Western Australia is becoming the premier southern hemisphere hub for high-precision ground-space timing missions. The University of Western Australia (UWA) is currently building a state-of-the-art optical atomic clock, and has been selected as the only southern hemisphere microwave-frequency ground station for the Atomic Clock Ensemble in Space (ACES) mission. We propose to construct a 60 km section of optical fibre to complete a link between UWA and the Yarragadee Satellite Laser Ranging facility and thereby enabling an optical link for the ACES and Space-Time Explorer and QUantum Equivalence Principle Space Test (STE-QUEST) missions.
Western Australia is becoming the premier southern hemisphere hub for high-precision ground-space timing missions. The University of Western Australia (UWA) is currently building a state-of-the-art optical atomic clock, and has been selected as the only southern hemisphere microwave-frequency ground station for the Atomic Clock Ensemble in Space (ACES) mission. We propose to construct a 60 km section of optical fibre to complete a link between UWA and the Yarragadee Satellite Laser Ranging facility and thereby enabling an optical link for the ACES and Space-Time Explorer and QUantum Equivalence Principle Space Test (STE-QUEST) missions.
We present an actuation technique for suppressing uncorrelated noise between two optical frequencies to obtain ultra-stable microwave frequency dissemination over optical fibre. This technique will enable dual optical and microwave frequency transfer between the University of Western Australia and Yarragadee Satellite Laser Ranging station, which has application for the Atomic Clock Ensemble in Space (ACES) mission and other precision navigation and timing technologies. We build on the technique presented in [1], which demonstrates microwave transfer stability of 10−14 at 1s integration time by stabilising the group delay of an two correlated optical signals. A second actuator has been developed to suppress the remaining uncorrelated phase fluctuations between two optical frequencies by implementing optical-wavelength-scale action to vary the microwave phase. The actuator has been designed with the aid of a simulation that predicts actuation bandwidth and loss for a range of actuator parameters.
The use of ultra-precise optical clocks in space (“master clocks”) will allow for a range of new applications in the fields of fundamental physics (tests of Einstein's theory of General Relativity, time and frequency metrology by means of the comparison of distant terrestrial clocks), geophysics (mapping of the gravitational potential of Earth), and astronomy (providing local oscillators for radio ranging and interferometry in space). Within the ELIPS-3 program of ESA, the “Space Optical Clocks” (SOC) project aims to install and to operate an optical lattice clock on the ISS towards the end of this decade, as a natural follow-on to the ACES mission, improving its performance by at least one order of magnitude. The payload is planned to include an optical lattice clock, as well as a frequency comb, a microwave link, and an optical link for comparisons of the ISS clock with ground clocks located in several countries and continents. Undertaking a necessary step towards optical clocks in space, the EU-FP7-SPACE-2010-1 project no. 263500 (SOC2) (2011–2015) aims at two “engineering confidence“, accurate transportable lattice optical clock demonstrators having relative frequency instability below 1×10−15at 1 s integration time and relative inaccuracy below 5×10−17. This goal performance is about 2 and 1 orders better in instability and inaccuracy, respectively, than today's best transportable clocks. The devices will be based on trapped neutral ytterbium and strontium atoms. One device will be a breadboard. The two systems will be validated in laboratory environments and their performance will be established by comparison with laboratory optical clocks and primary frequency standards. In order to achieve the goals, SOC2 will develop the necessary laser systems - adapted in terms of power, linewidth, frequency stability, long-term reliability, and accuracy. Novel solutions with reduced space, power and mass requirements will be implemented. Some of the laser systems will be developed towards particularly high compactness and robustness levels. Also, the project will validate crucial laser components in relevant environments. In this paper we present the project and the results achieved during the first year.
A global network of optical atomic clocks will enable unprecedented measurement precision in fields including tests of fundamental physics, dark matter searches, geodesy, and navigation. Free-space laser links through the turbulent atmosphere are needed to fully exploit this global network, by enabling comparisons to airborne and spaceborne clocks. We demonstrate frequency transfer over a 2.4 km atmospheric link with turbulence comparable to that of a ground-to-space link, achieving a fractional frequency stability of 6.1×10^{-21} in 300 s of integration time. We also show that clock comparison between ground and low Earth orbit will be limited by the stability of the clocks themselves after only a few seconds of integration. This significantly advances the technologies needed to realize a global timescale network of optical atomic clocks.
Ultra-precise optical clocks in space will allow new studies in fundamental physics and astronomy. Within an European Space Agency (ESA) program, the “Space Optical Clocks” (SOC) project aims to install and to operate an optical lattice clock on the International Space Station (ISS) towards the end of this decade. It would be a natural follow-on to the ACES mission, improving its performance by at least one order of magnitude. The payload is planned to include an optical lattice clock, as well as a frequency comb, a microwave link, and an optical link for comparisons of the ISS clock with ground clocks located in several countries and continents. Within the EU-FP7-SPACE-2010-1 project No. 263500, during the years 2011–2015 a compact, a modular and robust strontium lattice optical clock demonstrator has been developed. The goal performance is a fractional frequency instability below 1 × 10 − 15 τ − 1 / 2 and a fractional inaccuracy below 5 × 10 − 17 . Here we describe the current status of the apparatus' development, including the laser subsystems. The robust preparation of cold 88 Sr atoms in a second-stage magneto-optical trap (MOT) is achieved.
Space-borne quantum technologies, particularly those based on atom interferometry, are heralding a new era of strategic and robust space exploration. The unique conditions of space, characterized by low noise and low gravity environments, open up diverse possibilities for applications ranging from precise time and frequency transfer to Earth Observation and the search of new Physics. In this paper, we summarise the M-class mission proposal in response to the 2022 call in ESA's science program: Space-Time Explorer and Quantum Equivalence Principle Space Test (STE-QUEST). It consists in a satellite mission featuring a dual-species atom interferometer operating over extended durations. This mission aims to tackle three of the most fundamental questions in Physics: (i) testing the universality of free fall with an accuracy better than one part in 10−17, (ii) exploring various forms of Ultra-Light Dark Matter, and (iii) scrutinizing the foundations of Quantum Mechanics.
The theory of general relativity describes macroscopic phenomena driven by the influence of gravity while quantum mechanics brilliantly accounts for microscopic effects. Despite their tremendous individual success, a complete unification of fundamental interactions is missing and remains one of the most challenging and important quests in modern theoretical physics. The spacetime explorer and quantum equivalence principle space test satellite mission, proposed as a medium-size mission within the Cosmic Vision program of the European Space Agency (ESA), aims for testing general relativity with high precision in two experiments by performing a measurement of the gravitational redshift of the Sun and the Moon by comparing terrestrial clocks, and by performing a test of the universality of free fall of matter waves in the gravitational field of Earth comparing the trajectory of two Bose-Einstein condensates of 85Rb and 87Rb. The two ultracold atom clouds are monitored very precisely thanks to techniques of atom interferometry. This allows to reach down to an uncertainty in the Eötvös parameter of at least 2 × 10-15. In this paper, we report about the results of the phase A mission study of the atom interferometer instrument covering the description of the main payload elements, the atomic source concept, and the systematic error sources.