HR: 1340h
AN: H13C-0444 [Abstracts]
TI: Identification and Characterization of Potential Ground Targets for Satellite Microwave Sensor
Calibration Monitoring
AU: * Savoie, M H
EM: savoie@nsidc.org
AF: Cooperative Institute for Research in Environmental Sciences (CIRES) National Snow and Ice Data Center
(NSIDC), UCB 449
University of Colorado, Boulder, CO 80309
United States
AU: Njoku, E
EM: eni.g.njoku@jpl.nasa.gov
AF: Jet Propulsion Laboratory (JLP), 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AU: Brodzik, M J
EM: brodzik@nsidc.org
AF: Cooperative Institute for Research in Environmental Sciences (CIRES) National Snow and Ice Data Center
(NSIDC), UCB 449
University of Colorado, Boulder, CO 80309
United States
AU: Knowles, K
EM: knowlesk@nsidc.org
AF: Cooperative Institute for Research in Environmental Sciences (CIRES) National Snow and Ice Data Center
(NSIDC), UCB 449
University of Colorado, Boulder, CO 80309
United States
AU: Armstrong, R L
EM: rlax@nsidc.org
AF: Cooperative Institute for Research in Environmental Sciences (CIRES) National Snow and Ice Data Center
(NSIDC), UCB 449
University of Colorado, Boulder, CO 80309
United States
AB:
AMSR-E (on Aqua) was launched in May 2002, one of a series of microwave radiometers on Earth-orbiting satellites that also
includes SMMR, SSM/I, TMI and AMSR (on ADEOS-II)and Windsat. These instruments all have onboard calibration systems designed
to enable calibrated brightness temperatures to be derived in the ground processing. However, all satellite radiometer data
require fine-tuning in the post-launch overall system calibration to remove residual radiometer and antenna system
calibration artifacts. These can arise from a variety of causes such as uncorrected attitude errors, instrument misalignment
or pointing errors, instrument thermal gradients, reflector emissivity errors, calibration coefficient errors, component
degradation, etc. Post-launch calibration fine-tuning usually involves finding suitable external targets, i.e., homogeneous
Earth surface areas of large spatial extent, such as to be unaffected by nonlinear averaging or antenna pattern effects. The
brightness temperature characteristics of the external targets should be stable and well-known to be used as reliable
absolute references. Calm ocean areas have been used as cold reference targets to cross-calibrate the SSM/I, TMI and AMSR-E
sensors at the cold end (80-150 K) of the typical Earth-view brightness temperature dynamic range. However, even if the cold
end of the calibration is adjusted accurately, such that ocean geophysical products can be accurately derived, the warm end
of the calibration may still be inaccurate, giving rise to inaccuracies in geophysical retrievals over land. There is less
knowledge of what constitutes a suitable target at the mid-range (~200 K) or warm end (250-300 K) of the scale. Ice sheets
have been considered for the mid-range, and tropical forests for the warm end, but there has been relatively little analysis
of the radiative transfer modeling accuracy, and spatial and temporal stability, of the brightness temperatures of ice sheet
and forest locations that might make them suitable choices as external targets for spaceborne radiometer system calibration.
We will present a systematic investigation of the brightness temperature spatial and temporal variability of a range of
ice-sheet and forest sites in an effort to characterize and select optimum sites for long-term spaceborne radiometer system
calibration monitoring over land. Such sites may be intstrumented and maintained as calibration sites for future missions
such as CMIS and Hydros.
DE: 3360 Remote sensing
DE: 1894 Instruments and techniques
DE: 1863 Snow and ice (1827)
DE: 1640 Remote sensing
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting