Sample return missions, by nature, require high levels of spacecraft autonomy. Developments in hardware avionics have led to more capable real-time onboard computing platforms, which allow for the implementation of more sophisticated algorithms. A real-time convex optimizer named COARSE (Convex Optimizer for Asteroid Rendezvous and Sampling Return) is proposed in order to efficiently guide path planning operations as well as spacecraft guidance and control. COARSE consists of a series of high level goals with specific set of execution steps, rather than complex interaction with ground control. This proposal plans to develop and simulate a basic optimizer for the purpose of a robotic spacecraft in proximity operations to an asteroid for a sample return mission, and implement in a spacecraft avionics software environment. If follow on Phase II work is awarded, the optimizer can be matured to expand higher levels of system complexity and constraints, potentially dealing with tasking multiple spacecraft working in coordination.