How does a star tracker work？

First of all,the star tracker is an attitude measurement instrument that integrates optical,mechanical and electronic technologies,It is in itself a very complex system engineering.The star tracker is mainly composed of a Lens hood,an optical lens,an image sensor,an imaging circuit,an image processing circuit,a power supply and data interface,and a Machine casing.

What are the components of a star tracker?

The following is a brief introduction to the functions of each component:

Lens hood:Eliminate stray light to avoid its impact on the image quality of the star trackers;

Optical lens:The star light is mapped to the target surface of the image sensor;

Image sensor:Realize the conversion of optical signal to electrical signal;

Imaging circuit:realize the imaging drive and timing control of image sensor;

Image processing circuit:realize the image and data processing of star trackers;

Power and data interface:achieve stable power supply and data communication for star tracker.

How does a star tracker work?

The working principle of star tracker is mainly based on the detection and recognition of stars.Among them,the navigation star is the reference benchmark for star tracker to work on.After years of extensive astronomical measurements,each star has its own relatively fixed position in the celestial sphere.

At present,the angular position accuracy of navigation stars in star catalogs is sufficiently high,

The stars that meet the imaging conditions of the star trackers are selected from the star database to form the navigation star,and the navigation star list is formed.

Star tracker first use optical systems and image sensors(such as CMOS)to image the starry sky,Capture the position and brightness of the star in the observed field of view.Then,through signal processing and Star atlas recognition algorithm,the observed star position is matched with the data in the navigation star database to determine the specific identity of the observed star.Finally,the matching information is used to calculate the three-axis attitude(i.e.direction and attitude Angle)of the star trackers,so as to provide accurate spatial orientation and reference for the carrier(such as satellite,spacecraft,etc.).

In the course of work,the image lens imagines the star on the focal plane of the CMOS image sensor,the FPGA driver circuit sends timing control signals to the CMOS to ensure its normal operation.then read and preprocess the image data to extract the position and brightness information of star points.