Over the years, we have supported many international space missions, large and small, with our frequency control and timing products. But to be part of the most precise timepiece ever sent to orbit, to test Einstein’s gravitational time dilation effect, is a rare honour and achievement.
On 25 April 2025, the European Space Agency’s Atomic Clock Ensemble in Space (ACES) facility was installed on the International Space Station, containing 2 new ultra-precise atomic clocks: PHARAO (Projet d’Horloge Atomique à Refroidissement d’Atomes en Orbite), managed by CNES, and SHM (Space Hydrogen Maser).
ACES integrates PHARAO’s remarkable long-term accuracy with SHM’s outstanding short-term stability, resulting in an ultra-stable, ultra-precise time signal. Together, they reach a level of accuracy so high, that ACES would drift by only a single second over a span of 300 million years. That is 10 times more precise than the atomic clocks used in today’s global positioning satellites. This breakthrough could lead to better global navigation, improve scientific experiments, and even challenge Einstein’s theory of relativity in space.
For this project Rakon developed an Ultra Stable Oscillator, featuring an extraordinary Allan Deviation (ADEV) of (1s) =7E-14, which serves as the short-term reference for both PHARAO and SHM. This space USO also boasts exceptional phase noise with a noise floor of -156 dBc/Hz @ 5 MHz and a G-sensitivity of a mere 2E-10/G.
Variations of this High Reliability Space USO have been used in the DORIS, PLEIADE, CRYOSAT2, SENTINELLE3, SWOT, JASON2, SPOT5, and HELIOS2 missions.
The current iteration of this product is the RK410 model. With a Total Ionizing Dose (TID) of 100 krad and guaranteed ageing of max. ±100 ppb over 15 years, this mini USO is designed to operate in harsh environments to deliver an exceptionally stable frequency source for long-term missions.
For customers looking for a similarly stable solution for Low Earth Orbit GNSS and PNT applications, Rakon offers the RK409AVNS, a compact Ultra-Stable Oscillator (USO) with an extraordinary Allan Variance (AV) of 2.5E-13 at tau 1 s, and a frequency stability of only ±0.2 ppb (over operating temperature -10 to 60 °C under vacuum). This product is part of Rakon’s portfolio of Newspace subsystems and oscillators, focused on optimal lead times and cost.
For more information, please visit rakon.com/space or contact us directly
Images courtesy of the European Space Agency.