Re: Started A "Macintosh Software" Site

From: Dr. T.S. Kelso via Seesat-l <>
Date: Thu, 12 Mar 2020 18:07:40 +0000
Very nice, Gavin! I’m looking forward to checking this out.

In the meantime, I’m adding it to the Satellite Tracking Software Index on CelesTrak (  - TS

Dr. T.S. Kelso

On 2020 Mar 05, at 10:23, Gavin Eadie <<>> wrote:

Jumping back two and a half years .. the "SGP4 propagator that I migrated to Swift" is now available at:

The TLE parsing and SGP4 propagation code usage is described in the file.  The library contains various other astronomical functions for which the documentation is not (yet) fleshed out.  Testing the SatelliteKit library against the sample TLE results in the "Revisiting Spacetrack Report #3" generates identical output to machine accuracy.  Some of that paper's TLEs are pathological, in the sense that they are intended to fail; SatelliteKit fails with those too, though not always in ways I understand (the Orekit library, on which this work was based, does not test those pathological TLEs).

Like many things, this is a work in progress, but I feel it is time to put it out there so it can stand, fall or be ignored on its merits.  The "in progress" parts relate to applying more scaffolding around the core propagation function (related to obtaining and caching file/Internet TLE files, observer azimuth/elevation visibility, eclipse depth, etc) and do not impact the purpose of SGP4, the computation of position and velocity vectors.

On Sat, Jul 22, 2017 at 12:33 AM Gavin Eadie <<>> wrote:
The Orekit library, written in Java, at<> also contains a SGP4 propagator that I migrated to Swift.  This is a work in progress but, if I ever update my simple iOS ISS tracker it will be based on that code.  There’ll be more to say about this work when it gets a little more mature and is published.

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Received on Thu Mar 12 2020 - 13:08:29 UTC

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