Mapping sodium distribution in the exosphere of Mercury with tip-tilt image stabilization

Mapping the sodium emission about Mercury is a difficult observational problem, since Mercury is seen either against the bright daytime sky, or against a dark sky at very high air masses. The distribution of sodium emission over the surface of Mercury is non-uniform, and changes over time. These effects give clues to the processes that produce the sodium and control its distribution, so that improved mapping of sodium emissions over the Mercury surface will help clarify their relative importance. We have adapted an image stabilizer utilizing a piezoelectric driven tip-tilt correction mirror for daytime spectral imaging of Mercury. The image stabilizer, which was originally developed for solar observations at the McMath–Pierce solar telescope, results in a noticeable improvement in spatial resolution of our Mercury sodium images. In this paper we give initial results from use of the tip-tilt image stabilizer for observations of Mercury’s sodium exosphere. Further systematic observations and improvements are planned for the image stabilizer system, as well as experimental observations with a low-order adaptive optics system incorporating a commercially available 37-actuator deformable mirror.