Theoretical Evaluation of Vertically Viewing and Earth-Limb Scanning Modes for Rocketborne Earth-Limb Measurements.

Abstract : An optically-thin atmospheric volume emission rate profile is modeled with a series of gaussian layers; the instrument response is calculated for each mode assuming a hypothetically ideal instrument. The earth-limb scanning mode is demonstrated to have the greater sensitivity to details in the gaussian atmosphere. Limitations imposed by viewing weak layers in the presence of strong layers are considered. The question of spatial resolution is investigated by repeating the earth-limb calculations with various nonzero, infinite rejection, fields of view. The question of spatial purity is investigated by calculating the equivalent on-axis radiance resulting from the earth as an off-axis source for the HRC high rejection telescope and a hypothetical nine-order telescope. It is found that either telescope is more than adequate when used to view relatively bright optically thick emission species, and that both are limited by earth radiations when viewing optically thin atmospheric emission species.