Thesis (M.S.)--University of Michigan, 1981.

Snow albedo is one of the most important factors for atmosphere-surface energy exchange in high latitude areas. Remote sensing provides continual observations of snow albedo. However, the reliability of snow albedos obtained from remotely sensed images can be problematic, especially when acquired over heterogeneous land surfaces. This research examines spatial variations in snow albedo observed under different conditions in order to assess how accurate an individual in situ observation of snow albedo is when compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow albedo product (MOD10A1) and its relationship with land surface types. In addition to the field observations, albedos retrieved from two SURFRAD stations are also examined. The overall Root Mean Square Error (RMSE) between the in situ and MODIS albedos is 8%. Semivariogram analysis of Landsat ETM+ snow albedo retrievals on January 26th, 2010 over an ice and snow covered lake indicates spatial autocorrelation lengths of approximately 260 m, suggesting limited in situ observation can be considered fairly representative of albedos retrieved from MODIS images. To further reveal what parameters could influence the spatial representativeness, this research examined landscape metrics based on seven binary snow maps created from Landsat images for three areas of differing roughness and for different snow cover conditions. There are two Landscape metrics, Mean Shape Index (MSI) and Area Weighted Shape Index (AWMSI), were found to be correlated the spatial autocorrelation lengths of snow albedo as measured from the range distance of the modeled semivariograms. In addition, this research also introduced a method of using multi-angle mast to measure the surface bidirectional reflectance distribution function (BRDF). This method could be used for further research to build the BRDF library of the snow-covered canopies.

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Very precise photometry of transiting extrasolar planets can be used to learn about the physical structure of Jupiter-like planets in an exoplanetary systems. The fraction of light reflected from the planet (albedo) provides crucial insight into the chemical structure of atmospheres and global thermal properties of a planet, including heat dissipation and global weather patterns. Measuring the albedo of an exoplanet requires very precise photometry with high time sampling and nearly continuous time coverage spanning may orbits, which can be achieved at present only from space. We present space-based photometry of the transiting exoplanetary system HD 209458 obtained with the MOST (Microvariablity and Oscillations of STars) satellite during 2004 and 2005. The data span 14 and 44 days respectively, and have nearly complete time coverage for both spans. The HD 209458 photometry was obtained in MOST's Direct Imaging mode, not part of the original mission but implemented to make possible measurements of stars in the brightness range 6.5 < V < 13. The photometric reduction techniques developed for this thesis have become the standard pipeline for processing MOST Direct Imaging data, in particular the corrections for stray Earthshine reaching the MOST instrument focal plane. Our analysis of MOST photometry of HD 209458 sets a 1 sigma upper limit on the depth of the optical eclipse of the planet of 17 parts per million (ppm) = 17 micromagnitudes. This corresponds to a 1 sigma upper limit on the flux ratio of planet to star of 1.57 x 10^-5 and an upper limit on the geometric albedo in the MOST bandpass (400 to 700 nm) of 8%. This is the most sensitive measurement of an exoplanetary albdeo ever obtained. The limit on the albedo of the gas giant HD 209458b means it much less reflective as Jupiter. This result rules out the presence of reflective clouds in the atmosphere of HD 209458b and has already enabled theoretical modeling of far-infrared measurements to contrain the planet's equilibrium atmospheric temperature to be 1550 +/- 150 K. The MOST albedo analysis demonstrates the potential of spacebased photometry missions like CoRoT (launched in December 2006) and Kepler (due for launch in early 2009) and has already provided important lessons for both missions.

Very precise photometry of transiting extrasolar planets can be used to learn about the physical structure of Jupiter-like planets in an exoplanetary systems. The fraction of light reflected from the planet (albedo) provides crucial insight into the chemical structure of atmospheres and global thermal properties of a planet, including heat dissipation and global weather patterns. Measuring the albedo of an exoplanet requires very precise photometry with high time sampling and nearly continuous time coverage spanning may orbits, which can be achieved at present only from space. We present space-based photometry of the transiting exoplanetary system HD 209458 obtained with the MOST (Microvariablity and Oscillations of STars) satellite during 2004 and 2005. The data span 14 and 44 days respectively, and have nearly complete time coverage for both spans. The HD 209458 photometry was obtained in MOST's Direct Imaging mode, not part of the original mission but implemented to make possible measurements of stars in the brightness range 6.5 < V < 13. The photometric reduction techniques developed for this thesis have become the standard pipeline for processing MOST Direct Imaging data, in particular the corrections for stray Earthshine reaching the MOST instrument focal plane. Our analysis of MOST photometry of HD 209458 sets a 1 sigma upper limit on the depth of the optical eclipse of the planet of 17 parts per million (ppm) = 17 micromagnitudes. This corresponds to a 1 sigma upper limit on the flux ratio of planet to star of 1.57 x 10^-5 and an upper limit on the geometric albedo in the MOST bandpass (400 to 700 nm) of 8%. This is the most sensitive measurement of an exoplanetary albdeo ever obtained. The limit on the albedo of the gas giant HD 209458b means it much less reflective as Jupiter. This result rules out the presence of reflective clouds in the atmosphere of HD 209458b and has already enabled theoretical modeling of far-infrared measurements to contrain the planet's equilibrium atmospheric temperature to be 1550 +/- 150 K. The MOST albedo analysis demonstrates the potential of spacebased photometry missions like CoRoT (launched in December 2006) and Kepler (due for launch in early 2009) and has already provided important lessons for both missions.

Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.Sc.). / Written for the Dept. of Atmospheric and Oceanic Sciences. Title from title page of PDF (viewed 2009/06/25). Includes bibliographical references.

Very precise photometry of transiting extrasolar planets can be used to learn about the physical structure of Jupiter-like planets in an exoplanetary systems. The fraction of light reflected from the planet (albedo) provides crucial insight into the chemical structure of atmospheres and global thermal properties of a planet, including heat dissipation and global weather patterns. Measuring the albedo of an exoplanet requires very precise photometry with high time sampling and nearly continuous time coverage spanning may orbits, which can be achieved at present only from space. We present space-based photometry of the transiting exoplanetary system HD 209458 obtained with the MOST (Microvariablity and Oscillations of STars) satellite during 2004 and 2005. The data span 14 and 44 days respectively, and have nearly complete time coverage for both spans. The HD 209458 photometry was obtained in MOST's Direct Imaging mode, not part of the original mission but implemented to make possible measurements of stars in the brightness range 6.5 < V < 13. The photometric reduction techniques developed for this thesis have become the standard pipeline for processing MOST Direct Imaging data, in particular the corrections for stray Earthshine reaching the MOST instrument focal plane. Our analysis of MOST photometry of HD 209458 sets a 1 sigma upper limit on the depth of the optical eclipse of the planet of 17 parts per million (ppm) = 17 micromagnitudes. This corresponds to a 1 sigma upper limit on the flux ratio of planet to star of 1.57 x 10^-5 and an upper limit on the geometric albedo in the MOST bandpass (400 to 700 nm) of 8%. This is the most sensitive measurement of an exoplanetary albdeo ever obtained. The limit on the albedo of the gas giant HD 209458b means it much less reflective as Jupiter. This result rules out the presence of reflective clouds in the atmosphere of HD 209458b and has already enabled theoretical modeling of far-infrared measurements to contrain the planet's equilibrium atmospheric temperature to be 1550 +/- 150 K. The MOST albedo analysis demonstrates the potential of spacebased photometry missions like CoRoT (launched in December 2006) and Kepler (due for launch in early 2009) and has already provided important lessons for both missions. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Orientador: Rubens Monti / Resumo: ---- / Mestre