Modeling the nongravitational acceleration during Cassini’s gravitation experiments

In this paper we present a computation of the thermally generated acceleration of the Cassini probe during its solar conjunction experiment, obtained from a model of the spacecraft. We build a thermal model of the vehicle and perform a Monte Carlo simulation to find a thermal acceleration with a main component of $(3.01\pm 0.33)\times 10^{-9}\mathrm{m}/{\mathrm{s}}^2$. This result is in close agreement with the estimates of this effect performed through Doppler data analysis.

Figure 1

Three-dimensional model of Cassini showing the configuration of the RTGs and their covering structures (1), the spacecraft body composed by a cylindrical lower module (2), a conical upper module (3) and a prismatic main bus (4), and the parabolic high-gain antenna (5).

Figure 2

Detail of the geometric model of the umbrellalike structure covering each RTG.

Figure 3

Probability density distribution resulting from the Monte Carlo simulation of the thermal acceleration along the $z$-axis, with the normal distribution with the same mean and standard deviation superimposed.