As satellite equipment and mission operations become more costly, the drive to keep working equipment running with
less labor-power rises. Demonstrating the feasibility of autonomous satellite servicing was the main goal behind the
Orbital Express (OE) mission. Like a tow-truck delivering gas to a car on the road, the "servicing" satellite of OE had to
find the "client" from several kilometers away, connect directly to the client, and transfer fluid (or a battery)
autonomously, while on earth-orbit. The mission met 100% of its success criteria, and proved that autonomous
satellite servicing is now a reality for space operations.
Planning the satellite mission operations for OE required the ability to create a plan which could be executed
autonomously over variable conditions. As the constraints for execution could change weekly, daily, and even hourly,
the tools used create the mission execution plans needed to be flexible and adaptable to many different kinds of changes.
At the same time, the hard constraints of the plans needed to be maintained and satisfied. The Automated Scheduling and
Planning Environment (ASPEN) tool, developed at the Jet Propulsion Laboratory, was used to create the schedule of
events in each daily plan for the two satellites of the OE mission.
This paper presents an introduction to the ASPEN tool, an overview of the constraints of the OE domain, the variable
conditions that were presented within the mission, and the solution to operations that ASPEN provided. ASPEN has
been used in several other domains, including research rovers, Deep Space Network scheduling research, and in flight
operations for the NASA's Earth Observing One mission's EO1 satellite. Related work is discussed, as are the future of
ASPEN and the future of autonomous satellite servicing.