Harvard faculty are active in observational cosmology, with interests including the study of inflation, dark energy, dark matter, and the large-scale structure of the Universe. Professors Kirshner and Stubbs lead groups using Type Ia supernovae to measure the acceleration of the expansion rate of the Universe. Professor Eisenstein is director of the Sloan Digital Sky Survey III and is an expert in the use of galaxy clustering to measure the cosmic distance scale with the baryon acoustic oscillation method. Professor Stubbs pursues dark energy by measuring the abundance of clusters detected in the Sunyaev-Zel'dovich effect with the South Pole Telescope. Professor Kovac builds state-of-the-art experiments to search for gravitational waves from inflation using cosmic microwave background polarization measured by telescopes sited at the South Pole. Professor Finkbeiner searches for dark matter annihilation signatures in the gamma-ray and microwave sky. Dr. Alexey Vikhlinin is an expert on cluster of galaxies. His group pioneered studies of dark energy with observations of the evolving cluster mass function. Dr. Vikhlinin leads several prominent long-term observing programs with the Chandra X-ray Observatory. In addition to using CfA telescope facilities, the CfA is a member of the PanStarrs survey, Sloan Digital Sky Survey III, BICEP-II, SPUD, and Polar collaborations, and the Murchison Wide Field Array. The CfA observational cosmology programs work in close collaborations with the Institute for Theory and Computation to build a close bond between theory and observation.