A Three-Axis Attitude Measurement Method for Key Spaceborne Components Based on Dual-Path Autocollimation

Aiming to address the attitude deviations of spaceborne optical payloads caused by the coupled effects of extreme on-orbit environments, as well as the limitations of existing on-orbit measurement algorithms, including reference error propagation and the neglect of prism attitude variations, this paper proposes a three-axis attitude measurement method for key spaceborne components based on dual-path autocollimation. The proposed method constructs a two-level spatial attitude measurement chain and employs a low-thermal-expansion polyhedral prism as a unified central reference, thereby transforming the discrete measurement of multiple instruments into a transfer solution relative to a common reference. Focusing on the first-level measurement chain, a dual-path autocollimation measurement method is derived to solve the three-axis attitude angles of the remote prism. The proposed method does not rely on the actual satellite attitude reference and can directly monitor the absolute attitude deviations of spaceborne instruments, thereby laying a foundation for attitude measurement of distributed spaceborne instruments. Analysis of typical layout angles shows that a 90° orthogonal configuration enables complete decoupling of the three attitude angles, whereas a 60° acute-angle configuration is more compatible with the limited space available on a satellite and achieves partial decoupling. Moreover, when the included angle between the two autocollimators lies within 30° to 90°, the solution exhibits favorable stability, meeting the requirements of high-precision spaceborne attitude measurement.