AccelDrag

class ssapy.accel.AccelDrag(recalc_threshold=2592000, **defaultkw)[source][source]

Bases: Accel

Acceleration due to atmospheric drag.

This class uses the Harris-Priester density model, which includes diurnal variation in the atmospheric bulge, but omits longer period seasonal variations.

The acceleration also depends on a drag coefficient, which is hard to determine a priori, but takes on typical values around ~2 to ~2.3 for most satellites.

See Section 3.5 of Montenbruck and Gill for more details.

Parameters:

  • recalc_threshold (float, optional) – Number of seconds past which the code will recompute the precession/nutation matrix. Default: 86400*30 (30 days)

  • defaultkw (dict) – default parameters for kwargs passed to __call__, (area, mass, CR)

Methods Summary

__call__(r, v, t[, _T])

Evaluate acceleration at particular place/moment.

Methods Documentation

__call__(r, v, t, _T=None, **kwargs)[source][source]

Evaluate acceleration at particular place/moment.

Parameters:

  • r (array_like, shape(3, )) – Position in meters in GCRF frame.

  • v (array_like, shape(3, )) – Velocity in meters per second in GCRF frame.

  • t (float) – Time as GPS seconds

  • area (float) – Area in meters^2.

  • mass (flat) – Mass in kg.

  • CD (float) – Drag coefficient. Typical values are ~ 2 - 2.3

Returns:

accel – Acceleration in meters per second^2

Return type:

array_like, shape(3,)