A good helper for satellites—star sensors

The star sensor is a high-precision space attitude measurement device that uses stars as the reference system and the starry sky as the working object. By detecting stars at different positions on the celestial sphere and performing calculations, it provides accurate spatial orientations for aerospace vehicles such as satellites and spacecrafts. And benchmark, and like the inertial gyroscope, it has autonomous navigation capabilities and has important application value.

The working principle of the star sensor is: the image sensor captures starry sky images within the current field of view. The image is processed by signals to extract the position (and brightness) information of the stars in the observation field, and the star map recognition algorithm is used in the navigation star library. The corresponding matches of the observed stars are found, and these matching star pairs are used to calculate the three-axis attitude of the star sensor.

The overall structure of the star sensor includes: optical system, CMOS image circuit, FPGA processing circuit, DSP data processing circuit, mechanical structure and other parts. In the image lens, the image is formed on the focal plane of the CMOS image sensor. The driver circuit in the FPGA sends timing control signals to the CMOS. After the CMOS works normally, it reads the image data and preprocesses the read image data, including data bit conversion and real-time star point subdivision positioning. The obtained star position and brightness information is transmitted to the digital signal processor (DSP) for star map recognition and star target tracking, and finally the attitude information is output.

Star sensors usually include full-celestial sphere recognition working mode and star tracking working mode. In the all-celestial working mode, the star sensor captures a star map within the field of view through an optical lens. After the star center of mass positioning, star map recognition, and attitude calculation steps, the attitude information is directly output. In the star tracking mode, the star sensor uses a priori attitude information to enter the star tracking algorithm module, and finally calculates the current attitude information through local star point centroid positioning and identification.

So far, researchers have developed many different types of star sensor products and successfully applied them. During the research process, the researchers found that by adopting a multi-field star sensor design method, the field of view can be reduced without changing the detection magnitude, ensuring the attitude measurement accuracy of the star sensor.

Nowadays, autonomous astronomical navigation has become an important field in spacecraft technology and is also the main trend of future development. As a high-precision attitude measurement instrument, star sensors must have good development and application prospects.