What is the function of star tracker

Star tracker serve as spacecraft “eyes.” They use fixed star patterns as references. Thus, they determine the spacecraft’s attitude in 3D space.

Star trackers are optical devices. They feature high-resolution cameras or photoelectric sensors. These capture starfield images. Then, complex algorithms match observed stars with built-in star catalogs. Consequently, they compute precise spacecraft attitude.

Star Tracker Workflow

1. Imaging: The lens targets a starfield region. CMOS or CCD sensors capture bright star points.
2. Star Extraction: The system identifies star points. It measures angular distances and relative positions.
3. Pattern Matching: It compares extracted patterns with preloaded star catalogs (holding thousands to tens of thousands of known star positions).
4. Attitude Calculation: Using triangulation and matrix operations, it outputs real-time quaternions or Euler angles relative to inertial space.

Key Functions in Spacecraft

1. Attitude Stability and Precise Pointing

– GEO communication satellites: Star trackers keep antennas aligned with ground stations. Thus, signals remain uninterrupted.

2. Autonomous Deep-Space Navigation

– In deep space, signals delay for hours. Star trackers enable rapid initial attitude acquisition after launch or maneuvers. They need no ground support.

3. Error Correction and System Redundancy

– Combined with gyroscopes and sun sensors, they periodically correct gyro drift errors.

4. Support for Advanced Missions

– Laser Communication: On ESA’s Alphasat, star trackers boost beam pointing to micro-arcsecond accuracy.

Star Tracker Advantages

– Ultra-High Precision: Sub-arcsecond level; preferred for deep space.

– All-Weather Availability: Stars never “disappear” if bright sources are avoided.

– Low Power, Long Life: No moving parts; typical lifespan exceeds 15 years.

– Radiation-Hardened Design: Uses hardened electronics; suits high-radiation zones like Jupiter orbit.