Light High-Orbit Utility Signal Emitter (LightHOUSE) is a proposed small satellite constellation designed by researchers at MIT Lincoln Laboratory to help overcome limitations in cislunar space, addressing severe positioning bottlenecks caused by Earth-bound systems like NASA’s Deep Space Network (DSN). According to Aaron Greenberg of the laboratory’s Laser Communications Group, spacecraft in cislunar regions face limited support resources while operating in an area that is reemerging as a strategic priority for national security.
The Cislunar Navigation Bottleneck and Deep Space Network Limits
Earth-based navigation relies heavily on global positioning satellites, making positioning processes almost invisible to terrestrial users. Beyond geosynchronous Earth orbit, however, spacecraft do not have that kind of always-available positioning service, according to laboratory analyses. Numerous international and multi-mission endeavors currently rely upon NASA’s Deep Space Network (DSN), which functions as a precise yet constrained terrestrial collection of radio antennas.
Because all DSN sites are located on Earth, their separation is small compared with the scale of cislunar space. This tight separation limits the angular baselines available for orbit determination. Calculating the exact trajectories of far-off spacecraft can demand hours of work, and DSN accommodates only a limited handful of missions simultaneously. Furthermore, unlike GPS, which passively sends data for users to receive, DSN requires user spacecraft to actively emit signals for measurement.
Did you know? While the operating budget of GPS is $1.8 billion per year, a single DSN dish costs roughly $85-100 million.
How the LightHOUSE Optical Beacon Constellation Works
To bypass terrestrial radio constraints, researchers in the Laser Communications Group and Advanced Capabilities and Technologies Group are developing LightHOUSE. According to the project team, the concept would use a small constellation of satellites in high-altitude orbits as cooperative optical beacons.
To determine each spacecraft’s velocity and three-dimensional location, these beacons would utilize stellar background imaging alongside exchanged communication and timing signals with target vehicles. Timothy Yarnall, an associate leader of the Laser Communications Group, states that the concept hinges on a cooperative ranging capability enabled by free-space optical communications. The underlying framework builds upon laboratory achievements previously validated through NASA-backed initiatives including TBIRD and O2O, alongside the Optical Time Transfer for Resilient Satellite Communications Networks project, which was spearheaded by the Laser Communications Group with backing from the lab’s internal R&D allocations for optical systems technology.
Overcoming Engineering Hurdles and System Asymmetry
Placing beacons in ultrahigh orbits, up to roughly 1 million miles in altitude, replicates the angular diversity of GPS signals for users across cislunar volumes. These elevated vantage points likewise facilitate direct contact with vehicles positioned on the moon’s far hemisphere relative to Earth, thereby avoiding communication gaps comparable to the 40-minute period when Artemis II passed behind the moon.
LightHOUSE borrows from the GPS philosophy, designed to place most of the technical burden on the beacon satellites, rather than on user spacecraft. Seth Trotz, a senior staff member in the Advanced Capabilities and Technologies Group, notes that a major challenge will be making these services as easily accessible as possible to all potential users, with designed systems being highly asymmetric. LightHOUSE beacons carry telescopes with tens-of-centimeter diameters and laser transmitters in the tens-of-watts range, whereas users would need only centimeter-scale apertures and tens-of-milliwatt lasers.
Future Outlook and Development Timeline
The research team is currently refining the system concept through analysis, simulation, and laboratory experimentation. In the near term, engineers plan to publish a detailed architecture for providing navigation data to LightHOUSE users. To foster Artemis and subsequent cislunar exploratory efforts, the ultimate objective is ensuring that navigation past geosynchronous altitudes becomes dependable, standard, and widely attainable for various operators.
This initiative receives backing from the undersecretary of war for research and engineering via the division’s internal research and development budget dedicated to sensing and communications. Deploying a comprehensive operational network demands heavy financial backing, with expenditures potentially reaching hundreds of millions of dollars.
Frequently Asked Questions
What is LightHOUSE?
LightHOUSE is a concept called the Light High-Orbit Utility Signal Emitter developed by researchers at MIT Lincoln Laboratory.
Why can’t spacecraft in cislunar space just use GPS?
Spacecraft traveling through the space between Earth and the moon lack access to standard, continuous navigation services, forcing missions to depend on terrestrial alternatives like the Deep Space Network.
How does LightHOUSE differ from traditional radio systems?
Rather than depending exclusively on radio-frequency technology, LightHOUSE would leverage free-space optical communications via spatial laser links, transferring the primary engineering demands onto the beacon satellites.
Explore More: Want to stay updated on deep space communications and aerospace engineering breakthroughs? Subscribe to our newsletter or browse our archives for the latest reports from MIT Lincoln Laboratory and NASA missions.
Related reading