Asteroids for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>μ</mml:mi><mml:mi>Hz</mml:mi></mml:mrow></mml:math> gravitational-wave detection

Abstract

A major challenge for gravitational-wave (GW) detection in the $\ensuremath{\mu}\mathrm{Hz}$ band is engineering a test mass (TM) with sufficiently low acceleration noise. We propose a GW detection concept using asteroids located in the inner Solar System as TMs. Our main purpose is to evaluate the acceleration noise of asteroids in the $\ensuremath{\mu}\mathrm{Hz}$ band. We show that a wide variety of environmental perturbations are small enough to enable an appropriate class of $\ensuremath{\sim}10\text{ }\text{ }\mathrm{km}$-diameter asteroids to be employed as TMs. This would allow a sensitive GW detector in the band $(\mathrm{few})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}\text{ }\text{ }\mathrm{Hz}\ensuremath{\lesssim}{f}_{\mathrm{GW}}\ensuremath{\lesssim}(\mathrm{few})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\text{ }\text{ }\mathrm{Hz}$, reaching strain ${h}_{c}\ensuremath{\sim}{10}^{\ensuremath{-}19}$ around ${f}_{\mathrm{GW}}\ensuremath{\sim}10\text{ }\text{ }\ensuremath{\mu}\mathrm{Hz}$, sufficient to detect a wide variety of sources. To exploit these asteroid TMs, human-engineered base stations could be deployed on multiple asteroids, each equipped with an electromagnetic transmitter/receiver to permit measurement of variations in the distance between them. We discuss a potential conceptual design with two base stations, each with a space-qualified optical atomic clock measuring the round-trip electromagnetic pulse travel time via laser ranging. Trade space exists to optimize multiple aspects of this mission: for example, using a radio-ranging or interferometric link system instead of laser ranging. This motivates future dedicated technical design study. This mission concept holds exceptional promise for accessing this GW frequency band.

Topics & Concepts