What is the role of a star tracker in integrated navigation?

• A. Calibrates the inertial measurement unit biases.
• B. Provides absolute attitude reference by observing stars.
• C. Measures vehicle speed.
• D. Estimates position from celestial navigation.

Answer: (B)

A star tracker provides an absolute attitude reference by observing stars. It images the star field, identifies which stars are seen, and matches that pattern to a known catalog to determine the vehicle’s orientation in the inertial frame. In integrated navigation, this precise attitude reference is fused with inertial measurements to correct gyroscope drift and biases, keeping the attitude estimate accurate over time. It doesn’t calibrate IMU biases directly, nor does it measure speed, nor determine position through celestial navigation. By supplying a stable, absolute orientation, the star tracker strengthens the overall navigation solution.