematic

• Radiometric calibration of reflective solar bands (RSB)– On-board solar diffuser (SD) and solar diffuser stability monitor

(SDSM)– Lunar observations


Page 11

RSB Calibration Using SD/SDSM

SD

SD

Sun

dc

dc! =

Scan Mirror

Sun

1.44% Screen

SDSM

SD

Optional 7.8% Screen

m1=

BRFSD!cos "

SD( )< dn

SD

*> !d

Earth# Sun

2! $

SD! %

SD

Reflectance factor !EV " cos #EV( ) = m1 " dnEV*

"dEarth$Sun2

ΔSD: SD degradation factor;ΓSD: SD screen vignetting functiond: Earth-Sun distancedn*: Corrected digital numberdc: Digital count of SDSM

Page 12

MODIS RSB Calibration Using the Moon

SD Calibration

m1=

BRFSD!cos "

SD( )< dn

SD

*> !d

Earth# Sun

2! $

SD! %

SD

m1 =f (view _ geometry)

< dnMoon*

>

Moon Calibration

f =fphase!angle

" flibration

" fover! sampling

dSun!Moon2

" dModis!Moon2

Why and How?

Page 13

9 %

12 %

MS1

MS2

Terra RSB (B9 and B17) Response Trending

Band (wavelength), Detector, and Mirror Side Dependent Calibration

Terra and Aqua RSB Response Trending

Aqua MODIS: less degradation

AOI dependent

11.2°

38°

50.2°

Wavelength dependentB8 at 412nm, B17 at 905nm

Page 14

Noticeable mirror sidedifference (Terra)

Little mirror sidedifference (Terra)

Page 15

Terra and Aqua SD degradation Trending

m1=

BRFSD!cos "

SD( )< dn

SD

*> !d

Earth# Sun

2! $

SD! %

SD

SD

SD

Sun

dc

dc! =

Similar SD Degradation for BothTerra and Aqua MODIS

SD door fixed at open with SD screen in place

Page 16




• Radiometric calibration of thermal emissive bands (TEB)– On-board Blackbody (BB)


Page 17

MODIS TEB Calibration Using Blackbody

RVSEV!L

EV+ RVS

SV" RVS

EV( ) ! LSM

= a0+ b

1! dn

EV+ a

2! dn

EV

2

RVSBB!"

BB! L

BB+ RVS

SV# RVS

BB( ) !LSM + RVSBB! 1 # "

BB( ) !"cav ! Lcav

= a0+ b

1! dn

BB+ a

2! dn

BB

2

Radiance (TOA), LEV

Calibration coefficient, b1, from BB

RVS: Response Versus Scan-angleε: EmissivityL: Spectral band averaged radiancedn: Digital count with background corrected

b1

Page 18

MODIS TEB Calibration Using Blackbody

BB from 270-315Kprovides a0 and a2

BB at T_BB provides b1on a scan-by-scan basis

Page 19

Terra MODIS TEB Response Trending

Page 20

Aqua MODIS TEB Response Trending

Page 21





• Spectral characterization (RSB only)– On-board Spectro-radiometric calibration assembly (SRCA)


Page 22

To MODIS scan mirror

SRCA COLLIMATOR

Integration sphere

Filter wheel

Focusing mirror

Collimating mirror

MONOCHROMATOR

LIGHT SOURCE

Grating

Entrance slit

Didymium filter

Calibration SiPD

Exit slit

Reference SiPD

Motor

To MODIS scan mirror

SRCA COLLIMATOR

Integration sphere

Filter wheel

Focusing mirror

Collimating mirror

MONOCHROMATOR

LIGHT SOURCE

Grating

Entrance slit

Didymium filter

Calibration SiPD

Exit slit

Reference SiPD

Motor

MODIS Spectral Calibration Using SRCA

_

2sin( ) cosoffsetgrati half ang gln e

A

m! " " #= $ + $Grating Equation

Self-calibration using didymium filter peaks

Page 23

On-orbit Terra MODIS (B3, B4, B8, and B9)Relative Spectral Response (RSR)

Terra MODIS, Band 3

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.450 0.455 0.460 0.465 0.470 0.475 0.480 0.485

Wavelength (µm)

RS

R

Prelaunch

2000061

2001099

2002109

2003125

2004028

Terra MODIS, Band 4

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.535 0.540 0.545 0.550 0.555 0.560 0.565 0.570

Wavelength (µm)

RS

R

Prelaunch

2000061

2001099

2002109

2003125

2004028

Terra MODIS, Band 8

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.398 0.402 0.406 0.410 0.414 0.418 0.422 0.426

Wavelength (µm)

RS

R

Prelaunch

2000061

2001099

2002109

2003125

2004028

Terra MODIS, Band 9

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.432 0.436 0.440 0.444 0.448 0.452

Wavelength (µm)

RS

R

Prelaunch

2000061

2001099

2002109

2003125

2004028

Page 24

Terra and Aqua MODIS RSB (λ<1µm) On-orbit Band Center Wavelength Shift

Terra Aqua

Band Cneter wavelength ( µm) 2000061 2001099 2002109 2003125 2004112 2002171 2003118 2004118

