An artist’s impression of a Moon exploration scenario. (Image: ESA)
As there are several missions to the moon planned within the next decade, space agencies have started to consider how to keep time on the moon. To address time concerns, the LunaNet architecture, designed for lunar communications and navigation services, was introduced at the ESTEC technology center of the European Space Agency (ESA) in the Netherlands in November 2022.
“LunaNet is a framework of mutually agreed-upon standards, protocols and interface requirements allowing future lunar missions to work together, conceptually similar to what we did on Earth for joint use of GPS and Galileo,” said Javier Ventura-Trav
eset, ESA’s Moonlight navigation manager, coordinating ESA contributions to LunaNet. “Now, in the lunar context, we have the opportunity to agree on our interoperability approach from the very beginning, before the systems are actually implemented.”
“During this meeting at ESTEC, we agreed on the importance and urgency of defining a common lunar reference time, which is internationally accepted and towards which all lunar system and users may refer,” said Pietro Giordano, ESA navigation system engineer. “A joint international effort is now being launched towards achieving this.”
Each mission to the moon has operated on its own timescale from Earth. Deep space antennas have been used to keep onboard chronometers synchronized with terrestrial time at the same time to facilitate two-way communications. ESA stated that this way of working will not be sustainable in the coming lunar environment.
Time to think about time
Should a single organization be responsible for setting and maintaining lunar time? Also, should lunar time be set on an independent basis on the moon or kept synchronized with Earth? And what about time on other planets?
“Of course, the agreed time system will also have to be practical for astronauts,” said Bernhard Hufenbach, a member of the Moonlight Management Team from ESA’s Directorate of Human and Robotic Exploration. “This will be quite a challenge on a planetary surface where in the equatorial region each day is 29.5 Earth days long, including freezing fortnight-long lunar nights, with the whole of Earth just a small blue circle in the dark sky. However, having established a working time system for the moon, we can go on to do the same for other planetary destinations.”
To efficiently collaborate, the international community will have to settle on a common “selenocentric reference frame,” similar to the role played on Earth by the International Terrestrial Reference Frame, allowing the consistent measurement of precise distances between points across the planet.