Navigation vents
PLATFORM Small End Forward Mode Position
Used to align the platform with the horizon sensors when the spacecraft is flying small end forward. Horizon sensor pitch and roll outputs are compared with synchro outputs and the difference used to torque gimbals. When synchro and horizon sensor outputs are balanced the gimbals are aligned to earth local vertical. A gyro compass loop aligns the yaw gimbal with the orbit plane.
NOTE: If horizon sensors lose track during SEF alignment mode, the platform is automatically switched to ORB RATE mode.