Simultaneous Orbit Determination for Spacecraft and Its Target Asteroid from Onboard Relative Measurements

The purpose of this study is to establish a new method for simultaneous orbit determination of a spacecraft and its target asteroid in the solar system only using onboard relative position measurements. The measurement system includes an onboard laser ranging sensor or other means to measure the range, an onboard telescopic optical navigation camera or other means to measure the relative bearing between the spacecraft and its target asteroid, and star sensors installed on the spacecraft to measure its inertial attitude. Gravitational interaction between the spacecraft and its target asteroid is considered and contributed to their orbit determination with the simultaneous mass estimation of the asteroid. Conditions for local weak observability of the simultaneous orbit determination system are obtained and mathematically proved. Observability-based modified unscented Kalman filter are designed and used as simultaneous orbit determination algorithms. Simulation results illustrate the performance of the developed navigation algorithms in comparison with the original unscented Kalman filter. .