Space-Qualified Star Tracker for Small Satellites

Role and Importance of Star Trackers

A star tracker is a high-precision instrument used to determine a spacecraft’s attitude. For small satellites, star trackers are critical for attitude control. Given the stringent size, weight, and power (SWaP) constraints of small satellites, star trackers must deliver high performance within a compact design.

Key Features of Star Tracker for Small Satellites

1. Compact Size and Weight
   Designed to be as small and lightweight as possible.
2. Low Power Consumption
   Suitable for low-power missions.
3. High Accuracy
   Precision is a core requirement, directly impacting the quality of attitude control.
4. Radiation Resistance
   Capable of withstanding space radiation.
5. Operational Lifespan
   Designed for durability in space environments.
6. Interface and Compatibility
   Seamless integration with satellite systems.
7. Baffle Options
   To mitigate stray light interference.
8. Update Rate and Angular Velocity
   Supports high-frequency updates and rapid attitude changes.

Criteria for Selecting a Star Tracker

1. Mission Requirements
   Orbit type, mission duration, and accuracy needs dictate star tracker specifications.
2. Satellite Platform Constraints
   Physical limitations of small satellites must align with the star tracker’s specifications.
3. Budget
   Cost is a key factor for small satellite projects. Standardized components can reduce costs while maintaining high performance, ideal for budget-constrained missions.
4. Flight Heritage and Reliability
   Choosing models with proven flight heritage minimizes mission risks.
5. Ease of Integration
   Plug-and-play designs and shorter lead times accelerate project timelines.

Considerations for Using Star Trackers

Environmental Factors

Temperature Range: Ensure the star tracker operates within the expected temperature range.

Radiation Protection: Verify radiation tolerance matches the target orbit.

Light Interference

Sunlight, thruster plumes, or other light sources may disrupt star identification algorithms. Appropriate baffles can effectively reduce interference.

Be mindful of reflections from spacecraft surfaces or exhaust plumes during thruster sequences.

Error Sources

Star trackers may be affected by spatial frequency errors, temporal errors, and optical errors (e.g., spherical aberration or chromatic aberration).

Maintenance Needs

Star trackers typically require minimal maintenance but may need periodic calibration or star catalog updates to maintain accuracy.

Ensure the star catalog filters out unreliable stars (e.g., those with high magnitude variability).

System Compatibility

Ensure compatibility with the satellite’s attitude control system and other subsystems.

Verify power supply compatibility (e.g., ST400’s 3.6V–34.0V range) and power consumption.

Additional Considerations

Star trackers may be used for space debris detection or satellite identification, requiring algorithms to distinguish stars from other light sources.

For complex missions, multiple star trackers may need to be networked to cover different fields of view.