NASA has asked the Space Studies Board (SSB) of the NRC to examine issues related to space science and technology through a series of three workshops. The first of these was held in November 2007 in conjunction with another workshop being held jointly by the SSB and ASEB to assess U.S. civil space policy broadly. Some of the workshop sessions focused more than others on issues of interest to NASA's Science Mission Directorate (SMD). This book concentrates on those sessions and presents a summary of the views of the participants on the issues that are relevant to SMD. A separate book will be prepared on the full range of issues about U.S. civil space policy discussed at the workshop.