The Astrometric Performance of the China Space Station Telescope (CSST) Sky Survey in Extending the Gaia Celestial Reference Frame

Abstract

The multi-color imaging sky survey conducted by the China Space Station Telescope (CSST) holds significant promise for advancing the development of the celestial reference frame. In this study, we focus on assessing the astrometric performance of the CSST celestial reference frame (CSST-CRF) in extending the Gaia Celestial Reference Frame 3 (Gaia-CRF3). First, the orientation precision of the CSST reference frame is evaluated using a simulated set of extragalactic sources with CSST g magnitudes ranging from 18 to 25 mag. The estimated orientation uncertainty caused by random error insignificantly affects the alignment between Gaia-CRF3 and the CSST-CRF. Then, the systematic effect of incomplete CSST sky coverage on the alignment between CSST-CRF and Gaia-CRF3 is discussed by analyzing the differences between the subset of Gaia-CRF3 in the CSST observation region (Gaia-CRF3′) and Gaia-CRF3 as a whole. Using the third International Celestial Reference Frame (ICRF3) S/X band as an intermediate reference frame, the orientation offset between Gaia-CRF3′ and Gaia-CRF3 is estimated to be 20 μas. This offset is marginally larger than the orientation offset between Gaia-CRF3 and the ICRF3, approximately 15 μas. The residual spin and glide rate of Gaia-CRF3′ are derived from the proper motions, consistent with that of Gaia-CRF3 within the formal error. Finally, we explore the role of CSST in establishing a multi-band celestial reference frame by comparing its limiting magnitude and observation accuracy with existing catalogs in the infrared and ultraviolet bands. Thanks to its broad wavelength coverage and high-precision measurements, CSST is well-positioned to make significant contributions to the development of a multi-band celestial reference frame.