ADCS.orbits.helpers.orbit_factory module

ADCS.orbits.helpers.orbit_factory.create_random_circular_orbit(radius_km, dt, tf, J2000=0.22, fast=False, rng=None, zonal_J=2)[source]

Creates an initialized Orbit object based on a random circular orbital state.

This function utilizes create_random_circular_os() to generate the initial conditions \(\mathbf{R}\) and \(\mathbf{V}\). It then initializes the orbit propagator.

The end time is calculated as:

\[t_{end} = t_{start} + t_{f} \cdot C_{sec2cent}\]

where \(C_{sec2cent}\) is the conversion factor from seconds to centuries.

Parameters:

  • radius_km (float) – The orbital radius in kilometers.

  • dt (float) – The simulation time step in seconds.

  • tf (float) – The total simulation duration in seconds.

  • J2000 (float) – The start time in J2000 centuries. Defaults to 0.22.

  • fast (bool) – Flag to enable fast propagation mode (reduced precision).

  • zonal_J (int) – Highest zonal harmonic degree to include. 0 disables zonals, 2 includes only J2, and larger values include every zonal term up to that degree.

  • rng (Generator | None)

Returns:

The fully initialized orbit object.

Return type:

Orbit

ADCS.orbits.helpers.orbit_factory.create_random_circular_os(radius_km, J2000=0.22, ephem=None, rng=None)[source]

Generates a random orbital state for a circular orbit with a specified radius.

The position vector \(\mathbf{R}\) is generated by sampling a random vector \(\mathbf{x}\) from a standard normal distribution \(\mathcal{N}(0, I_3)\) and normalizing it to lie on the unit sphere, then scaling by the radius \(r\):

\[ \begin{align}\begin{aligned}\hat{\mathbf{r}} = \frac{\mathbf{x}}{\|\mathbf{x}\|}\\\mathbf{R} = r \cdot \hat{\mathbf{r}}\end{aligned}\end{align} \]

The velocity vector \(\mathbf{V}\) is generated by creating a random tangent direction. A second random vector \(\mathbf{v}_{rand}\) is sampled and projected onto the plane tangent to \(\hat{\mathbf{r}}\):

\[ \begin{align}\begin{aligned}\mathbf{v}_{tan} = \mathbf{v}_{rand} - (\mathbf{v}_{rand} \cdot \hat{\mathbf{r}}) \hat{\mathbf{r}}\\\hat{\mathbf{v}} = \frac{\mathbf{v}_{tan}}{\|\mathbf{v}_{tan}\|}\end{aligned}\end{align} \]

The magnitude is set to the circular velocity \(v_{circ}\):

\[ \begin{align}\begin{aligned}v_{circ} = \sqrt{\frac{\mu}{r}}\\\mathbf{V} = v_{circ} \cdot \hat{\mathbf{v}}\end{aligned}\end{align} \]
Parameters:

  • radius_km (float) – The orbital radius in kilometers.

  • J2000 (float) – The current time in J2000 centuries. Defaults to 0.22.

  • ephem (Ephemeris, optional) – Optional ephemeris object. If None, a new one is created.

  • rng (Generator | None)

Returns:

The generated orbital state.

Return type:

Orbital_State