As missions to low Earth orbit become more frequent, space traffic coordination remains a key element to efficiently operating in space. Different satellite operators using autonomous systems need to operate together and manage increasing workloads. NASA’s Starling spacecraft swarm recently tested a coordination with SpaceX’s Starlink constellation, demonstrating a potential solution to enhance space traffic coordination.
Led by the Small Spacecraft Technology program at NASA’s Ames Research Center in California’s Silicon Valley, Starling originally set out to demonstrate autonomous planning and execution of orbital maneuvers with the mission’s four small spacecraft. After achieving its primary objectives, the Starling mission expanded to become Starling 1.5, an experiment to demonstrate maneuvers between the Starling swarm and SpaceX’s Starlink satellites, which also maneuver autonomously.
Coordination in Low Earth Orbit
Current space traffic coordination systems screen trajectories of spacecraft and objects in space and alert operators on the ground of potential conjunctions, which occur when two objects exceed an operator’s tolerance for a close approach along their orbital paths. Spacecraft operators can request notification at a range of probabilities, often anywhere from a 1 in 10,000 likelihood of a collision to 1 in 1,000,000 or lower.
Conjunction mitigation between satellite operators requires manual coordination through calls or emails on the ground. An operator may receive a notification for a number of reasons including recently maneuvering their satellite, nearby space debris, or if another satellite adjusts its orbit.
Once an operator is aware of a potential conjunction, they must work together with other operators to reduce the probability of a collision. This can result in time-consuming calls or emails between ground operations teams with different approaches to safe operations. It also means maneuvers may require several days to plan and implement. This timeline can be challenging for missions that require quick adjustments to capture important data.
“Occasionally, we’ll do a maneuver that we find out wasn’t necessary if we could have waited before making a decision. Sometimes you can’t wait three days to reposition and observe. Being able to react within a few hours can make new satellite observations possible,” said Nathan Benz, project manager of Starling 1.5 at NASA Ames.
Improving Coordination for Autonomous Maneuvering
The first step in improving coordination was to develop a reliable way to signal maneuver responsibility between operators. “Usually, SpaceX takes the responsibility to move out of the way when another operator shares their predicted trajectory information,” said Benz.
SpaceX and NASA collaborated to design a conjunction screening service, which SpaceX then implemented. Satellite operators can submit trajectories and receive conjunction data quickly, then accept responsibility to maneuver away from a potential conjunction.
“For this experiment, NASA’s Starling accepted responsibility to move using the screening service, successfully tested our system’s performance, then autonomously planned and executed the maneuver for the NASA Starling satellite, resolving a close approach with a Starlink satellite,” said Benz.
Through NASA’s Starling 1.5 experiment, the agency helped validate SpaceX’s Starlink screening service. The Office of Space Commerce within the U.S. Department of Commerce also worked with SpaceX to understand and assess the Starlink screening service.
Quicker Response to Changes on Earth
The time it takes to plan maneuvers in today’s orbital traffic environment limits the number of satellites a human operator can manage and their ability to collect data or serve customers.
“A fully automated system that is flexible and adaptable between satellite constellations is ideal for an environment of multiple satellite operators, all of whom have differing criteria for mitigating collision risks,” said Lauri Newman, program officer for NASA’s Conjunction Assessment Risk Analysis program at the agency’s headquarters in Washington.
Reducing the time necessary to plan maneuvers could open up a new class of missions, where quick responses to changes in space or on Earth’s surface are possible. Satellites capable of making quicker movements could adjust their orbital position to capture a natural disaster from above, or respond to one swarm member’s interesting observations, moving to provide a more thorough look.
“With improved access and use of low Earth orbit and the necessity to provide a more advanced space traffic coordination system, Starling 1.5 is providing critical data. Starling 1.5 is the result of a successful partnership between NASA, the Department of Commerce, and SpaceX, maturing technology to solve such challenges,” said Roger Hunter, program manager of the Small Spacecraft Technology program. “We look forward to the sustained impact of the Starling technologies as they continue demonstrating advancements in spacecraft coordination, cooperation, and autonomy.”
NASA Ames leads the Starling projects. NASA’s Small Spacecraft Technology program within the Space Technology Mission Directorate funds and manages the Starling mission.
