An
SGP4
implementation based on
github.com/aholinch/sgp4/tree/master/src/c,
which ultimated originated with David Vallado.
This file contains the sgp4 procedures for analytical propagation
of a satellite. the code was originally released in the 1980 and
1986 spacetrack papers. a detailed discussion of the theory and
history may be found in the 2006 aiaa paper by vallado, crawford,
hujsak, and kelso.
companion code for
fundamentals of astrodynamics and applications
2013
by david vallado
(w) 719-573-2600, email dvallado@agi.com, davallado@gmail.com
This implementation is a hand-edited transpilation of C
sources to Go by
c2go (version v0.25.9
Dubnium 2018-12-30), and the emitted code was edited by hand. The
original C implementation test suite was included in this process.
The substantive edits (of Go sources emitted by the transpiler) were the use of 64-bit integers to address at least one 32-bit overflow and using floating point constants instead of naked integer constants when the entire expression consisted of the latter with some division. Example: "var x2o3 float64 = 2 / 3" was edited to be "var x2o3 float64 = 2.0 / 3.0".
With those changes, the original (transpiled and hand-edited) tests almost all pass. The one exception is for objectNum 20413 at mins=1844335, where 1e-07 < rdist < 1e-06. The tests have been edited to tolerate rdist < 1e-07 rather than demand rdist < 1e-06.