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TRANSCRIPT
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
MODIS On-orbit CalibrationMethodologies and Performance
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
• 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
• Radiometric calibration of thermal emissive bands (TEB)– On-board Blackbody (BB)
MODIS On-orbit CalibrationMethodologies and Performance
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
• 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
• Radiometric calibration of thermal emissive bands (TEB)– On-board Blackbody (BB)
• Spectral characterization (RSB only)– On-board Spectro-radiometric calibration assembly (SRCA)
MODIS On-orbit CalibrationMethodologies and Performance
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
• 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
• Radiometric calibration of thermal emissive bands (TEB)– On-board Blackbody (BB)
• Spectral characterization (RSB only)– On-board Spectro-radiometric calibration assembly (SRCA)
• Spatial characterization (RSB and TEB)– On-board Spectro-radiometric calibration assembly (SRCA)
MODIS On-orbit CalibrationMethodologies and Performance
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