NASA has just announced the selection of ARM Option B – the alternative ARM mission to pluck a boulder off a larger NEA and return it to the vicinity of the Moon. The rock could be up to 4m in size. Launch is planned for 2020. The estimated costs are slightly larger than Option A, but since this mission involves studying a larger asteroid target (with a stay there of up to 400 days), it is more applicable to a variety of NASA interests, including testing the gravity tractor for planetary defense. The next steps in this mission are a Phase A study, and specific decisions that need to be made this year on defining the solar electric propulsion system. Three NEAs are currently considered potential targets.
