`DynamicModel`#

class DynamicModel#

Bases: object

Abstract base class for all force models in the dynamic simulation.

Every concrete force model inherits from this class and implements compute_acceleration(), which returns the non-gravitational or gravitational acceleration contribution for a given spacecraft state and epoch. The equation of motion integrated by the propagator is:

\[\ddot{\mathbf{r}} = \sum_i \mathbf{a}_i(\mathbf{r},\,\dot{\mathbf{r}},\,\mathbf{p},\,t)\]

where each \(\mathbf{a}_i\) is the acceleration contribution from force model \(i\), \(\mathbf{p}\) is the vector of solve-for or consider parameters, and \(t\) is the current epoch.

Sub-classes also expose _compute_partial_by_* methods that return \(\partial \mathbf{a}_i / \partial \mathbf{p}\), the Jacobian of the acceleration with respect to each solve-for parameter. These partials drive the variational equations

\[\dot{\mathbf{S}} = F\,\mathbf{S} + \frac{\partial \mathbf{f}}{\partial \mathbf{p}}\]

whose solution \(\mathbf{S}\) maps parameter uncertainty into state uncertainty and is required by the orbit-determination filter.

Parameters:: None

Notes

Concrete sub-classes must implement compute_acceleration() and optionally _compute_partial_by_position() and the relevant _compute_partial_by_* methods for any solve-for parameters they support.