meetings - Space Flight Mechanics Committee

shown to dramatically improve the navigation of lunar satellites, libration orbiters, and
Earth orbiting satellites using scalar intersatellite observations. In this paper, LiAISON is
applied to the problem of navigating a crewed vehicle to the Moon. It has been found that
LiAISON observations improve the navigation enough to reduce the number of active
ground tracking stations from six to three.
16:15 AAS Constrained Station Change in GEO Using A Legendre Pseudospectral
13-331 Method
Seung Pil Kim, The Pennsylvania State University; Robert Melton, The
Pennsylvania State University
Relocation of a GEO satellite in minimum time, with attention to collision avoidance, is
considered. The collision avoidance term, incorporated as an integral form in the objective
function, is included by specifying a maximum or minimum radius depending on whether
the transfer is in the east or west-direction. Several east- and west-direction maneuvers are
simulated; all the states are found to be within feasible ranges. Multiple revolutions and
large longitude station change cases are also demonstrated using this method. The transfer
time is found to be only weakly affected by the initial thrust acceleration for the multirevolution
16:35 AAS Optimal Trajectory Design for Aerobraking
13-332 Ling Jiang, Beihang University
Aerobraking is an efficient aeroassisted technique that has been used successfully in recent
Mars missions. However, trajectory design process is complicated yet time consuming with
multiple passes through the atmosphere. A simple but effective design method to make this
process easier is proposed. Firstly, perturbed classic element of orbit analysis is used to
optimize of periapsis selection. After choosing the appropriate initial periapsis, an elaborate
computational aerodynamics-trajectory model is developed to simulate the trajectory.
Simulation results show a significant reduction in the maximum control input and
maximum heat rate. The method here can be used for reference to engineering
16:55 AAS Research and Verification of Multi-frequency Same Beam VLBI Based on
13-333 General TT&C Signal
Lue Chen, Beijing Aerospace Control Center; Ling Jiang, Beihang University;
Geshi Tang, Beijing Aerospace Control Center; Songtao Han, Beijing Aerospace
Control Center ; Mei Wang, Beijing Aerospace Control Center ; Huicui Liu, Beijing
Aerospace Control Center
The method of multi-frequency same beam VLBI utilizing spacecraft general Tracking,
Telemetry and Control (TT&C) signal is proposed in this paper. The mathematical
calculation of the difference phase delay of multi-frequency same beam VLBI is analyzed,
and a method of error model modification of difference phase delay is introduced. Utilizing
the multi-frequency information of the general TT&C signals, the simulation results shows
that, picoseconds level differential phase delay is obtained after delay error model
modification. This could provide reliable measurement technology for the relative
navigation of two spacecrafts in deep space mission.
23 rd AAS / AIAA Space Flight Mechanics Meeting Page 59