More accurate than ever - New clocks for future satellite navigation DLR institutes in brief

DLR at a glance

The German Aerospace Center (DLR) is the research center of the Federal Republic of Germany for aerospace.

There are no easy comparisons of how accurate the clocks on the Galileo satellites are. Is it a matter of fractions of a second – or of milliseconds? Far too imprecise. The Galileo system has atomic clocks that are accurate to the nanosecond. A billion nanoseconds last for one second. And there's more: "The iodine laser clocks developed at the Institute for Quantum Technologies will be many times more accurate than other systems," says Prof. Felix Huber from the Galileo Competence Center at the German Aerospace Center (DLR). The better the time is determined, the safer, for example, navigation on earth.

The Galileo Competence Center in Oberpfaffenhofen was founded in 2019 and the development phase is almost complete. The competence center continuously improves the technologies for the Galileo navigation system. To this end, the inventions of the DLR institutes are being advanced together with industry so that they can be used for satellites and ground systems. The Institute for Quantum Technologies contributes the iodine laser clocks to the COMPASSO project, which is managed by the Galileo Competence Center. The iodine laser watches are now jointly qualified for use in space: they have to be particularly small, robust and durable. For the COMPASSO project, the Institute for Communication and Navigation has also worked with business partners to develop a laser terminal that transmits the data, synchronizes the satellite clocks and determines distances with great precision. There is also a frequency comb and other instruments that support experiments in space. The frequency comb transmits the optical signals into the frequency range for satellite navigation. The Institute for Software Technology supplies the operating software for the computer that controls the experiments. DLR Space Operations supports and takes over the preparation and execution of the entire operation.

Minimal deviation with a big effect

The Galileo satellite navigation system already offers exceptionally high positioning accuracy and precise time information. During navigation, satellites constantly send data so that users can determine their location. It is immensely important that the propagation times between transmitter and receiver are correctly interpreted: "An inaccuracy in the time measurement of one nanosecond would correspond to an error of 30 centimeters in the distance measurement," explains Felix Huber. That doesn't seem like much - after all, the satellites orbit the earth at an altitude of about 23,000 kilometers. But: That would not be tolerable when navigating automated vehicles. "The atomic clocks in the satellites have to match so precisely that they allow real-time positioning accuracy in the range of a few centimeters," says Felix Huber.

The iodine laser clocks from the COMPASSO project are based on the principles of quantum mechanics. It describes physical processes at the atomic level - i.e. in the world of the very smallest. In addition to the DLR Institute for Quantum Technologies in Ulm and the DLR Institute for Satellite Geodesy and Inertial Sensors in Hanover, the Galileo Competence Center plays an important role in terrestrial and space-based quantum innovations. Of course, the focus is also on research and development work for future quantum computers.

Great value for users

How should future systems be designed in order to achieve the greatest benefit? Which technologies make a difference? And which ones have market potential? The Galileo Competence Center is also investigating this in the Robust Precise Timing Facility (RPTF) project. In contrast to COMPASSO, no space technologies are qualified here, but the ground systems required for Galileo operation are further developed. This is hardware and software for perfect time distribution in the Galileo system. The measuring instruments on earth can be expanded at will. They act as a kind of "team" and deliver perfect times even if some of them should fail or be replaced. "The reference time on the ground must always remain reliable for the satellites," explains Felix Huber. Side effect of the "Robust Precise Timing Facility": It is so stable that it can be used in other systems for maintenance and troubleshooting.

"The research comes from the institutes," says Felix Huber. In the case of the RPTF, it is primarily the DLR Institute for Communications and Navigation. The Galileo Competence Center ensures that new ideas are launched. It supports technology transfer so that the research results can be implemented together with industrial partners.

DLR at a glance

The German Aerospace Center (DLR) is the research center of the Federal Republic of Germany for aerospace.