Warning: This code is experimental; please see the LICENSE.
An
SGP4
implementation based on
github.com/aholinch/sgp4/tree/master/src/c,
which ultimately 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 NORAD ID
20413 at mins=1844335,
where 1e-07 < rdist < 1e-06. The tests have been edited to tolerate
rdist < 1e-06 rather than demand rdist < 1e-07.
The main constructor is NewTLE(), and the primary method is
Prop(). See ExampleProp() in
surface_test.go.
See the documentation for details.
The example command-line program sgp4go reads TLEs
from stdin and writes propagation data to stdout. See
test.sh for an example invocation.
Some sgp4go executables are available
here.