Star tracker attitude determination is the process where a spacecraft uses an optical imaging device—a star tracker—to capture star images, match them with an on-board star catalog, and calculate its real-time three-axis attitude (pitch, yaw, and roll angles) relative to inertial space.
The optical system, including baffle, lens, and focal plane detector, captures star images in the current field of view and suppresses strong light interference from the Sun, Earth, and Moon.
Image processing algorithms precisely calculate the sub-pixel centroid position of each star and suppress noise, hot pixels, and radiation spots.
The algorithm quickly matches observed inter-star angles and brightness patterns with the on-board star catalog. It completes star identification in seconds, even without prior attitude information.
Using at least 3–4 identified stars, the algorithm computes the current attitude quaternion or direction cosine matrix.
A Kalman filter (EKF/UKF) fuses the star tracker’s high-accuracy, low-frequency output with the gyroscope’s high-frequency output. This produces higher update rate, smoother attitude and angular velocity estimates, and enables fault detection and isolation.
Advantages of Star Trackers in Attitude Determination
Extremely high accuracy: Star trackers outperform traditional sensors by 1–2 orders of magnitude. They meet demands for imaging remote sensing, laser communication, and deep-space precision guidance.
All-day, all-sky autonomous operation: They work without geomagnetic or GPS limitations. Thus, they suit both deep space and near-Earth orbits.
No drift: Unlike gyroscopes, star trackers have no integration drift. Therefore, they serve as long-term attitude references to calibrate other sensors.
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TY-Space Technology (Beijing) Ltd. is professional focusing on advanced attitude optical sensors, especially Star Trackers for space industry.
