[show abstract][hide abstract] ABSTRACT: The top-of-atmosphere (TOA) path radiance generated by an aerosol mixture can be synthesized by linearly adding the contributions of the individual aerosol components, weighted by their fractional optical depths. The method, known as linear mixing, is exact in the single-scattering limit. When multiple scattering is significant, the method reproduces the atmospheric path radiance of the mixture with less than 3% errors for weakly absorbing aerosols up to optical thickness of 0.5. However, when strongly absorbing aerosols are included in the mixture, the errors are much larger. This is due to neglecting the effect of multiple interactions between the aerosol components, especially when the values of the single-scattering albedos of these components are so different that the parameter e = the sum of f(sub i)[(bar)omega(sub i) - (bar)omega(sub mix)]/(bar)omega(sub i) is larger than approximately 0.1, where (bar)omega(sub i)and f(sub i) are the single-scattering albedo and the fractional abundance of the ith component, and (bar)omega(sub mix) is the effective single-scattering albedo of the Mixture. We describe an empirical, modified linear-mixing method which effectively accounts for the multiple interactions between aerosol components. The modified and standard methods are identical when epsilon = 0.0 and give similar results when epsilon is less than or equal to 0.05. For optical depths larger than approximately 0.5, or when epsilon is greater than 0.05, only the modified method can reproduce the radiances within 5% error for common aerosol types up to optical thickness of 2.0. Because this method facilitates efficient and accurate atmospheric path radiance calculations for mixtures of a wide variety of aerosol types, it will be used as part of the aerosol retrieval methodology for the Earth Observing System (EOS) multiangle imaging spectroradiometer (MISR), scheduled for launch into polar orbit in 1998.
Journal of Geophysical Research 08/1997; 102:16883-16888. · 3.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Multi-angle Imaging SpectroRadiometer (MISR) instrument is
currently under development at JPL for the AM1 spacecraft in the Earth
Observing System (EOS) series. MISR consists of nine pushbroom cameras,
and will provide global coverage in four visible/near-infrared spectral
bands. This measurement strategy provides systematic multi-angle imagery
of the Earth for studies of aerosols, surface radiation, and clouds. An
on-board calibrator consisting of deployable solar diffusers and a set
of stable photodiodes provides a high-accuracy detector-based
calibration. In this paper the authors report on the progress of the
instrument fabrication and testing and focus on the application of
MISR's unique observational strategy to studies of tropospheric aerosols
Geoscience and Remote Sensing Symposium, 1995. IGARSS '95. 'Quantitative Remote Sensing for Science and Applications', International; 08/1995
[show abstract][hide abstract] ABSTRACT: Distributions of temperature dust, vapors, and condensates measured. Report describes design and intended uses of developmental pressure-modulator infrared readimeter, PMIRR, carried aboard Mars Observer spacecraft. Applies remote-sensing techniques used to study atmosphere of Earth. Takes similar measurements from polar orbit around Mars. Nine-channel atmospheric sounder that employs filter and pressure-modulation gas-correlation infrared radiometry.
[show abstract][hide abstract] ABSTRACT: The study of the atmosphere and climate of Mars will soon be advanced considerably by the Mars Observer mission. This paper describes the atmospheric sounder for this mission and how it will measure key Martian atmospheric parameters using IR gas correlation and filter radiometry. The instrument now under development will provide high-resolution vertical profiles of atmospheric temperature, pressure, water vapor, dust, and clouds using limb sounding techniques as well as nadir observations of surface thermal properties and polar radiative balance.