Imaging experiments to detect an extended sodium atmosphere on the moon

Abstract

Wide angle, low light level imaging observations of the lunar sodium atmosphere have been conducted from McDonald Observatory, Texas. Three imaging techniques have been tried: field of view offset, shadow mask, and coronagraph mask. Initial observations in February, 1991, were successful using the field of view offset technique. These observations showed a comet-like distribution of sodium consisting of a bright coma extending to 5 lunar radii (R M) on the sunward side and a tail feature detectable to 15 to 20 R M on the antisunward side. The dayside radial intensity decrease is well fit by a power law of index −4. Subsequent coronagraph mask observations in September–October, 1991, showed similar overall intensities, a shorter tail feature, and significant solar zenith angle behavior in the dayside intensities.