Development of a Modular Command and Data Handling Architecture for the KySat-2 CubeSat

KySat-2 is a IV CubeSat launched on the NASA ELaNa IV mission on November 19, 2013. The Command & Data Handling (C&DH) architecture for KySat-2 leverages aspects of the Space Plug-and Play Avionics (SPA) standard developed by the Air Force Research Laboratory (AFRL) and adapts it to the constraints of the CubeSat form factor. The design eases interfacing commercial-off-the-shelf (COTS) and legacy components in the satellite and also enhances software reusability, with motivation to decrease time-to-orbit and reduce system cost and complexity, while increasing reliability. The KySat-2 CubeSat C&DH architecture utilizes a central processor that carries out mission-specific functionality, command interpretation, and scheduling. Interface processors are dedicated to, and all processors communicate on a shared I2C bus. This distributed processing architecture provides a level of abstraction between the mission-specific functionality and the more general purpose features of satellite subsystems, enabling increased reuse of non-mission specific hardware and software. This paper describes the distributed architecture of the KySat-2 C&DH, as well as the advantages and challenges of the distributed approach.