aster/tir activities in the last years - grss | ieee · pdf fileigarss 2011, july 24‐29,...

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)


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%)


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


Degradation Since the Launch


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


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


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


Typical Experimental System for Land Sites

Single‐band radiometer

Multi‐band radiometer

Portable blackbody

Weather station

Other instruments: FTIR, thermal camera, etc.

radiosonde


Typical Experimental System for Water Sites

Single‐band radiometer

Multi‐band radiometer

Thermistor buoys

Other instruments: Weather station, Thermal Camera, etc.

radiosonde


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


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.


BT difference between VC and OBC as a function of time

IU: Ibaraki UniversityNIES: National Institute for Environmental StudiesJPL: Jet Propulsion Laboratory


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


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.




Straylight effectC

Below 270 K(Less accuracy)


Lake Kussharo (Japan)

• Coldest VC site (below 270K)

• ASTER’s designed accuracy is 2K for this temperature range




Straylight effectC

Below 270 K(Less accuracy)

CLarge spatial variation


Mauna Loa (HI)

• Pahoehoe lava flow

• Not good for VC due to large spatial variation


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


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


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)

aster/tir activities in the last years - grss | ieee · pdf fileigarss 2011, july 24‐29,...

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