SGP4 - SGP4/SDP4 Orbit Propagator (Spacetrack Report #3)#

Pure OCaml implementation of the standard algorithm for predicting satellite positions from Two-Line Element (TLE) data. Used by NORAD, NASA, and most space agencies.

The algorithm handles:

• SGP4: Near-Earth objects (orbital period < 225 minutes)
• SDP4: Deep-space objects (orbital period >= 225 minutes)

Installation#

opam install sgp4 will install this library.

Usage#

open Sgp4

(* Parse TLE and propagate *)
let tle = parse_tle tle_string in
let state = init tle in
let pos, vel = propagate state minutes_since_epoch

Reference#

• Hoots & Roehrich, "Spacetrack Report No. 3", 1980
• Vallado's improvements (2006)