Asteroids for $μ$Hz gravitational-wave detection

Abstract

A major challenge for gravitational-wave (GW) detection in the µHz 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 µHz band. We show that a wide variety of environmental perturbations are small enough to enable an appropriate class of ∼ 10 km-diameter asteroids to be employed as TMs. This would allow a sensitive GW detector in the band (few) × 10 −7 Hz fgw (few) × 10 −5 Hz, reaching strain hc ∼ 10 −19 around fgw ∼ 10 µHz, 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 (EM) 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 EM pulse travel time via laser ranging. Tradespace 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.

Cold Atoms in Space: Community Workshop Summary and Proposed Road-Map

“…We note also that timing measurements using atomic clocks located on asteroids have been proposed as a way to measure gravitational waves in the µHz range[244], in the gap between LISA and pulsar timing arrays 15. We comment in passing that radio astronomy would gain greatly from extending the Event Horizon Telescope[246] concept to a space mission with a much longer baseline, which would benefit from using atomic clocks for synchronization.…”

Snowmass 2021: Quantum Sensors for HEP Science -- Interferometers, Mechanics, Traps, and Clocks

“…Future clock development will provide further orders of magnitude of improvement for these experiments. Deployment of high-precision clocks in space will also open the door to new applications, including precision tests of gravity and relativity [210], searches for a dark-matter halo bound to the Sun [211], and gravitational wave detection in wavelength ranges inaccessible on Earth [212,213].…”

Astrometric Gravitational-Wave Detection via Stellar Interferometry

“…For M wd ∼ 0.6 M , this implies that the planetary body must have an orbital semi-major axis a around the star in the range 0.1 AU a 2 AU, in order for the fundamental orbital period to lie in the measurement band; higher harmonics of the orbital frequency will also enter for eccentric orbits, but are suppressed (see discussions in, e.g., Refs. [43,56]).…”

“…These include pulsar timing arrays (PTAs) [6][7][8][15][16][17][18][19][20] that operate around nHz-µHz; the LISA constellation [21][22][23] that is aimed at 1-10 mHz; TianQin aimed at 0.01 Hz-1 Hz [24,25]; atomic-interferometry approaches such as MAGIS/MIGA/AION/AEDGE/ZAIGA [26][27][28][29][30][31][32][33][34][35][36][37] around 1 Hz; clock-based proposals [38] between mHz and Hz; DECIGO at 0.1-10 Hz [39,40]; and Cosmic Explorer [41] and the Einstein Telescope [42] above ∼ 10 Hz. Concepts have also been developed to detect gravitational waves in the µHz-mHz band using LISA-style constellations [11], using asteroids as test masses in a future space-based mission [43], studying orbital perturbations to various binary systems [44,45], and looking for low-frequency modulation of higher-frequency GWs [46]. Existing astrometric studies (e.g., Refs.…”

“…Most existing proposals in the 10 nHz-µHz band do not have sufficient sensitivity to access this level of strain (although see Refs. [11,43] for mission concepts that may be able to achieve this sensitivity).…”