Attitude information is an essential reference for the in-orbit operation of artificial satellites, and is also an important technical index to characterize the level and performance of artificial satellites. The star tracker is the sensor with the highest attitude measurement accuracy on the spacecraft and plays an irreplaceable role in high-precision mapping, remote sensing, and formation flights.
What is a star tracker?
The star tracker is a device that determines the attitude of a spacecraft by measuring the direction of the navigation star in the spacecraft coordinate system. It can provide arc-second or even sub-arc-second pointing accuracy and can realize the three-axis absolute attitude measurement of the spacecraft, while the earth sensor, magnetometer, sun sensor, etc. can only provide the measurement of one or two reference directions. Information; the navigation stars referenced by the star tracker coordinates are relatively evenly distributed throughout the celestial sphere, so a star tracker with suitable sensitivity and field of view can detect the navigation stars in almost any direction, and then provide a three-axis attitude information, which is unmatched by other attitude sensors.
What is an artificial satellite?
Artificial satellites are unmanned spacecraft that orbit the Earth in space. Artificial satellites basically move around the Earth according to the laws of celestial mechanics, however, their actual motion is very complicated due to the influence of the non-spherical Earth’s gravitational field, atmospheric drag, solar gravitation, lunar gravitation, and light pressure on different orbits. Artificial satellites are the spacecraft with the largest number of launches, the widest range of uses, and the fastest development.
Star trackers play an important role in astronomy, space science, and navigation systems. In astronomy, it helps scientists observe and study the motion, behavior, and properties of celestial bodies, thereby advancing our understanding of the universe. In space science, it is used to monitor and control the orbit, attitude, and navigation of artificial satellites, and then to ensure accurate operation and mission completion of satellites. The navigation system provides accurate navigation data by using the position and motion information of celestial bodies and helps ships, aircraft, vehicles, etc. to locate and navigate.
Application of Star Tracker on Artificial Satellite
1. Celestial Observation:
Star trackers provide accurate trajectory information about celestial objects by using optical, infrared, radar, and other sensors and telescopes and other devices, observe the position, brightness, speed, and other related parameters of the celestial bodies, and precisely measuring the position and motion of celestial objects.
2. Data processing:
Star trackers collected the astronomical observation data, and processed and analyzed it to extract useful information. Data processing involves technologies such as image processing, data filtering, model fitting, and numerical calculation. Star trackers can determine the precise position, velocity, direction, and orbital parameters of celestial bodies via the processing of observational data.
3. Positioning and Navigation:
To provide accurate positioning and navigation data, star trackers use the position information of observed celestial bodies. By tracking celestial bodies, calculate the satellite’s current position and velocity, and predict changes in future positions. These positioning and navigation data are critical to the accurate control and mission execution of satellites.
4. Attitude control and stabilization:
By monitoring the attitude of the satellite and related control signals, and analyzing the position and motion of celestial bodies, star trackers help satellites maintain the desired attitude, and realize stable operation and precise positioning.
5. Communication and data transmission:
Star trackers also be used for communication and data transmission on satellites. It can help satellites ensure accurate transmission and reception of signals, and improve communication quality and reliability by tracking the location of ground receiving stations or other communication satellites.
6. Energy management and solar energy utilization:
For energy management and solar energy utilization of satellites, star trackers can help satellites adjust the orientation of solar panels to maximize solar energy absorption and to provide the power supply by tracking the position and trajectory of the sun.
How does Star Tracker Work?
- Observe celestial bodies
- Data collection
- Data processing
- Orbit calculation and prediction
- Navigation and Control
Structure of a star tracker
The star tracker is mainly composed of a baffle, an optical lens, an image sensor, an imaging circuit, an image processing circuit, a power supply, a data connector, and a casing.
- Baffle: Eliminate stray light and prevent it from affecting the imaging quality of the star tracker;
- Optical lens: to map starlight onto the target surface of the image sensor;
- Image sensor: realize the conversion of the optical signal to an electrical signal;
- Imaging circuit: realize the imaging drive and timing control of the image sensor;
- Image processing circuit: realize the processing of images and data;
- Power supply and data connector: realize the stable power supply and data communication of the star tracker.
The star tracker is mainly divided into two parts: the imaging system and the image processing system from the working principle. It first uses an optical lens and an image sensor to image stars, obtains the position and brightness information of the star point on the target surface of the image sensor through star point extraction and centroid positioning, and then obtains the star corresponding to the star point in the star catalog through star map recognition. Finally, according to the recognition results, the three-axis attitude of the star tracker is obtained through attitude calculation, and the attitude data is provided for the vehicle control system to realize the navigation of the vehicle.
With the exploration of space and interstellar voyages, star trackers will play an important role in deep space exploration missions. To detect and track planets, stars, and other cosmic bodies, they can help measure and study the nature and evolution of the universe, and provide navigation and positioning support for future interstellar voyages.
TY-SPACE is an enterprise focusing on the research and development of star trackers. TY-SPACE has independently developed and produced PST and NST series of star trackers, which have played an important role in the practice of major national space missions such as the Lunar exploration project and Gaofen projects. For a variety of applications, TY-SPACE provides professional, advanced, and economical products.