Star sensor testing and calibration

As the most accurate attitude measurement system on satellites, star sensor calibration and testing play an important role in improving accuracy. When the star sensor completes the installation of the focal plane, etc., the parameters of the optical system and the internal structural parameters of the star sensor have been determined, but there are certain errors with the theoretical design values.

How to use simple methods to test and calibrate the internal structural parameters and optical system parameters of the star sensor determines the accuracy level of the star sensor to a large extent. The following introduces a calibration method for the optical parameters and structural parameters of a star sensor based on optical autocollimation.

First, the principal point parameters of the star sensor are determined through the principle of high-precision theodolite and optical autocollimation; then, partial decoupling of internal parameters is achieved through the symmetry of the optical system; and finally, through the item-by-item testing of all optical parameters within the system, Realize the calibration and testing of internal parameters.

The installation and adjustment process of the star sensor basically achieves stable imaging of the star sensor and ensures the signal-to-noise ratio and star point extraction capability, which is an important prerequisite for accurate measurement.

However, the expected accuracy index of the star sensor cannot be achieved by relying only on assembly and adjustment. No matter how precise the installation and adjustment is, there will always be errors such as focal length, principal point offset, image plane tilt, distortion, etc. Calibration methods must be used to optimally estimate the key parameters that affect the accuracy of the star sensor and establish a corresponding compensation model, improve the accuracy of the star sensor to the expected index level.

In order to better calibrate the parameters of the star sensor, first, the contribution of each parameter to the accuracy of the star sensor must be quantitatively analyzed, and the quantitative constraints of each parameter of the star sensor under the specified accuracy must be given.

Secondly, decoupling and other methods are used to peel off the relevant parameters of the star sensor, calibrate each parameter, and give the calibration results and confidence intervals.

Finally, the accuracy of each parameter is synthesized according to the imaging model to form the final accuracy index.