TianQin Research Articles

Magnetic field dynamics and noise analysis for space-based GW detector in far-earth orbits: A hybrid modeling approach

TianQin (TQ) mission, the sole proposed gravitational wave detection project in geocentric orbit at an altitude of approximately 105 km, traverses diverse geomagnetic regions. This paper employs a hybrid model to simulate the ambient magnetic field along the TQ orbit, investigating magnetically-induced acceleration noise under varying satellite-sun angles (SSA) and solar activity levels. The highest noise level, approximately 10−16ms−2Hz−1/2, occurs during transregional periods between the magnetosheath (MSH) and magnetotail (MTL). Noise within the MSH region is an order of magnitude lower than the former, with the MTL region exhibiting the lowest levels, although geomagnetic storms can equalize noise in both regions. Statistical analysis indicates that noise in the MTL region correlates with SSA and solar wind dynamic pressure, displaying a spectral characteristic of f−1.03±0.075, while the MSH region shows a Kolmogorov turbulence spectrum near the flank and f−0.5 at the subsolar region.

Multimessenger observations of double neutron stars in the Galactic disk with gravitational and radio waves

We evaluate the prospects for radio follow-up of the double neutron stars (DNSs) in the Galactic disk that could be detected through future space-borne gravitational wave (GW) detectors. We first simulate the DNS population in the Galactic disk that is accessible to space-borne GW detectors according to the merger rate from recent LIGO results. Using the inspiraling waveform for the eccentric binary, the average number of the DNSs detectable by TianQin (TQ), LISA, and $\mathrm{TQ}+\mathrm{LISA}$ are 217, 368, and 429, respectively. For the joint GW detection of $\mathrm{TQ}+\mathrm{LISA}$, the forecasted parameter estimation accuracies, based on the Fisher information matrix, for the detectable sources can reach the levels of $\mathrm{\ensuremath{\Delta}}{P}_{\mathrm{b}}/{P}_{\mathrm{b}}\ensuremath{\lesssim}{10}^{\ensuremath{-}6}$, $\mathrm{\ensuremath{\Delta}}\mathrm{\ensuremath{\Omega}}\ensuremath{\lesssim}100\text{ }\text{ }{\mathrm{deg}}^{2}$, $\mathrm{\ensuremath{\Delta}}e/e\ensuremath{\lesssim}0.3$, and $\mathrm{\ensuremath{\Delta}}{\stackrel{\ifmmode \dot{}\else \textperiodcentered \fi{}}{P}}_{\mathrm{b}}/{\stackrel{\ifmmode \dot{}\else \textperiodcentered \fi{}}{P}}_{\mathrm{b}}\ensuremath{\lesssim}0.02$. These estimation accuracies are fitted in the form of power-law function of signal-to-noise ratio. Next, we simulate the radio pulse emission from the possible pulsars in these DNSs according to pulsar beam geometry and the empirical distributions of spin period and luminosity. For the DNSs detectable by $\mathrm{TQ}+\mathrm{LISA}$, the average number of DNSs detectable by the follow-up pulsar searches using the Parkes, FAST, SKA1, and SKA are 8, 10, 43, and 87, respectively. Depending on the radio telescope, the average distances of these GW-detectable pulsar binaries vary from 1 to 7 kpc. Considering the dominant radiometer noise and phase jitter noise, the timing accuracy of these GW-detectable pulsars can be as low as 70 ns while the most probable value is about $100\text{ }\text{ }\mathrm{\ensuremath{\mu}}\mathrm{s}$.

Drag-free control design and in-orbit validation of TianQin-1 satellite

Drag-free control (DFC) is one of the key technologies for space-borne gravitational wave detectors. For the TianQin (TQ) project, non-gravitational disturbances on the spacecraft must be suppressed by DFC. TianQin-1 (TQ-1) is the first satellite for technology verification, whose main goal is to verify the disturbances reduction technologies. In this paper, the DFC requirement and preliminary analysis for the TQ project are introduced, and then the design and the experimental validation with the TQ-1 satellite is presented. In-orbit results show a successful validation of DFC and the residual acceleration of TQ-1 satellite has been suppressed to at 10 mHz versus thruster noise.

In memory of Professor Tianqin Cao (Tien-chin Tsao)

In memory of Professor Tianqin Cao (Tien-chin Tsao)