SOC-i: A CubeSat Demonstration of Optimization-Based Real-Time Constrained Attitude Control

The Satellite for Optimal Control and Imaging (SOC-i) is a 2U CubeSat that will fly the first in-space demonstration of real-time optimization-based constrained attitude control. SOC-i is developed by AACT, a student team at the University of Washington (UW), and consists of two payloads and several supporting subsystems. The primary payload is a convex optimization-based attitude guidance algorithm called SOC-i's Optimal Attitude Reorientation (SOAR). SOAR will be the first software of its kind tested on an orbiting spacecraft. The secondary payload is a CMOS camera that serves as an instrument to demonstrate SOC-i's pointing abilities. Though SOC-i is a CubeSat flight demonstration of the SOAR technology, it is relevant for spacecraft missions of all types given the prevalence of sun sensor-based attitude estimation, the need for sun-sensitive instrumentation in space, the finite control authority of all actuators, and the desire to execute rotations while minimizing some performance metric (e.g., electrical power). A small satellite mission is an ideal proving ground for SOAR. To reduce mission risk, SOC-i leverages COTS components from standard CubeSat suppliers; the power management system, battery, solar arrays, antenna, and actuators all have flight heritage, while the chassis and onboard computer are custom built by UW students. The design and development of these subsystems is presented in detail.