Dashboard keeps tabs on cislunar space
It’s not yet a mob scene, but cislunar space — the region of space between the Earth and the Moon — is going to get crowded as private companies and nations launch more and more satellites for commercial, research and military purposes. And unlike the already heavily navigated near-Earth orbital region, cislunar space is relatively unexplored and more unruly, with unique spacecraft trajectories that differ from familiar low-Earth and geostationary orbits.
That’s why Purdue University is working with Rhea Space Activity (RSA) on a U.S. Air Force contract to develop software that can monitor and predict these trajectories — essentially, a space dashboard, a 3D space situational awareness portal to track objects and analyze data.
Hsu Lo Distinguished Professor of Aeronautics and Astronautics Kathleen Howell and AAE Associate Professor Carolin Frueh are co-principal Investigators in the research. Howell is focused on the orbital characteristics needed to generate the new trajectories. Frueh is investigating how to set the first ground rules for establishing surveillance in the cislunar region; how to identify particular points of interest and observe them regularly; and how spacecraft activities can be recognized.
“I am considering all the various trajectories for vehicles and natural objects and the potential to link them together,” Howell said. It’s not a trivial task in the vastness that is cislunar space. “It may not be realistic to survey the entire sphere continuously. We also must incorporate the actions that may be taking place in Earth-Moon space — perhaps the Earth needs protection from asteroid collisions, at the same time that we are returning humans to the Moon.”
That gets complex with the dynamics of the region. Cislunar space is further from Earth than the near-Earth geosynchronous orbital region — a singular location 22,236 miles above the Earth, where spacecraft have an orbital period equal to the Earth’s rotational period. They therefore appear motionless, in a fixed position in the sky.
In contrast, the United States Space Force, in a Memorandum of Understanding with NASA, indicated that it considers its sphere of influence for surveillance and space domain awareness to extend to 272,000 miles and beyond — a more than tenfold increase in range and 1,000-fold expansion in service volume, and where orbits may not be so repeatable and predictable.
Spacecraft motion out there is governed by the gravity of the Earth and Moon simultaneously — a so-called 3-body problem.
“This means that, to monitor the spacecraft activities, differing dynamics must be taken into account,” Frueh said. “Many of the techniques which are better established in the near-Earth space still have to be developed for this very different region.”
For Frueh, that means starting from a clean sheet.
“In my group, we are self-developing all computational tools,” Frueh said. “We are using digital twins of observational systems, astrodynamics, and information-theoretic approaches.”
The project is still in its early stages in terms of the final look of the dashboard; the Purdue researchers are working with Saber Astronautics to populate the information console for monitoring and surveilling cislunar space.
“At the moment, we have developed some initial trajectories that are embedded in the visualization tool,” Frueh said. “We are currently providing expertise on what kinds of data the most useful visualizations would require.”
That data and visualization will be crucial — as will Purdue know-how. Howell’s ongoing research interests at AAE include trajectory design, mission planning, and on-orbit operations. Frueh’s research centers on space domain and situational awareness and space traffic management.
“More and more missions are being launched into cislunar space, and the traffic there will increase significantly in the near future,” Frueh said. “Its dynamic properties allow for interaction and interference with the near-Earth region, with respect to the trajectories that connect near-Earth space with the near-lunar region, as Prof. Howell has indicated. The region is large, and at the moment we have no awareness of the space activity or space debris.”
That’s crucial, said Howell, as there are many varied activities imagined for this region of space; the Moon is a current focus.
“We are not used to operating in this region continuously, so the infrastructure is not present,” she said. “The commercial sector wants to build a presence in the vicinity of the Moon and other parts of cislunar space, and will need infrastructure to enable operations, including power, communications, supply of propellant, servicing, etc. This project is an initial step to support all sectors — military, civilian and commercial.”