Low-frequency gravitational wave detection via double optical clocks in space

Jianfeng Su,Qinghua Wang,Philippe Jetzer,Qiang Wang

doi:10.1088/1361-6382/aab2eb

Abstract

We propose a Doppler tracking system for gravitational wave detection via double optical clocks in space (DOCS). In this configuration two spacecrafts (each containing an optical clock) are launched to space for Doppler shift observations. Compared to the similar attempt of gravitational wave detection in the Cassini mission, the radio signal of DOCS that contains the relative frequency changes avoids completely noise effects due for instance to troposphere, ionosphere, ground-based antenna and transponder. Given the high stabilities of the two optical clocks (Allan deviation ∼ @ 1000 s), an overall estimated sensitivity of could be achieved with an observation time of 2 yr, and would allow to detect gravitational waves in the frequency range from ∼10−4 Hz to ∼10−2 Hz.

Highlights

Gravitational waves (GWs) were predicted in the theory of general relativity (GR) more than a century ago by A Einstein, and their basic properties can be described by solving Einstein field equations [1,2,3]
We propose a Doppler tracking system for gravitational wave detection via double optical clocks in space (DOCS)
We propose a novel way of GW detection in space, which can be considered complementary to laser interferometer space antenna (LISA), and which consists of double optical clocks in space (DOCS) in order to realize Doppler tracking measurement

Summary

Introduction

Gravitational waves (GWs) were predicted in the theory of general relativity (GR) more than a century ago by A Einstein, and their basic properties can be described by solving Einstein field equations [1,2,3]. Five feasible and basic methods have been adopted in order to detect GWs: (1) laser interferometer on ground [7], (2) Doppler tracking system [8], (3) laser interferometer in space [9,10,11], (4) resonant-mass gravitational waves detectors (e.g. Weber bar) [12, 13], (5) pulsar timing arrays [14]. Among the projects of the low-frequency GW detection, the Cassini GW experiment (Doppler tracking system) by NASA finished its mission in September of 2017, but no detection evidence has been reported [15]. If the GW’s frequency is close to the resonant frequency of the mass, the deformation of the mass will be detectable Such detectors have a very narrow bandwidth because they can only detect frequencies around the resonant frequency, and no GW event has been reported. More GW detection projects based on the four methods above are summarized in [6, 13, 17]

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Conclusion