Observations of the cosmic microwave background (CMB) polarization and temperature anisotropy are a foundation for the standard model of cosmology. Improved measurements of the CMB anisotropy and polarization will further inform us about fundamental physics, and the history of the universe and its contents. The uncertainty on galactic foreground emissions currently limits the measurement of the CMB polarization at large angular scales.

The Atacama Cosmology Telescope (ACT) is a six-meter telescope located at an altitude of 5190 m on Cerro Toco in the Atacama Desert in Chile. The second-generation receiver on ACT, called ACTPol, began measuring the CMB polarization in 2012 at 97 and 149 GHz. The third-generation receiver upgrade, Advanced ACTPol (AdvACT, begun in 2016), has improved sensitivity and five frequency channels. In this thesis, we describe the elements of the AdvACT upgrade, present a study of the galactic foreground emissions using the data from WMAP, Planck, and the Atacama B-mode Search (ABS), and present a power-spectrum analysis of the ACTPol data.