View
19
Download
0
Category
Tags:
Preview:
DESCRIPTION
- PowerPoint PPT Presentation
Citation preview
MODIS Thermal Band Radiance Cal/Val
Chris MoellerCooperative 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 SymposiumJuly 13, 2005
Outline
• Brief MODIS background
• Cal/Val procedure
• MODIS L1B validation findings
• Contributions to Uncertainty
• Summary
Instrument Background
Page 3
• 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)
• 3 Nadir Spatial Resolutions– 250m (1-2), 500m (3-7), and 1km (8-36)
• 4 Focal Plane Assemblies (FPAs)– VIS, NIR, SMIR, and LWIR
• 36 Spectral Bands (490 detectors)– Reflective solar bands (1-19, and 26),
thermal emissive bands (20-25, 27-36)• On-Board Calibrators (OBCs):
– 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
Terra (EOS-AM):Launched on 12/18/99First light on 02/24/00
PFM
Aqua (EOS-PM):Launched on 05/04/02 First light 06/24/02
FM1
Page 4
MODIS TEB Calibration Using Blackbody
2EV 0 1 EV 2 EV SV EV SM
EV
1L a b dn a dn RVS RVS L
RVS
/21 BB BB BB SV BB SM BB BB cav cav 0 2 BB BBb RVS L RVS RVS L RVS 1 L a a dn dn
Radiance (TOA), LEV
Calibration coefficient, b1, from BB
RVS: Response Versus Scan-angle
: EmissivityL: Spectral band averaged radiancedn: Digital count with background corrected
MODIS IR Spectral Bands, MAS FWHM
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).
Cloud Physics Lidar (CPL)
Scanning High ResolutionInterferometer Sounder (SHIS)
Dual RC-10 Camera
Video Imaging System (VIS)
MODIS Airborne Simulator (MAS)
NPOESS Atmospheric Sounder Testbed (NAST-I)
• 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
TX-2002 ER-2 Payload
MODIS Emissive Band Cal/Val from theER-2 Platform
MODIS Footprint
36 km
MAS, SHISon ER-2
20 km
705 km
MODIS on Terra
1. Collect MODIS and ER-2 co-incident data
2. Transfer SHIS calibration to MAS
3. Co-locate MODIS FOV on MAS
Terra MODIS
2000
WISC-T2000SAFARI-2000
2001
TX-2001 CLAMS
2002Aqua MODIS
TX-2002
2003 2004 2005
THORpex-2003 Tahoe-2004
MAS and SHIS data sets collected on the NASA ER-2 aircraft have been key for directly assessing Terra and Aqua MODIS L1B accuracy.
MODIS spec. given by box
Along Track Profile
TerraMODIS11 um
04/01/01
Terra MODIS
Detector averaged
11 124 wvCO2
CO2
The Lake Tahoe 2004 field activity evaluated Terra MODIS radiometric performance.
April 9, 20040544 UTC
Buoy Sites
MAS_SHIS Simulated MODIS BT (K)
MO
DIS
Obs
erve
d B
T (
K)
MODIS Band Number
MA
S_SH
IS -
MO
DIS
(K
)
Terra MODIS
Vertical bars represent radiometric accuracy spec.Wavelength (um)
Pred
icte
d –
Mea
sure
d B
righ
tnes
s T
empe
ratu
re (
K)
SHIS
SHIS April 9, 2004 - Night Run 09
-5
-4
-3
-2
-1
0
1
2
3
4
5
8 9 10 11 12 13
Pred
icte
d - M
easu
red
BT (K
)
tr1
tr2
tr3
tr4
average SHIS
Detector averaged
11 124 wvCO2
CO23.7um 3.9um
11um 12um
MODIS Band Number
MO
DIS
Res
idua
l (K
) Aqua MODIS
Nov. 21, 20021941 UTC
Aqua
Nov 21, 2002MAS
B45 (11 um)
Detector averaged
Detector dependent(window bands)
TX-2002 Experiment Assess Aqua MODIS
Cal/Val Detector dependent(atmospheric bands)
11 124 wv
CO2
CO2
Uncertainties
• SHIS calibration uncertainty
• Altitude correction
• Geolocation error (spatial mismatch)
• Temporal mismatch
• Sunglint influence
Blackbody Geometry AERI, NAST, S-HIS, GIFTS
BLACKBODYCAVITY
HEATER
CAVITY SUPPORT(THERMAL ISOLATOR)
HANDLE
ELECTRICALCONNECTOR
CASE
THERMALINSULATION
THERMISTORS(2 SENSE, 1 CONTROL)
2.70 IN.APERTURE
Figure n-n. AERI BLACKBODY
THERMISTOR(APEX)
Aperture DiametersAERI: 2.7”S-HIS: 1.6”NAST: 1.0”
SHIS Accuracy
SHIS Expected PerformanceTABB = 227K, THBB = 310K
SW
MW
LW
ER-2Level 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
Atm
osph
eric
Pre
ssur
e (m
b)
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
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.
TRACKSCAN
APRIL 01, 2001
November 21, 2002
April 9, 2004
Recommended