Probing Cosmic Inflation with SPIDER, a Balloon-Borne CMB Polarimeter

The polarization of the Cosmic Microwave Background (CMB) is a powerful probe of the composition and evolution of the Universe.  Inflation, a postulated period of rapid expansion shortly after the Big Bang, would imprint a unique signature in the CMB polarization, providing a new window into the physics of the early Universe. SPIDER is a balloon-borne telescope that has been optimized to search for this inflationary signal over the course of two Antarctic flights. The first of these flights took place in 2015, and I will present an overview of flight performance and preliminary data.  I will also discuss preparations for the second flight, which is planned for December 2019.  I will conclude with a discussion of prospects for future CMB polarization measurements to probe a broad range of cosmological questions.