The PRoject for OnBoard Autonomy (PROBA) missions are a series of microsatellites launched by the European Space Agency (ESA) and intended to provide an in-orbit test platform for new technologies. The second satellite in the series, PROBA2, was launched on November 2, 2009. The primary mission goal of PROBA2 is to perform an in-flight demonstration of a series of new spacecraft technologies. The secondary mission goal is the exploitation of the payload of scientific instruments consisting of two Sun-sensing instruments, the Sun Watcher with Active Pixel Sensor and Image Processing, and the Large Yield Radiometer. Both instruments are unique in a technological sense but also provide unique scientific data for the solar physics community. In this volume, a number of papers are collected that give an overview of the mission, the spacecraft, its instrument and its operations. In addition, the scientific outcome of the mission during the first two years is presented in a series of research papers.  This volume is aimed at graduate students and researchers active in solar physics and space science. Previously published in Solar Physics journal, Vol. 286, No. 1, 2013.