The National Polar-orbiting Operational Environmental Satellite System (NPOESS) spacecraft design is based on the Northrop Grumman T430 that has legacy to the Earth Observing System (EOS) Aqua and Aura. The EOS conceived and was structured to achieve cost/schedule savings over multiple builds by adhering to rigorous requirements and minimizing changes to accommodate instruments. The larger sized NPOESS bus has been enhanced to support 14 or more sensors in common locations for the 3 NPOESS orbit planes. Spacecraft deck space and other spacecraft resources such as mass, power and data accommodation have been reserved for "Instruments of Opportunity" that may be selected and inserted into the baseline mission schedule at later dates. This poster will examine the EOS lessons learned from Aqua and Aura and report on the progress of the pre-planned product improvement (P3I) payload accommodations for NPOESS.