aster/tir activities in the last years - grss | ieee · pdf fileigarss 2011, july 24‐29,...
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IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
ASTER/TIR Vicarious Calibration Activities in the Last 11 Years
Hideyuki Tonooka (Ibaraki Univ.)Simon Hook (Jet Propulsion Laboratory)
Tsuneo Matsunaga, Soushi Kato (National Institute for Environmental Studies)
Elsa Abbott, Howard Tan (Jet Propulsion Laboratory)
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
ASTERAdvanced Spaceborne Thermal Emission and Reflection Radiometer
SubsystemBandNo.
Spectral Range (μm)
Spatial Resolution
VNIR
123N3B
0.52 ‐ 0.600.63 ‐ 0.690.78 ‐ 0.860.78 ‐ 0.86
15m
SWIR
456789
1.600 ‐ 1.7002.145 ‐ 2.1852.185 ‐ 2.2252.235 ‐ 2.2852.295 ‐ 2.3652.360 ‐ 2.430
30m
TIR
1011121314
8.125 ‐ 8.4758.475 ‐ 8.8258.925 ‐ 9.27510.25 ‐ 10.9510.95 ‐ 11.65
90m
Swath width = 60km
Developer: Ministry of Economy, Trade & Industry(METI)
Platform: NASA’s Terra (Launched in Dec. 1999)
Total scenes: Over 2 million scenes as of Jul. 2011(day: 85%, night: 15%)
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
ASTER/TIR Hardware and Calibration
• Mechanical scanning of 10 MCT detectors aligned along a track for each of 5 spectral bands
• Full‐aperture honeycombed blackbody which can change a temperature from 270 to 340 K
• No space viewing• Quadratic radiometric calibration equation
– Two‐temperature basis– Offset is determined for each Earth observation– Gain is given on a daily basis by prediction curves determined
from periodical calibration data – Non‐linearity is based on ground testing
• Designed accuracy of 1 K for a temperature range of 270 to 340 K
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
Vicarious Calibration for ASTER/TIR
At-sensor radiance
Pressure, Air temp., Humidity
Surface radiant temp. Surface temp.
Radiosonde, orNumerical forecast modelTOMS
Ozone
Surface emissivity
Radiative transfer
MODTRAN
OBC
Response functions
Elevation
Angle
Radiance-based Temperature-based
Its purpose is to validate at‐sensor radiances by ground experiments without onboard calibrator data
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
ASTER/TIR Vicarious Calibration Sites
• USA– Lake Tahoe (CA/NV)
– Salton Sea (CA)
– Cold Springs Reservoir (NV)
– Alkali Lake (NV)
– Railroad Valley (NV)
– Lunar Lake (NV)
– Coyote Lake (CA)
– Mauna Loa (HI)
• Japan– Lake Kasumigaura
– Lake Kussharo
(Blue) Water Sites (Red) Land Sites
Automated
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
JPL’s Semi‐Automated Validation System
• Lake Tahoe (1999–), and Salton Sea (2008–)• Skin and bulk water temperatures, and ground meteorological data
are logged and transferred to laboratory• Atmospheric profiles (water vapor, air temp. etc.) are obtained from
NCEP’s Global Data Assimilation System (GDAS) products
Skin temperature
Air temperature & Rel. Humidity
Wind Speed & Direction
LoggingSystem
BatteriesBulk WaterTemperature
3mASTL1A 1005201850471005230324
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
Typical Experimental System for Land Sites
Single‐band radiometer
Multi‐band radiometer
Portable blackbody
Weather station
Other instruments: FTIR, thermal camera, etc.
radiosonde
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
Typical Experimental System for Water Sites
Single‐band radiometer
Multi‐band radiometer
Thermistor buoys
Other instruments: Weather station, Thermal Camera, etc.
radiosonde
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
Browse Images for VC Sites
Lake Tahoe Salton Sea Railroad Valley& Cold Springs Res.
Lake Kasumigaura Lake Kussharo
Alkali Lake Lunar Lake& Railroad Valley
Coyote Lake Mauna Loa
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
Comparisons of brightness temperature (BT) between OBC and VC using 287 matchup data
Typically, OBC and VC agree within ±1 K for the water sites and within ±1.5 K for the dry lake sites.ASTER/TIR onboard calibrator has kept the expected accuracy in the wide temperature range (−10 to 45 C) since the launch.
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
BT difference between VC and OBC as a function of time
IU: Ibaraki UniversityNIES: National Institute for Environmental StudiesJPL: Jet Propulsion Laboratory
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
BT difference between VC and OBC for each experimental site
LT: Lake Tahoe, SS: Salton Sea, CS: Cold Springs Reservoir, LK: Lake Kasumigaura, KS: Lake Kussharo, AL: Alkali Lake, RV: Railroad Valley Playa, LL: Lunar Lake, CL: Coyote Lake, ML: Mauna Loa
Straylight effect
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
Cold Springs Reservoir (NV)
• Smallest VC site (1.6 km by 800 m)• Not good site for vicarious calibration due to straylighteffect [1][1] H. Tonooka, Inflight straylight analysis for ASTER thermal infrared bands,
IEEE TGARS, Vol. 43, pp. 2752‐2762, 2005.
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
BT difference between VC and OBC for each experimental site
LT: Lake Tahoe, SS: Salton Sea, CS: Cold Springs Reservoir, LK: Lake Kasumigaura, KS: Lake Kussharo, AL: Alkali Lake, RV: Railroad Valley Playa, LL: Lunar Lake, CL: Coyote Lake, ML: Mauna Loa
Straylight effectC
Below 270 K(Less accuracy)
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
Lake Kussharo (Japan)
• Coldest VC site (below 270K)
• ASTER’s designed accuracy is 2K for this temperature range
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
BT difference between VC and OBC for each experimental site
LT: Lake Tahoe, SS: Salton Sea, CS: Cold Springs Reservoir, LK: Lake Kasumigaura, KS: Lake Kussharo, AL: Alkali Lake, RV: Railroad Valley Playa, LL: Lunar Lake, CL: Coyote Lake, ML: Mauna Loa
Straylight effectC
Below 270 K(Less accuracy)
CLarge spatial variation
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
Mauna Loa (HI)
• Pahoehoe lava flow
• Not good for VC due to large spatial variation
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
BT difference between VC and OBC as a function of the precipitable water vapor
BT difference seems to be almost independent of PWV, indicating that the radiative transfer calculations were successfully made using accurate profiles
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
BT difference between VC and OBC as a function of the OBC BT
The difference seems to be positive in the lower temperature range, and be negative in the higher temperature range
IGARSS 2011, July 24‐29, 2011, Vancouver, Canada
Conclusions
• VC activities for ASTER/TIR have been continued by the ASTER science team since March 2000.
• 287 matchup data obtained by three organizations were analyzed– Some results indicate large BT differences due to straylight, low temperature, and large spatial variation effects
– No correlation between BT difference and PWV indicates that atmospheric profiles were successfully characterized even under humid conditions
– BT difference (VC–OBC) shows somewhat positive for low temperatures and negative for high temperatures
– Overall, OBC has been keeping the designed accuracy (1 K for the temperature range of 270 to 340 K)