This directory contains the pure-Python "sgp4" library by Brandon Rhodes,
vendored for offline orbit propagation.
Source:  https://github.com/brandon-rhodes/python-sgp4  (version 1.4)
License: MIT
Modification: the TLE-validation `assert` statements in io.py were replaced with
equivalent `raise ValueError` statements (to satisfy the QGIS plugin security
scanner, which flags `assert`). Behaviour is unchanged. Otherwise unmodified.
