Enhancing Navigation Satellites: A Leap in Atomic Clock Technology
by Erica Marchand
Paris, France (SPX) Jan 11, 2024

A recent microscopic image, resembling an alien landscape but actually a scanning electron microscope view of a test glass surface, is at the forefront of a novel project aimed at enhancing the longevity of spaceborne atomic clocks, which are central to navigation satellites. These atomic clocks, found in the heart of systems like the European Union's Galileo satellites, are instrumental in ensuring precise navigation by providing exceptionally stable timekeeping.

This image, with features smaller than 10 micrometres - a hundredth of a millimetre - across, reveals the intricate details of plasma-etched glass used in atomic clocks. The sharp, conical patterns, a result of etching mechanisms and related plasma effects, are part of the ongoing efforts to understand and mitigate the wear and tear on these crucial components.

Atomic clocks, like the passive hydrogen maser (PHM) used in Galileo satellites, operate by inducing switches between energy states of an atom's electron shell using light, laser, or maser energy. This process results in the emission of microwaves at a stable frequency, which is the essence of the clock's timekeeping mechanism. The precision of these clocks is staggering, with the PHM design in Galileo satellites maintaining time to an estimated accuracy of one second in three million years.

However, the sustainability of these atomic clocks faces challenges. Over time, the glass-bulb plasma confiner, where hydrogen molecules are dissociated into atoms, undergoes degradation due to chemical etching and interactions between the hydrogen plasma and glass inner walls. This degradation can affect the discharge process, thereby impacting the clock's accuracy and longevity.

The European Space Agency (ESA), in collaboration with Safran (formerly Orolia), has embarked on a Technology Development Element project to address these issues. The project focuses on characterizing the effects of chemical etching and plasma interactions to enhance the reliability of atomic clocks for space applications.

The significance of this endeavor extends beyond satellite navigation. With satellite-based telecommunications moving towards higher frequencies for higher data rates, the need for accurate time synchronization becomes more critical. Consequently, the development of smaller, chip-sized atomic clocks is under consideration.

Moreover, the enhanced versions of passive hydrogen maser and backup rubidium atomic clocks, designed for Europe's new Galileo Second Generation satellites, reflect the ongoing efforts to refine and perfect this technology.

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