The Cosmology Large Angular Scale Surveyor

The Cosmology Large Angular Scale Surveyor (CLASS) is a four-telescope Cosmic Microwave Background (CMB) polarization survey, operating from high in the Andes mountains of northern Chile. Polarization in the CMB is generated by the dynamics in the early universe, and encodes information about key events in its history. By observing the E and B mode polarization patterns, CLASS can characterize cosmic inflation and explore reionization. Particularly interesting aspects of these cosmological signals — especially in the polarization pattern due to reionization — can only be seen by looking across much of the sky, which is why CLASS is optimized for large angular scale (greater than ten degrees) observation. Moreover, CLASS is unique in its approach and ability to accomplish this large angular scale measurement from the ground. The first CLASS instrument began observing in 2016, and the fourth will be deployed in the coming year. I will give an update on the survey and discuss our recent two-year observations publications, which demonstrate the effectiveness of the CLASS strategy.