Communication-centric Spacecraft Design Optimization Tool and its Application to the Lunar Relay Satellite Design

The process of spacecraft design is highly complicated and often requires in-depth trade studies that involve a large number of variables in vast search spaces. Leading factors such as payload, technological capabilities, and trajectory, to name a few, are traded against costs. It is highly desirable to have a design tool at the early conceptual phases that could lead to an optimal design of the system and prevent unforeseen setback, cumbersome mission operations, or budget overrun. In this paper, we propose a communication-centric spacecraft design optimization tool, to be used at the beginning of the spacecraft design phases, to assess the design performance based on communication metrics. The considered tool takes into account the dynamic geometry of the spacecraft, either an orbiter or a landing asset, along with the planetary ephemeris and spacecraft telecom systems to calculate the telecom metrics of interest to optimize the design. Key spacecraft design parameters will be quantified from the communication perspective by the proposed tool, including optimal aperture size, the need of a gimbal mechanism for the antenna, and the required transmitting power, etc. In addition, the tool can optimize the overall layout of the spacecraft antennas, the solar panels, and other onboard instruments. Simulations from the proposed tool can suggest where the appropriate devices can be placed to ensure constant and unobstructed view. It can point out possible risks of the maneuvers in order for the spacecraft to maintain the desired position by identifying how frequently and how elaborately the spacecraft must be oriented. Preliminary work has been implemented for a future lunar relay satellite to be launched no later than 2020 to provide relay communication service to a human base stationed in the Southern Polar region. Discussion on how the tool can align the design parameters with the lunar infrastructure communication needs and how the antenna should be oriented, includi- ng pointing strategy will also be presented.