Overview
sunSafePoint computes an attitude guidance error message that steers a desired body vector (e.g., a solar panel normal) toward the measured sun direction. When the sun measurement is lost or below the minimum acceptable norm, the module commands a safe spin about a fallback eigenaxis.
Configuration parameters
Desired body-frame unit vector to point toward the sun (e.g., a solar panel normal or an instrument boresight).
Minimum acceptable norm of the sun-direction vector. If the measured sun vector norm falls below this threshold, the module switches to the safe-spin mode.
Angular threshold [rad] below which the attitude error is treated as near 0° or 180°, selecting the appropriate rotation path.
Eigenaxis to use when the commanded direction is 180° from the measured sun direction (to avoid a singularity).
Desired body angular-rate vector [rad/s] commanded when no valid sun measurement is available (safe-spin mode).
Constant spin rate [rad/s] about the sun heading vector to maintain power generation while sun pointing.
Input messages
Navigation attitude message containing the measured sun-direction vector in the body frame.
IMU navigation attitude message providing the current spacecraft angular velocity.
Output messages
Attitude guidance output message containing
sigma_BR (MRP error), omega_BR_B (rate error), omega_RN_B (reference rate), and domega_RN_B (reference angular acceleration).