of a New Approach to Remote Sensing of Earth’s Atmosphere

primary means of monitoring the atmosphere on a global scale is remote sensing of Earth from space, and occul-tation methods based on observing changes in a star’s spectrum as it sets through the atmosphere have proven valuable in this endeavor. Two occultation techniques—focused respectively on atmospheric extinction and refrac-tion—have been treated separately historically, but the combination of the two offers the possibility of higher accuracy, greater altitude coverage, and simultaneous measure-ment of primary and trace gases, both of which are important in the chemical balance of the atmosphere. Using data from the Ultraviolet and Visible Imagers and Spectrographic Imagers (UVISI) on the Midcourse Space Experiment (MSX) satellite, we have developed a combined extinctive/refractive stellar occultation technique that relates the changes in measured stellar intensity to the height-dependent density profiles of atmospheric con-stituents and have demonstrated its viability for retrieving both primary and trace gases through the analysis of approximately 200 stellar occultations. This self-calibrating tech-nique is broadly applicable and suitable for measurement of gases that are otherwise difficult to quantify on a global basis. In this article, we summarize the development of the technique, its validation through comparison to other measurements, and its applica-tion to the study of Earth’s overall atmosphere and lower atmosphere in particular