The attitude of the proposed Asterius spacecraft will be maintained through three-axis stabilization. A trade optimization study was performed for the most common stabilization methods for interplanetary craft: spin, dual spin, and three-axis. The trade equation used in the comparison is given in Equation 2.
| J | = | -2(weight) -1(power) | (2) |
| +3(kick stage) -5(mass properties) | |||
| +4(maneuverability) +3(lifetime) | |||
| +2(payload/scan) +3(pointing) | |||
| -3(propellant) -3(mechanical complexity) | |||
| -1(computer complexity) +6(reliability) | |||
| +5(accuracy) -2(cost) |
Some important considerations and reasoning behind the assigned weighting included the vehicle mass properties. This is in reference to the inertia properties Ixx, Iyy, Izz, or the tendency of the spacecraft to be shaped like a pencil versus a disc shape. Such a consideration will affect the structural design of the spacecraft and the launch vehicle fairing constraints. Maneuverability was a concern due to the stiffness of the angular momentum vector of the spinning craft, which requires a large thrust to reorient.
Mechanical complexity entered the equation as an allusion to the dual spin Spin Bearing Assembly (SBA). The SBA is the interface between the rotor and the stator portions of the spacecraft. It presents a challenge to transfer power and data from one portion of the craft to the other across the SBA. Despite its flawless operation since launch, the Galileo SBA presented numerous obstacles to overcome in its design and fabrication stages. Therefore, the mechanical complexity, in the case of Asterius, was given a significant weighting.
The pros and cons of the stabilization methods were analyzed via the trade optimization study, and resulted in three-axis stabilization being chosen for Asterius. Increasing advancements in technology have greatly improved the implementation and feasibility of three-axis stabilization.