Development of a strontium optical lattice clock for the SOC mission on the ISS

TL;DR

This paper reports the development of a compact, high-precision strontium optical lattice clock designed for space deployment on the ISS, aiming to enable advanced tests of physics and geodesy.

Contribution

It introduces a fully operational strontium optical lattice clock with space-compatible design features and demonstrates its performance metrics.

Findings

Clock transition observed with 9 Hz linewidth

Instability below 1×10⁻¹⁵ τ⁻¹/² achieved

Fractional inaccuracy of 5×10⁻¹⁷ demonstrated

Abstract

The ESA mission "Space Optical Clock" project aims at operating an optical lattice clock on the ISS in approximately 2023. The scientific goals of the mission are to perform tests of fundamental physics, to enable space-assisted relativistic geodesy and to intercompare optical clocks on the ground using microwave and optical links. The performance goal of the space clock is less than $1 \times 10^{-17}$ uncertainty and $1 \times 10^{-15} {\tau}^{-1/2}$ instability. Within an EU-FP7-funded project, a strontium optical lattice clock demonstrator has been developed. Goal performances are instability below $1 \times 10^{-15} {\tau}^{-1/2}$ and fractional inaccuracy $5 \times 10^{-17}$. For the design of the clock, techniques and approaches suitable for later space application are used, such as modular design, diode lasers, low power consumption subunits, and compact dimensions. The Sr clock apparatus is fully operational, and the clock transition in $^{88}$Sr was observed with linewidth as small as 9 Hz.