LEGS: build Earth’s next links to lunar missions

Lunar Exploration Ground Sites, or LEGS, is NASA’s effort to expand direct-to-Earth communications capacity through a geographically distributed ground network. It adds capacity to the Near Space Network for missions beyond geostationary distances, including lunar exploration. The system is on Earth: despite the name, these are not landing sites on the Moon. More lunar missions create demand for antenna time, compatible equipment and reliable delivery of their data.

NASA’s September 2026 program page shows the first LEGS antenna installed at White Sands Complex in New Mexico. The agency also describes a planned industry solicitation and selection by 2027. Meanwhile, SANSA’s July 2026 Matjiesfontein update reports continuing construction and an eighteen-to-twenty-four-month completion forecast. These are dated development milestones. An installed dish, an announced procurement and an accepted operational service answer different questions about readiness.

Earth’s rotation carries a station toward and away from a target’s direction. Separated sites can take over contacts as local visibility changes, provided their equipment and schedules support the mission. This is a different problem from a spacecraft passing behind the Moon. If the Moon blocks the path to Earth, simply choosing another Earth station cannot create a direct line through solid rock. A suitably placed relay or a planned communication gap addresses that separate geometry.

Artemis I illustrates why names and roles matter: NASA’s Near Space Network supported early mission phases, and the Deep Space Network handled the main lunar-orbit communications. That flight’s success should not be relabeled as proof that the later LEGS network was already operating. Ground stations, spacecraft relays and shared communication standards are complementary parts of an architecture. A mission team must specify which path it needs at each phase.

Consider an invented contact with a channel rate of 400 kilobits per second lasting 300 seconds. The gross capacity is 120 megabits. If framing, coding and other overhead leave eighty percent for the useful payload, the useful capacity is 96 megabits, or 12 decimal megabytes. Those assumptions describe this exercise, not a published LEGS performance specification. A mission generating more than that amount between contacts needs another opportunity, a changed data plan or more effective delivery capacity.

Geometric visibility alone does not guarantee a booked, working contact. Operations must coordinate schedules, compatible radio modes, pointing, timing and the onward data route. Commissioning tests the complete path, including what happens after an interruption. The developing network therefore combines physical infrastructure with service agreements and operational work. A useful assessment asks both whether a station can see the mission and whether it can deliver the required information under the agreed conditions.

From channel capacity to useful information