Utilizing Electric Propulsion by

The Energetic Transient Array (ETA) is a mission, proposed by the Center for Space Research (CSR) at MIT, to set up an interplanetary constellation of six microsatellites for Gamma Ray Burst (GRB) astrometry. The microsatellites will be deployed into distinct heliocentric orbits by a carrier spacecraft which will be propelled by a stationary plasma (SPT-70) electric thruster. This thesis documents the analysis carried out for the ETA constellation design. It addresses ETA system design from the systems engineering standpoint, with emphasis on constellation and propulsion system issues. Beginning with scientific requirements, the most important of which is GRB localization accuracy, systems engineering tools are applied to define trade options, system requirements, architecture and interfaces. Require-ments flowdown to the constellation level enables an assessment of propulsion options through a top level trade study. This has resulted in the selection of the SPT-70 propulsion system for the carrier spacecraft. Constellation analysis, consisting of trade studies, includes consideration of design aspects such as number of microsatellites, SPT-70 thrust