In fact, lunar operations will depend on interoperable GNSS time – precise, lunar access to an agreed ‘now’, allowing for multi-mission, multi-user operations on and around the Moon. ESA has recently been charged by the International Committee on Global Navigation Satellite Systems with proposing potential concepts for such an interoperable GNSS time, which could also be used for lunar missions. The recent UTC determination at ESOC is a fundamental step towards the goal.

Not only does ‘ESA time’ help improve the accuracy of UTC worldwide, but it means all the Agency’s missions, now and in the future, home and away, will benefit from an immediate, precise answer to the seemingly simple question, “what time is it?”