GPS Technology on the Moon, Ensuring Astronauts Don’t Get Lost

A number of countries and technology companies are stepping up efforts to launch the first satellite navigation system on the moon to support many missions there.

“You have arrived at your destination.” This is a phrase that is often heard when using map navigation assistance. But what if your destination is beyond Earth? Can a system like the Global Positioning System (GPS) be extended to planets other than Earth?

Now that is about to happen. NASA and its partners in Europe and Japan are developing a concept for satellite navigation on the moon that will soon be launched. In July, the China National Space Administration (CNSA) announced its plan to build a constellation of 21 communication and navigation satellites to support their ambitions on the moon.

This push comes along with a surge in activity and exploration planned for the next few years. These missions require sophisticated logistics systems, including the positioning, navigation, and timing (PNT) systems that underlie infrastructure on Earth.

The NASA-led Artemis program, for example, aims to send astronauts to the moon’s south pole, and requires reliable communications and precise location services. China also plans to send crews to the moon this decade, while other government and private entities are also planning to send robotic explorers to the lunar surface.

The commercial space sector is also looking for opportunities in the new lunar economy, such as resource extraction, low-gravity manufacturing, scientific research, or tourism. Past lunar missions have relied on basic relays to communicate and navigate, but future lunar exploration will require a satellite system capable of covering the entire lunar surface—or at least part of it.

“GPS has been the backbone of our economy on Earth,” said Cheryl Gramling, an aerospace engineer who led the development of PNT and lunar standards at NASA, as reported by Wired, Saturday (7/9/2024).

A lunar satellite navigation system would be especially helpful in landing systems, resource utilization, and path planning. The initial focus will be on the lunar south pole because of the missions planned there. However, coverage of the entire lunar surface may be a longer-term goal.

A few complex challenges must be overcome first to ensure a lunar GPS system works. One is determining the correct time on the moon. Lunar missions have historically taken into account a two-week day and night cycle, but there is currently no standard lunar time scale similar to Coordinated Universal Time (UTC) on Earth.

Precision time is a core innovation that has enabled the emergence of global navigation satellite systems (GNSS), a category that includes the US GPS, China’s BeiDou, Russia’s GLONASS and Europe’s Galileo. The satellites in this network carry atomic clocks that measure time with extremely high accuracy. However, lunar clocks tick faster than those on Earth due to the effects of general relativity.

NASA, the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) are currently overseeing projects related to a lunar GPS constellation. These are designed to comply with an interoperability framework called LunaNet, which defines standards that will be used for communications, positioning, navigation and timing services on the moon.

Meanwhile, China is also interested in developing lunar navigation infrastructure and may develop its own lunar GPS constellation. International collaboration could be a more efficient and beneficial path for all parties. However, whether the moon will have multiple GPS systems like on Earth, or whether there will be one universal system, is still uncertain.