The TianQin project: Current progress on science and technology

Abstract

TianQin is a planned space-based gravitational wave (GW) observatory consisting of three Earth-orbiting satellites with an orbital radius of about $10^5 \, {\rm km}$. The satellites will form an equilateral triangle constellation the plane of which is nearly perpendicular to the ecliptic plane. TianQin aims to detect GWs between $10^{-4} \, {\rm Hz}$ and $1 \, {\rm Hz}$ that can be generated by a wide variety of important astrophysical and cosmological sources, including the inspiral of Galactic ultra-compact binaries, the inspiral of stellar-mass black hole binaries, extreme mass ratio inspirals, the merger of massive black hole binaries, and possibly the energetic processes in the very early universe and exotic sources such as cosmic strings. In order to start science operations around 2035, a roadmap called the 0123 plan is being used to bring the key technologies of TianQin to maturity, supported by the construction of a series of research facilities on the ground. Two major projects of the 0123 plan are being carried out. In this process, the team has created a new-generation $17 \, {\rm cm}$ single-body hollow corner-cube retro-reflector which was launched with the QueQiao satellite on 21 May 2018; a new laser-ranging station equipped with a $1.2 \, {\rm m}$ telescope has been constructed and the station has successfully ranged to all five retro-reflectors on the Moon; and the TianQin-1 experimental satellite was launched on 20 December 2019—the first-round result shows that the satellite has exceeded all of its mission requirements.

Prospective sensitivities of atom interferometers to gravitational waves and ultralight dark matter

“…The planned future space-borne laser interferometer experiments LISA [6], TianQin [7] and Taiji [8] will be most sensitive to GWs in a lower range of frequencies ∼ 10 −3 − 10 −2 Hz, where one of the primary targets will be mergers involving the supermassive black holes (SMBHs) that infest galactic centres. Their existence begs the question how they formed, e.g., by hierarchical mergers of intermediate-mass black holes (IMBHs) beyond the pair-instability mass gap?…”

Research on Semi-Physical Simulation Testing of Inter-Satellite Laser Interference in the China Taiji Space Gravitational Wave Detection Program

“…The universe contains a vast number of environmental advantages. The most important are that it contains vacuums, is vibration-free, contains absolute zero temperatures, and is free from ground constraints; thus, space-borne laser interferometers, which can be used to observe low-frequency gravitational waves (10 −3~1 Hz), were proposed, including the LISA (Laser Interferometer Space Antenna) mission [13][14][15][16], Taiji program [17][18][19][20][21], and Tianqin program [22][23][24][25].…”

Sound velocity effects on the phase transition gravitational wave spectrum in the sound shell model

“…Future GW experiments, such as TianQin [4,5], LISA [6] and Taiji [7] etc, may be able to detect the PTGW signal from bubble collision, turbulence and sound wave mechanisms. For most cases of thermal phase transition, GW signal generated by sound wave mechanism is much more stronger [8][9][10] than GW produced by bubble collision and turbulence.…”