OMOTENASHI Trajectory Analysis and Design: Earth-Moon Transfer Phase

抄録

OMOTENASHI is a 6U CubeSat that will be launched in 2019 by the Space Launch System (SLS) with the objective of landing on the Moon. The CubeSat is planned to perform two deterministic maneuvers. The first maneuver (DV1) by gas jet propulsion system transfers the probe from the nominal SLS trajectory to a lunar targeted trajectory. The second maneuver (DV2) is applied by the solid rocket motor before landing to counteract the vertical component of the S/C velocity. The high approach speed at the Moon, combined with large errors induced by the solid motor, requires the probe to approach the Moon with a shallow Flight Path Angle (FPA). If the angle is too steep, expected errors in the DV2 may cause the probe to crash. However, a shallow FPA increases the probability of a Moon-flyby or collision with the local topography. In this paper, we present a design method for Earth-Moon transfer trajectory robust to orbit determination (OD) and DV1 execution errors. First step consists of a grid search to determine the nominal DV1 vector with four candidates obtained. Subsequent error analysis suggests the need for a Trajectory Correction Maneuver (TCM). For the two scenarios of OD error provided by the navigation team, an error analysis was conducted including the TCM. Two realistic OD error scenarios were considered: 30 min or 3 hours of two-way Doppler and range measurement. Error analysis conducted considering TCM shows the need for 3 hours of OD to achieve nearly 100% of transfer success rate.