Software for the responsive space Trailblazer satellite

SpaceDev's Trailblazer microsatellite was selected to ride a Falcon booster in the first Operationally Responsive Space (ORS) Jumpstart mission, intended to demonstrate rapid test, integration, and launch of a spacecraft. Jumpstart was a multi-pronged effort to fly a payload on the SpaceX Falcon 1 Flight 003 mission, which launched from Kwajalein Atoll in the Marshall Islands on August 2, 2008. While the launch vehicle failed to reach orbit, Jumpstart nonetheless demonstrated capabilities that are critical for responsive space missions. The microsatellite was assembled and tested at SpaceDev's Poway, California facility in less than five months - an extraordinary feat for any aerospace company. The software design, development, and test approach was a key part of meeting this schedule. Our use of Linux as the operating system (OS) on the satellite's main processor allowed rapid development and testing because much of the software can be run and tested on PCs instead of only on the target hardware. This decoupled the software development from the hardware development. Heavy use of simulation tools allowed a wide range of testing, from high-fidelity component-level simulations to real-time hardware-in-the-loop (HWIL) system-level simulations. Where device emulators were not available or uneconomical to develop, we used ldquoin-placerdquo software emulators where the flight software on-board communicated via a high-bandwidth Ethernet ldquoback doorrdquo to an off-board real-time simulator. This paper discusses the history of the Trailblazer microsatellite program, the software architecture, and the software development process.