After analysis and consultation with the Department of Energy, NASA’s Planetary Science Division is pleased to announce that the ban on the use of Radio-isotope Power Systems (RPSs) by proposers responding to the upcoming Discovery 2018 AO has been removed. Proposers will be able to include the use of up to two (2) Multi-mission Radio-Isotope Thermal Generators (MMRTGs) to enable or significantly enhance their mission concept. Costs to be borne by proposers for the MMRTGs, the related environmental impact assessments, and the required Nuclear Launch Approval process will be announced once determined.