The Space Optical Clocks Project: \ud Development of high-performance \ud transportable and breadboard optical clocks and advanced subsystems

摘要

The use of ultra-precise optical clocks in space \ud(“master clocks”) will allow for a range of new applications in \udthe fields of fundamental physics (tests of Einstein's theory of \udGeneral Relativity, time and frequency metrology by means of \udthe comparison of distant terrestrial clocks), geophysics \ud(mapping of the gravitational potential of Earth), and \udastronomy (providing local oscillators for radio ranging and \udinterferometry in space). Within the ELIPS-3 program of ESA, \udthe “Space Optical Clocks” (SOC) project aims to install and to \udoperate an optical lattice clock on the ISS towards the end of this \uddecade, as a natural follow-on to the ACES mission, improving \udits performance by at least one order of magnitude. The payload \udis planned to include an optical lattice clock, as well as a \udfrequency comb, a microwave link, and an optical link for \udcomparisons of the ISS clock with ground clocks located in \udseveral countries and continents. Undertaking a necessary step \udtowards optical clocks in space, the EU-FP7-SPACE-2010-1 \udproject no. 263500 (SOC2) (2011-2015) aims at two “engineering \udconfidence“, accurate transportable lattice optical clock \uddemonstrators having relative frequency instability below \ud1×10\ud-15\udat 1 s integration time and relative inaccuracy below \ud5×10\ud-17\ud. This goal performance is about 2 and 1 orders better in \udinstability and inaccuracy, respectively, than today’s best \udtransportable clocks. The devices will be based on trapped \udneutral ytterbium and strontium atoms. One device will be a \udbreadboard. The two systems will be validated in laboratory \udenvironments and their performance will be established by \udcomparison with laboratory optical clocks and primary \udfrequency standards. In order to achieve the goals, SOC2 will \uddevelop the necessary laser systems - adapted in terms of power, \udlinewidth, frequency stability, long-term reliability, and \udaccuracy. Novel solutions with reduced space, power and mass \udrequirements will be implemented. Some of the laser systems \udwill be developed towards particularly high compactness and \udrobustness levels. Also, the project will validate crucial laser \udcomponents in relevant environments. In this paper we present \udthe project and the results achieved during the first year