  One of the current opportunities for stellar atmospheric modeling is the
interpretation of optical interferometric data of stars. Starting from the
robust, open source ATLAS atmospheric code (Kurucz, 1979), we have developed a
spherically symmetric code, SATLAS, as a new option for modeling stellar
atmospheres of low gravity stars. The SATLAS code is tested against both
interferometric observations of M giants by Wittkowski and collaborators, and
spherically symmetric M giant NextGen models from the PHOENIX code. The SATLAS
models predict interferometric visibilities that agree with the observed
visibilities and with predicted visibilities, and the SATLAS atmospheric
structures also agree with those from spherical PHOENIX models, with just small
differences in temperature and pressure at large depths in the atmospheres.
