Development and Attitude Disturbance Estimation of Separation Mechanism for Nano Moon Lander OMOTENASHI

OMOTENASHI is a CubeSat that will be launched by a NASA SLS rocket. Its mission is to demonstrate that a CubeSat can make a semi-hard landing on the Moon. The 6U-size spacecraft consists of an orbiting module (OM), a rocket motor (RM) for decelerating, and a surface probe (SP) on the landing module. Its mission will prove successful when the accelerometer mounted on the SP sends its information back to Earth. Under the tight resource constraints, a unique mechanism was designed for separating the RM and SP from the OM, based on small volume and low mass. Its function has been verified through several tests. Moreover, the attitude disturbance at separation in orbit has been estimated by numerical simulation. The nutation angle has been evaluated through spin-drop testing and simulations, and using a correlation model, the nutation angle in orbit and the effect of several error factors have been estimated. Results reveal that the nutation angle is not determined only by the spin rate. The nutation before separation predominates at lower spin rates in determining the nutation angle of the RM after separation. This paper presents the design overview, test results, and attitude estimation.