Developing the process tools and software architecture for the PnPSat initiative

Over the past few years, the Air Force Research Laboratories in Albuquerque, New Mexico have been leading the charge to establish a new paradigm for the satellite development process. Central to this development is the Space Plug&play Avionics (SPA) standards, which define standard electrical, data, and mechanical interfaces for all components that are used to construct the system. "Components" consist of both hardware and software elements, all capable of being integrated and tested rapidly to create functional capability. It is envisioned that with the diligence being applied, it will ultimately be possible to draw from stock items at a depot to design, assemble, and launch a satellite in a matter of days. An essential enabling aspect of the process is a collection of highly interoperable software modules, conforming to the data portion of the SPA standards, which can be selected from a library based upon their ability to collectively meet a set of prescribed mission objectives. If properly constructed, the modules can self-configure on the data network - ideally without human intervention or modification(12). Abolishing the segment of the satellite life cycle associated with the development of flight software is one of the most critical goals to achieve if the "six-day-satellite" concept is to become reality. Design-Net Engineering has been active in the refinement of these standards, as well as a primary contributor to the development of a flight software architecture to validate the approach. We have also created a development environment that takes advantage of the network-based data standards to allow code to be written and tested without physical hardware. This capability, termed Flight Software In the Loop (FSWIL), utilizes a robust simulation framework to present behavioral models of hardware devices to the software developer that are indistinguishable from the actual articles. The PnPSat program is an initiative that has been established by AFRL to serve as a technology demonstration for the SPA standards. Due to the fact that many of the core technologies were being matured in parallel, it became necessary to develop the FSWIL capability to allow software efforts to progress without a supporting hardware infrastructure. The tools have important implications for the community beyond PnPSat however, as they allow developers to write and test code (or hypothetical hardware models) remotely before installing new capability in the Responsive Space Testbed (the home of the SPA initiative). This paper will describe the FSWIL tool as well as the SPA-based flight software architecture and implementation products that support the PnPSat program.