As you’ve probably heard, time is relative. The time you see on a clock can depend on how fast the clock is traveling or its distance from a heavy body like a planet or star (known as time dilation). A watch in orbit on the International Space Station will run faster than one on Earth as it is farther from Earth, and a watch accelerated to high speeds will run slower than a stationary one. For space exploration, clocks need to be very precise; a difference of one second can mean the difference between landing on the Moon or missing by hundreds of thousands of miles.

In 1967, Coordinated Universal Time (UTC) was adopted, incorporating measurements from around 400 extremely precise atomic clocks worldwide. Reaching a consensus among all these measurements and correcting UTC by adding ‘leap seconds,’ however, can take up to six weeks. ESA has been contributing to UTC since 2012 from its European Space Research and Technology Centre (ESTEC) in the Netherlands. However, since November 2021, it has been running on a newly defined time measured by two new atomic clocks at the European Space Operations Centre (ESOC).

“The time previously provided by ESTEC was under laboratory conditions and not used by our ground stations or missions. The main difference now is that we generate an ‘operational time,’ ready to use immediately for all missions, without interruption,” explains Werner Enderle, head of ESA’s Navigation Support Office at ESOC.

Not only does this new time determination improve the accuracy of UTC worldwide, it will also bring benefits for all ESA missions, such as Gaia, which is taking a navigation census of stars to tackle questions relating to the evolution of our galaxy. It is also a critical step towards ESA’s Lunar Pathfinder mission to take a global navigation satellite system (think GPS for satellites) to the Moon. READ MORE