## 1 Introduction  
In recent years, the demand for optical space exploration has led to the development of space optical telescopes in the direction of multi-functionality with tens of meters or even longer focal lengths, five meters or even larger apertures, splicing, and in-orbit assembly to meet their requirements for high resolution and diversification of measurement objects [1, 2, 3]. At present, off-axis space telescopes usually adopt a composite truss support structure, which has poor stability compared with traditional material structure. Therefore, in the integration process of the space telescope, corresponding stability measurement experiments are required for mechanical structure deformation under different loads [4, 5]. In terms of datum transfer, a wide range of spatial coordinate measuring instruments were used in the 6.5 m diameter JWST project. Coordinate alignment of the IntegratedScience Instrument Module (ISIM) was done using the Unified Spatial Metrology Network (USMN) technique, with an accuracy of 0.26 mm for rigid body change position measurements and 0.002\({}^{\circ}\) for angular accuracy after relational fitting. In addition, the theodolite and laser tracker system was used as the main position and orientation measurement device in the vacuum cryogenic test and gravity release test experiments [6; 7; 8; 9; 10; 11; 12; 13]. [PERSON] et al. proposed a laser tracker sensor data fusion alignment algorithm for large-scale precision metrology to trim various error sources into the measurement data to improve measurement accuracy [14]. [PERSON] proposed the Mahalanobis distance-based surveying adjustment method to improve measurement equipment-transited accuracy and applied it to ground-based large millimeter telescope 3 m \(\times\) 5 m magnitude panel assembly in inspection [15]. [PERSON] et al. combined photogrammetry and laser tracker to measure common points based on an image calibration method to control the laser tracker transfer error to 0.02 mm at 6-m range [16]. [PERSON] et al. combined the radial basis function and best least-squares neural network method to reduce the average error of coordinate transformation between the laser tracker and coordinate measuring machine (CMM) to 0.054 mm within 1 m\({}^{3}\)[17]. [PERSON] et al. proposed a warp collimation virtual prism method to solve the spacecraft mounting angle [18]. The current state of research and experimental applications indicate that: (1) The increased sensitivity to misalignment during the integration of space telescopes requires test accuracy on the order of arcseconds. (2) Due to the anisotropy and complex deformation patterns of the special process composites widely used in the lightweight design of space telescopes truss structure, it is difficult for the existing data fusion measurement methods to balance sampling density and measurement accuracy. (3) As a result, relatively high measurement accuracy and high sampling density at larger scales are required, while the measurement uncertainty introduced by the underlying measurement means is not significantly reduced. In view of the above problems, combined with the needs of space telescope truss structure stability test experiments, the paper proposes to establish the relationship between the cubic prism coordinate system and the geometric coordinate system of the mounting components by the laser tracker. This method improves the accuracy from 10\({}^{\prime\prime}\) to 2\({}^{\prime\prime}\) compared to the conventional method of fitting the plane normal vector and enables fast and high-precision measurement of the cubic prism mounting angle. Based on the design model of the truss structure, the transfer process of the coordinate system reference of the truss structure is analyzed and simulated based on the Monte Carlo mathematical model, which is verified by the stability test experiment of the truss structure.