# poliastro.core.events¶

## Module Contents¶

### Functions¶

 eclipse_function(k, u_, r_sec, R_sec, R_primary, umbra=True) Calculates a continuous shadow function. line_of_sight(r1, r2, R) Calculates the line of sight condition between two position vectors, r1 and r2. elevation_function(k, u_, phi, theta, R, R_p, H) Calculates the elevation angle of an object in orbit with respect to
poliastro.core.events.eclipse_function(k, u_, r_sec, R_sec, R_primary, umbra=True)

Parameters
• k (float) – Standard gravitational parameter (km^3 / s^2).

• u () – Satellite position and velocity vector with respect to the primary body.

• r_sec () – Position vector of the secondary body with respect to the primary body.

• R_sec (float) – Equatorial radius of the secondary body.

• R_primary (float) – Equatorial radius of the primary body.

• umbra (bool) – Whether to calculate the shadow function for umbra or penumbra, defaults to True i.e. calculates for umbra.

Notes

The shadow function is taken from Escobal, P. (1985). Methods of orbit determination. The current implementation assumes circular bodies and doesn’t account for flattening.

poliastro.core.events.line_of_sight(r1, r2, R)

Calculates the line of sight condition between two position vectors, r1 and r2.

Parameters
• r1 () – The position vector of the first object with respect to a central attractor.

• r2 () – The position vector of the second object with respect to a central attractor.

• R (float) – The radius of the central attractor.

Returns

delta_theta – Greater than or equal to zero, if there exists a LOS between two objects located by r1 and r2, else negative.

Return type

float

poliastro.core.events.elevation_function(k, u_, phi, theta, R, R_p, H)

Calculates the elevation angle of an object in orbit with respect to a location on attractor.

Parameters
• k (float) – Standard gravitational parameter.

• u () – Satellite position and velocity vector with respect to the central attractor.

• phi (float) – Geodetic Latitude of the station.

• theta (float) – Local sidereal time at a particular instant.

• R (float) – Equatorial radius of the central attractor.

• R_p (float) – Polar radius of the central attractor.

• H (float) – Elevation, above the ellipsoidal surface.