Oy vey! So many orbit models. Here's another one.
Largely based on Howard Curtis' excellent text, Orbital Mechanics for Engineering Students, second edition. Contains the minimum components needed to model and propagate restricted two-body orbits, with time values leveraging the core Python module datetime.
Primary components (modules) of the package are as follows:
Defines conversions between various anomalies.
Defines earth parameters and key earth-specific calculations (ECF/ENU frame conversions, latitude/longitude, GMST, etc.).
The heart of the oyb package; these module contents are imported with the top package-level oyb object. Contains orbital models and conversions.
Contains various plotting methods (both main plot functions and their specific rendering and annotation behaviors) for Orbit-derived objects in 2d (i.e., ground track) and 3d (i.e., orbital) plots.
Defines vector rotation (lower case) and frame tranformations (upper case). Both transformations can be concatenated to be performed in right-to-left upon a given vector operator. Note that the dot() method must be used, since these functions return a 2d numpy.array object.