Abstract

Radial velocity and transit surveys have revealed a large and diverse population of exoplanets in our galaxy. To truly understand their diversity we need to obtain spectra of their atmospheres in order to probe their compositions and understand the dominant physical processes. Transiting planets allow such measurements via transmission and eclipse spectroscopy, which has been a very active field of research over the last decade. However, both space and ground-based observations present significant challenges, as none of the instruments commonly used were designed with the required level of precision and stability in mind. Here, I will discuss the observations and data analysis required to extract transmission spectra, and the resulting difficulties in obtaining robust spectra of exoplanets. I will present results of a campaign to obtain the first complete UV to NIR transmission spectra of the hot Jupiter HD 189733b, and efforts to obtain ground based transmission spectra using differential spectrophotometry.