FOG based INS for satellite launcher application

Spatial missions begin with orbit immission of a satellite in parking orbit by means of a satellite launcher. Civitanavi Systems developed an Inertial Navigation Systems (INS), based on proprietary FOG (Fiber Optic Gyro) technology, for stabilization and navigation of a satellite launcher during its mission. Rather than adopting the NED (North East Down) reference frame and a 3-2-1 Euler angles, which are mostly used in atmospheric flights for attitude determination, the LPI (Launch-Point-Inertial) reference frame is preferred in space flights (satellite carrier rockets) with 2-3-1 Euler angles orientation representation; hence different inertial navigation equations are derived for this special application. Main characteristics required for a satellite launcher INS are its capability to withstand harsh operating environment in terms of mechanical vibrations and shocks. Lateral booster detachment by means of propellant (explosive charges) induces a 10000g pyroshock on the INS unit exciting frequencies up to 5000 Hz. Special requirements are derived in terms of mechanical design and FOG control law enhancement in order to stabilize closed-loop FOG during high angular acceleration phase (shock) and to reject spurious dynamic measurements. Finally some experimental results on achieved accuracy are presented.