The New GNS Tracking Method in Launch Vehicle Spin Motion and Flight Assessment of the Radio Navigation and Inertial Navigation Sensor (RINA)
Aya Haruki, Koji Sunami, Satoshi Yamazaki, Michio Kawakami, Space Technology Directorate?/ Security and Information Systems Department, Japan Aerospace Exploration Agency, Japan
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Highly accurate navigation is crucial to the flight safety for launch vehicles. JAXA has been developing an integrated navigation system of GNSS/INS measurements, the Radio and Inertial Navigation sensor (RINA). It is designed to provide highly accurate and robust navigation through all mission phases from lift-off to ascent to reentry. We have achieved the highly accurate navigation system with low cost by adopting Micro-Electro-Mechanical System (MEMS) to correct errors of GNSS measurement. Using the 29th flight of the H-IIA, Japan’s mainstay liquid-propellant launch vehicle, we verified that RINA’s measurement accuracy satisfied the requirements of the flight safety.
In Dec. 2016, we conducted the demonstration of RINA on the second flight of the Epsilon (Epsilon-2), the solid-propellant launch vehicle, and obtained the significant data from the lift-off through the end of flight safety range. One notable difference from liquid-propellant H-IIA/B is its on-board environment. Epsilon’s second stage, where RINA is installed, rotates at the maximum of 1 Hz on roll axis to stabilize its attitude. We adopted new algorithms which can continuously acquire and track positioning satellites even during spin motion.
There were other issues particular to the Epsilon. When the Epsilon spins on roll axis, velocity error is produced because Doppler frequency shift is affected by antennas’ rolling. Velocity error is also generated by tracking delay of Frequency Lock Loop (FLL) because each antenna in spin motion cannot constantly acquire and track GNSS signals. Likewise, position error occurs due to tracking delay of Delay Lock Loop (DLL). Therefore, we adopted other algorithms to RINA, which can reduce these position and velocity errors. The results of RINA’s accuracy and stability were satisfactory. The new tracking system will become operational from the late 2017. This paper describes the new GNS tracking method in launch vehicle spin motion and the results of RINA’s accuracy in the spin motion using the actual flight of the Epsilon-2.