Revolutionary design meets spacecraft reality: Lessons learned in developing a PnPSat power system

The Plug and Play Satellite (PnPSat) Program, initiated by the Air Force Research Laboratory in Albuquerque, is both a testbed for innovative spacecraft components and integration concepts, and a fully functional spacecraft with the first Flight Unit rapidly approaching flight readiness. While the intent of the PnPSat Program is to prove out technologies and implement processes that allow rapid integration and test of flight-ready units, the integration of the first PnPSat flight article has not been without some more traditional platform integration challenges. Design_Net Engineering (D_Net) has been tasked with supplying both hardware and systems expertise to develop most of the Power Subsystem components for PnPSat. We have successfully developed, delivered and integrated a Solar Array Controller (SAC) and an Energy Storage Module (ESM) that provide the hardware and software interfaces necessary to effectively enable solar power acquisition and management on the PnPSat spacecraft. The lessons learned along the path to successful integration and test will be of value to anyone else developing hardware and firmware destined for the PnPSat architecture. The PnPSat program paradigm is based on a readily available collection of hardware components and their associated embedded software interfaces (on-shelf ldquoat the depotrdquo) that can be assembled in a variety of configurations on a standard spacecraft structure, providing a fully configured and tested, flight ready spacecraft within a matter of days following call-up. The principal challenge facing the Power Subsystem developer under these unique design constraints is to deliver a system that does not simply meet a point design spec, but rather one that includes component modules capable of supporting a wide range of future mission requirements, while also fitting the form factor and interface architecture dictated by the need for component relocateability, and while capable of reliable operation in such a distri- buted power architecture. Design_Net´s hardware implementations satisfy all functional and performance requirements imposed by all projected PnPSat mission needs, while maintaining the ability to be placed anywhere on or in the spacecraft.