1 0.6463 0.4 0.2 0.2 0.2 0.2 0.2 0.5 0.4

2 0.8564 0.5 0.0 0.2 0.0 -0.1 0.8 1.2 1.2

3 0.4657 0.2 0.0 0.0 -0.1 -0.1 0.1 0.0 0.0

4 0.5537 0.2 -0.1 0.0 -0.1 -0.1 0.0 0.1 0.1

8 0.4119 -0.5 -0.7 -0.6 -0.5 -0.5 0.1 0.3 0.3

9 0.4422 -0.2 -0.4 -0.5 -0.5 -0.5 0.1 0.1 0.2

10 0.487 -0.2 -0.3 -0.4 -0.5 -0.4 0.1 0.1 0.1

11 0.5298 0.0 -0.2 -0.3 -0.3 -0.3 0.0 0.1 0.0

12 0.5469 0.2 -0.1 -0.1 -0.2 -0.2 0.1 0.2 0.1

13 0.6657 0.1 -0.1 -0.3 -0.3 -0.2 0.1 0.1 0.2

14 0.6769 0.3 0.0 -0.1 -0.1 -0.1 0.2 0.2 0.2

15 0.7465 0.0 -0.2 -0.3 -0.3 -0.2 0.1 0.2 0.1

16 0.8664 -0.1 -0.4 -0.5 -0.4 -0.4 0.1 0.1 0.1

17 0.9042 0.1 -0.1 -0.1 -0.1 0.0 0.2 0.2 0.1

18 0.9357 -0.1 -0.4 -0.6 -0.6 -0.4 0.1 0.0 0.1

19 0.9363 0.1 0.0 -0.2 -0.4 -0.1 0.2 0.5 0.4

yyyyddd

Page 25





• Spectral characterization (RSB only)– On-board Spectro-radiometric calibration assembly (SRCA)

• Spatial characterization (RSB and TEB)– On-board Spectro-radiometric calibration assembly (SRCA)


Page 26

MODIS Spatial Calibration Using SRCA

Reticles

To MODIS

Integration sphereBeam -splitter in filter wheel

IR sourceEntrance opening

To MODIS

Integration sphereBeam -splitter in filter wheel

IR sourceEntrance opening

Along-scanAlong-track

Mirror

0

0

( , , )

( , )

( , , )

x

x

N

x

N

x

dn b ch x x

x b ch

dn b ch x

=

=

!

="

"

Page 27

MODIS Spatial Calibration Using SRCA

0

0

( , , )

( , )

( , , )

x

x

N

x

N

x

dn b ch x x

x b ch

dn b ch x

=

=

!

="

"

Terra SRCA signal for each individual phase-delayBand 8 channel 5

0

50

100

150

200

250

300

350

400

1 2 3 4 5 6 7 8 9 10 1 1 1 1 1 1 1 1 1 20 2 2 2 2 2 2 2 2 2 30 3 3 3 3 3 3 3 3 3 40 4 4 4 4 4 4 4 4 4 50 5 5 5 5 5 5 5 5 5 60

dn

PD_0 PD_4PD_3PD_2PD_1 PD_5

Not in use

Terra SRCA signal combined from all phase-delays Band 8 channel 5

0

50

100

150

200

250

300

350

400

0 1 2 3 4 5 6 7 8 9 10 11

X

dn

Phase-delay introduced

Along-Scan Examples

Challenging Issues

Page 28

• No valid pre-launch measurements for Terra MODIS TEB RVS• At-launch RVS derived from witness sample reflectance and parameters

from Aqua MODIS RVS measurements• C-NAD relative RVS to improve imagery• DSM RVS to improve radiometry

• SDSM sun view signal ripples caused by a design error• Modeling and simulation• Alternative approach

• Terra MODIS PC optical leak• Lunar observation

• SWIR crosstalk (thermal leak and electronic crosstalk)• Improvement with a linear correction algorithm• Additional calibration error and striping

Challenging Issues

Page 29

• Tracking RSB response change• Mirror side, wavelength, AOI dependent (on-orbit RVS)

• SD calibration uncertainty (impact on ocean)• RSB BRF pre-launch characterization uncertainty (spatial non-uniformity

can cause annual oscillation in response trending)• No SD vignetting function characterized pre-launch (Yaw maneuvers)• Noisy detectors (additional error and striping)• Earthshine impact (0.2%)

• MWIR crosstalk (electronic crosstalk)• B21 calibration• Polarization sensitivity change (ocean color)

Page 30

• Instruments performed better than overall design specifications– Terra (+4.5 years) and Aqua (+2.0 years)– Constant calibration and characterization efforts

• Thermal Emissive Bands (16 bands and 160 detectors)– Terra MODIS

• Stable short-term and long-term response trending (excluding sensorconfiguration change and instrument reset events)

• 20 (10 from pre-launch, B36) noise detectors and 0 inoperable detectors

– Aqua MODIS (similar and better)• Better response trending than Terra MODIS• 1 (1 from pre-launch) noise detectors and 0 inoperable detectors

Summary

Page 31

• Reflective Solar Bands (20 bands and 330 detectors)– Terra MODIS

• Noticeable optics degradation (wavelength dependent, mirror side, andAOI dependent)

• 21 (20 from pre-launch, band 7) noise detectors and 0 inoperable detectors– Aqua MODIS (more stable)

• Noticeable optics degradation (wavelength dependent)• 3 noise detectors and 15 (13 from pre-launch, band 6) inoperable detectors

• Stable Spectral and Spatial Performance for Both Terra and Aqua

• Useful Experience and Lessons Learned– Terra MODIS => Aqua MODIS– MODIS => NPOESS and NPP VIIRS

Summary

Documents

MODIS On-orbit Calibration Methodologies › workshops › ivos05 › pres › 03_xiong.pdf · MODIS On-orbit Calibration Methodologies Jack Xiong and Bill Barnes NASA/GSFC, Greenbelt,