The NPOESS program was significantly re-scoped in June 2006 as part of the Nunn-McCurdy Certification process. As a result, instruments primarily used for climate observations were de-manifested or reduced in capability – either through instrument downsizing or through elimination of flight in one or more orbits. Once certification was approved, NOAA and NASA began a formal study of options to mitigate the losses and provide the resources needed to address the agencies' future climate program goals – both in space measurements and climate product generation. Options for space measurements included the remanifestation of sensors back onto NPOESS satellites, development of new satellite missions outside of the NPOESS structure, and partnerships with foreign space agencies. In this paper, we discuss the study approach, the options considered and their relative merits. We also describe the differences between the space observations and the climate data records needed to address key uncertainties as identified in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (2007).