Estimating the thermally induced acceleration of the New Horizons spacecraft

Residual accelerations due to thermal effects are estimated through a model of the New Horizons spacecraft and a Monte Carlo simulation. We also discuss and estimate the thermal effects on the attitude of the spacecraft. The work is based on a method previously used for the Pioneer and Cassini probes, which solve the Pioneer anomaly problem. The results indicate that after the encounter with Pluto there is a residual acceleration of the order of ${10}^{-9}{\mathrm{m}/\mathrm{s}}^2$, and that rotational effects should be difficult, although not impossible, to detect.

Figure 1

Model of the New Horizons used for the analysis, showing the antenna, main body, and RTG.

Figure 2

Artistic view of the New Horizons (adapted from [14]).

Figure 3

Distribution of the eight times sixteen Lambertian sources on the RTG (only sources in the upper half are shown). The object on top is a part of the high gain antenna, illuminated by the displayed radiation sources.

Figure 4

Distribution of the sixteen Lambertian sources (represented by the arrows) on the top wall of the main body (only half of the wall is shown due to symmetry).

Figure 5

Resulting probability distribution for the thermal acceleration in the $Y$ direction at the time of encounter with Pluto, overlaid with the derived normal distribution.

Figure 6

Exponential fit of the thermal acceleration along the $Y$ axis, and the $2\sigma$ confidence region around it, for a 20-year period after launch. As a note, Pluto was encountered after a nine-year trip. The dots represent data from Ref. [11].

Figure 7

Euler angles ($\psi$ not shown) transforming the inertial reference frame $x$, $y$, $z$ into the spacecraft’s reference frame $X$, $Y$, $Z$. Euler frequencies are also shown. On the left both $z$ and $\dot{\nu }$ are directed outwards. The same is true for $Y$ on the right. See the text for details.