ACCESS: the Arizona-CfA-Catolica-Carnegie Exoplanet Spectroscopy Survey

Transmission spectroscopy provides a powerful tool to study the atmospheric properties of exoplanets. Optical transmission spectra are particularly important, since they provide the spectral baselines for clear, cloudy, and hazy atmospheres needed to correctly interpret infrared transmission spectra observed with HST and the upcoming JWST. For 6 years the Arizona-CfA-Católica-Carnegie Exoplanet Spectroscopy Survey (ACCESS) has been observing and analyzing the atmospheres of over a dozen planets, ranging from hot Jupiters to super-Earths. These observations have been collected with IMACS mounted on the 6.5-m Magellan telescope with a homogeneous setup designed for measurements from 0.4-0.9 microns. The homogeneity of ACCESS's data is extremely important because it allows for minimization of systematic differences between instruments and better optimization of data analysis techniques. This dataset has allowed us to study 1) how stellar heterogeneities can masquerade as atmospheric features and some methods to correct for such effects, 2) optimal detrending algorithms that produce the highest accuracy and precision, 3) observing techniques with ACCESS's telescopes that produce the greatest scientific yield, and more. We give an overview of the status of the survey and summarize the main findings from our published studies. We also describe the expansion of ACCESS to the northern hemisphere with the new BINOSPEC spectrograph on the 6.5-m MMT and our plans to start characterizing the atmospheres of transiting planets discovered by TESS.