MODIS Thermal Band Radiance Cal/Val
Chris Moeller
Cooperative Institute for Meteorological Satellite Studies,
University of Wisconsin
with contributions from
Jack Xiong, MODIS Characterization Support Team (MCST), GSFC
Dave Tobin, Cooperative Institute for Meteorological Satellite Studies
Simon Hook, Jet Propulsion Laboratory (JPL, NASA)
CoRP Cal/Val Symposium
July 13, 2005
Outline
•
•
•
•
•
Brief MODIS background
Cal/Val procedure
MODIS L1B validation findings
Contributions to Uncertainty
Summary
Instrument Background
•
2-sided Paddle Wheel Scan Mirror
–
–
•
3 Nadir Spatial Resolutions
–
PFM
FM1
•
–
Aqua (EOS-PM):
Launched on 05/04/02
First light 06/24/02
•
Reflective solar bands (1-19, and 26),
thermal emissive bands (20-25, 27-36)
On-Board Calibrators (OBCs):
–
–
–
–
Terra (EOS-AM):
Launched on 12/18/99
First light on 02/24/00
VIS, NIR, SMIR, and LWIR
36 Spectral Bands (490 detectors)
–
•
250m (1-2), 500m (3-7), and 1km (8-36)
4 Focal Plane Assemblies (FPAs)
–
•
(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)
Solar diffuser (SD)
SD stability monitor (SDSM)
Blackbody (BB)
Spectro-radiometric calibration assembly
(SRCA)
Space view (SV)
Science Applications
–
–
Land, oceans, and atmosphere
Nearly 40 science products generated and
distributed
Page 3
MODIS TEB Calibration Using
Blackbody
RVS: Response Versus Scan-angle
: Emissivity
Radiance (TOA), LEV
LEV
1
2

a0  b1  dnEV  a2  dnEV
  RVS SV  RVS EV   LSM 

RVS EV
Calibration coefficient, b1, from BB
b   RVS    L   RVS  RVS   L  RVS   1     
1
BB
BB
BB
SV
BB
SM
BB
BB
L: Spectral band averaged radiance
dn: Digital count with background
corrected
cav
2
 Lcav  a0  a2  dnBB
 / dnBB
Page 4
Table 1. MODIS spectral and radiometric characteristics.
MODIS
Thermal IR
Band No.
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
CWL
(Bandwidth)
(m)
3.788 (3.70-3.88)
3.992 (3.96-4.04)
3.971 (3.93-4.02)
4.057 (4.01-4.10)
4.473(4.43-4.52)
4.545 (4.50-4.59)
1.382 (1.36-1.40)
6.765 (6.64-6.89)
7.337 (7.17-7.50)
8.524 (8.34-8.71)
9.730 (9.58-9.88)
11.014 (10.76-11.27)
12.018 (11.78-12.27)
13.361 (13.21-13.51)
13.679 (13.52-13.84)
13.911 (13.74-14.08)
14.194 (14.06-14.33)
Radiometric
Accuracy
Specification*
0.75% (0.18 K)
10.0% (3.0 K)
1.0% (0.25 K)
1.0% (0.25 K)
1.0% (0.19 K)
1.0% (0.24 K)
Reflectance Band
1.0% (0.27 K)
1.0% (0.32 K)
1.0% (0.53 K)
1.0% (0.42 K)
0.5% (0.34 K)
0.5% (0.37 K)
1.0% (0.61 K)
1.0% (0.58 K)
1.0% (0.55 K)
1.0% (0.47 K)
* for typical earth scene radiance of that band
MAS
Equivalent
Band No.
30
31
31
32
NONE
35
NONE
NONE
NONE
42
43
45
46
48
49
49
50
CWL
(Bandwidth)
(m)
3.725 (3.66-3.81)
3.900 (3.83-3.98)
3.900 (3.83 3.98)
4.050 (3.98-4.13)
4.503 (4.44-4.58)
8.563 (8.34-8.74)
9.642 (9.45-9.88)
11.002 (10.79-11.24)
12.032 (11.80-12.25)
13.186(13.02-13.38)
13.952(13.63-14.15)
13.952 (13.63-14.15)
14.302 (14.16-14.52)
Primary
Use
Surface/Cloud Temp.
Fire detection.
Surface/Cloud Temp.
Surface/Cloud Temp.
Atmospheric Temp.
Atmospheric Temp.
Cirrus Detection
Water Vapor
Water Vapor
Water Vapor, Cloud
Ozone
Surface/Cloud Temp.
Surface/Cloud Temp.
Cloud Top Properties
Cloud Top Properties
Cloud Top Properties
Cloud Top Properties
MODIS IR Spectral Bands, MAS FWHM
MODIS Spectral Response Functions and FASCOD3P Brightness Temperature
Spectrum at HIS Resolution (U.S. Standard Atmosphere; 0-30km)
Relative Response
0.5
280
0.4
260
0.3
34
0.2
35
240
36
0.1
32
31
30
33
220
Brightness Temperature (K)
300
0.0
650
700
750
800
850
900
950
1000
1050
1100
-1
Wavenumber (cm )
300
0.3
300
Relative Response
24
0.4
280
28
280
0.2
0.3
27
260
260
25
0.2
240
0.1
0.1
240
23
29
22
20
220
0.0
1100
220
0.0
1200
1300
1400
1500
Wavenumber (cm-1)
1600
2200
2400
2600
Wavenumber (cm-1)
2800
Brightness Temperature (K)
0.5
Why are high altitude aircraft
useful for Cal/Val work?
