NASA’s head of human spaceflight has resigned, Politico reports. Douglas Loverro, who served as the associate administrator for the human exploration and operations mission directorate, said in a letter to NASA employees that he was leaving due to a “mistake” and “with a very, very heavy heart.” Loverro wrote that he had misjudged an unspecified risk that he must bear the consequences of: “My leaving is because of my personal actions, not anything we accomplished together.” His resignation, just seven months into his tenure, comes ahead of the planned May 27 launch of a manned spaceflight from U.S. soil for the first time since 2011.