SMAP Observatory concept - A configuration of compromises

SMAP (Soil Moisture Active and Passive) is a proposed scientific mission that would provide global mapping of Earth soil moisture and freeze/thaw state. The proposed SMAP Observatory would accommodate two primary Instruments - L-band (1.26 GHz) Radar and L-band (1.4 GHz) Radiometer on one spacecraft. Both instruments would share a 14.6 RPM spinning Antenna System with a 6m diameter deployable Reflector and a common RF Feed. The key challenge for the Observatory configuration is in meeting the needs of the science and the supporting subsystems (many of which have stringent demands as well) and ensuring that the spacecraft could meet all operational, pointing, environmental, and launch vehicle requirements. This paper describes the continuing evolution of the proposed SMAP Observatory configuration, the challenges of balancing the conflicting requirements, and the major configuration driving decisions and compromises.