A star tracker is a device used in astronomy and space exploration to precisely determine the orientation and position of a spacecraft or satellite in space. It works by capturing images of stars and using their positions to calculate the spacecraft's attitude (orientation) with respect to the celestial sphere.
How Star Trackers Work？
1.Image Acquisition:
The star tracker's camera captures images of the night sky, including stars and other celestial objects. The camera's exposure time is usually set to capture stars of different magnitudes.
2.Star Identification:
The captured images are processed to identify the stars within them. This involves comparing the observed star patterns with a catalog of known stars to determine which stars are present in the image.
3.Attitude Determination:
Once the stars in the image are identified, the star tracker compares their positions with the expected positions based on the catalog data. By analyzing the differences between observed and expected positions, the star tracker determines the spacecraft's attitude and its angular displacement in relation to the stars.
4.Attitude Control:
The determined attitude information is used to adjust the orientation of the spacecraft using onboard control systems like reaction wheels, thrusters, or gyroscopes. This helps maintain or change the spacecraft's desired orientation in space.
Star trackers offer high precision and accuracy in determining spacecraft attitude, as star positions are relatively fixed in the celestial sphere. They are commonly used in various space missions, including Earth observation, satellite communications, and deep space exploration. By continuously tracking stars, the star tracker enables the spacecraft to navigate, point instruments accurately, and conduct scientific observations.