• Direct observation of integrated upwelling
radiance, closely simulating on-orbit sensors.
• Uncertainty dominated by airborne instruments
• Mobile laboratory. Aircraft meets the satellite
at a chosen time/place.
• Covers several thousand km2 in 10 minutes
(lots of samples).
TX-2002 ER-2 Payload
NPOESS Atmospheric
Sounder Testbed
(NAST-I)
Video Imaging
System (VIS)
Dual RC-10 Camera
Scanning High Resolution
Interferometer Sounder
(SHIS)
MODIS Airborne
Simulator (MAS)
Cloud Physics Lidar
(CPL)
• MAS - 50 channel VIS/IR spectrometer, 50 m res., 36 km swath
• SHIS - Scanning M/LWIR 0.5 cm-1 interferometer, 2 km res, 32 km swath
• CPL – micropulse dual polarization lidar, 15 m res, nadir only
• NAST-I – Scanning MWIR/LWIR interferometer, 2km res, 40 km swath
• RC-10 - b/w and false color IR photo, 1-5 m res., 15 x 15 km coverage
• VIS video imaging system - color video CCD camera; continuous
MODIS Emissive Band
Cal/Val from the
ER-2 Platform
2. Transfer SHIS calibration to MAS
1. Collect MODIS and ER-2 co-incident data
MODIS on
Terra
MAS, SHIS
on ER-2
q
705 km
20 km
MODIS
Footprint
36 km
3. Co-locate MODIS FOV on MAS
2000
2001
Terra
MODIS
2002
Aqua MODIS
SAFARI-2000
WISC-T2000
2003
THORpex-2003
TX-2001
CLAMS
2004
2005
Tahoe-2004
TX-2002
MAS and SHIS data sets collected on the NASA ER-2 aircraft have been key for directly
assessing Terra and Aqua MODIS L1B accuracy.
Terra
MODIS
4
CO2
wv
11 12
CO2
MODIS spec. given by box
Detector averaged
Terra
MODIS
11 um
04/01/01
Along Track Profile
The Lake Tahoe 2004 field activity evaluated Terra MODIS radiometric performance.
Buoy Sites
12um
4
CO2
wv
SHIS April 9, 2004 - Night Run 09
5
11 12
CO2
Detector averaged
tr1
tr2
tr3
tr4
average
4
3
1
0
-1
-2
-3
-4
-5
8
MAS_SHIS Simulated MODIS BT (K)
Vertical bars represent radiometric accuracy spec.
MODIS Band Number
SHIS
SHIS
2
Predicted - Measured BT (K)
11um
3.9um
Terra
MODIS
Predicted – Measured
Brightness Temperature (K)
3.7um
MAS_SHIS - MODIS (K)
MODIS Observed BT (K)
April 9, 2004
0544 UTC
9
10
11
12
Wavelength (um)
Wavelength (um)
13
MODIS Residual (K)
Aqua
MODIS
4
CO2
wv
CO2
TX-2002 Experiment
Assess Aqua MODIS
Cal/Val
Detector dependent
(atmospheric bands)
11 12
Detector averaged
MODIS Band Number
Aqua
Nov. 21, 2002
1941 UTC
Detector dependent
(window bands)
Nov 21, 2002
MAS
B45 (11 um)
Uncertainties
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•
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SHIS calibration uncertainty
Altitude correction
Geolocation error (spatial mismatch)
Temporal mismatch
Sunglint influence
SHIS Accuracy
Blackbody Geometry
AERI, NAST, S-HIS, GIFTS
2.70 IN.
APERTURE
BLACKBODY
CAVITY
HEATER
CASE
THERMISTORS
(2 SENSE, 1 CONTROL)
THERMAL
INSULATION
THERMISTOR
(APEX)
CAVITY SUPPORT
(THERMAL ISOLATOR)
ELECTRICAL
CONNECTOR
HANDLE
Aperture Diameters
AERI: 2.7”
S-HIS: 1.6”
NAST: 1.0”
SHIS Expected Performance
TABB = 227K, THBB = 310K
SW
MW
LW
Atmospheric Pressure (mb)
ER-2
Level
MODIS B30, 9.6um (Ozone)
MODIS B33, 13.3um (CO2)
MODIS B35, 13.9um (CO2)
MODIS B36, 14.2um (CO2)
MAS B43, 9.6um (Ozone)
MAS B48, 13.2um (CO2)
MAS B49, 13.8um (CO2)
MAS B50, 14.3um (CO2)
Normalized Weighting Function
Influence of Altitude Difference between MODIS and MAS
Atmospheric absorption above
the ER-2 altitude (20 km) is
important for O3 and CO2
sensitive bands.
O3
CO2
Spatial Uncertainty
Temporal Uncertainty
Sun Glint:
magnifies spatial and
temporal uncertainty
in 4um region
What Are We Learning?
• Cal/Val of MODIS L1B is viable, even
necessary, from high altitude aircraft.
• MODIS meets spec in almost all bands.
• Detector striping is corroborated by Cal/Val.
• MODIS radiometric biases can be cautiously
applied to L2 products, e.g. CO2 cloud heights.
Back-up Slides
SCAN
TRACK
The MODIS spatial weighting function was measured in the scan and
track directions during prelaunch testing using a 0.1 x 10 FOV slit
stepped across the MODIS focal planes. Idealized smearing was
added to the scan direction measurements to simulate the effect of the
scan mirror motion.
APRIL 01, 2001
November 21, 2002
April 9, 2004