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 technology, for stabilization and navigation of satellite launcher during its mission. Rather than adopting the NED reference frame and a 3-2-1 Euler angles, which are mostly used in atmospheric flights for attitude determination, in space flight (satellite carrier rockets) the LPI (Launch-Point-Inertial) reference frame is preferred 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; indeed if for other electronic components, such as FCC, mechanical isolation is not a problem, it becomes the main problem for a system that “work” with the inertial movements of the rocket. 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. Mechanical and special firmware has been developed in order to “follows” inertial movements and at the same time protect sensors while very high shock (pyrotechnic shock of 10000g) happens. Finally some experimental results on achieved accuracy are presented.