Data Transmission Analysis and Communication Scheme Design for TianQin Mission

Compared with ground-based gravitational wave detection, space-based gravitational wave detection has become a research hotspot because of its abundant wave sources. However, how to reliably transmit the detection data, obtained by the space gravitational wave detector, back to the ground station from a distance of 105 kilometers is a huge challenge. In this paper, the visibility analysis and link budget are carried out for the data transmission of gravitational wave detection in geocentric orbit space, and a high real-time data transmission scheme is provided to support the mHz band gravitational wave detection. In more detail, we firstly establish a theoretical model for visibility analysis and link budget based on spacecraft dynamics model and communication link model. Secondly, through visibility simulation and calculation, we obtained the average communication time per day, and found that the Zhuhai station has a more uniform distribution of communication time compared with other ground stations. Subsequently, the link budget model indicates that link performance is largely determined by various gains and attenuations during the link process, which are related to the link working frequency band and resource allocation. Comparing the differences on gain and attenuation between X-band and Ka-band, we design an X-band communication scheme with the transmission rate of 1Mbps and bit error rate of 10−5. The calculation results also show that the communication scheme has a C/N₀ margin of 4.10 dB, which meets the data transmission requirements of TianQin. Finally, the research shows that compared with the heliocentric orbit of LISA, the geocentric orbit of TianQin has obvious advantages in transmission delay, communication time and real-time performance of data transmission, avoiding the antenna pointing issues and is more conducive to the multi-messenger detection of large astronomical events.