This fascinating answer to Why has no TLE been published for the DSCOVR satellite and the Falcon 9 R/B? presents links to custom-made TLEs for the Falcon 9 rocket body that put DSCOVR into orbit, and it includes the following:



The file '15007b19.tle', for example, contains TLEs covering 2019 for this object (the spent Falcon 9 rocket body). Note that for this particular object, an SDP4 TLE cannot be fitted, even though the object is bound to the earth. The 'ephemeris type' byte is therefore set to be 2 ("use SGP4 only") and the TLEs use only the SGP4 propagator. So the TLEs will work in some software that actually follows the full TLE specification and respects the 'ephemeris type' byte... and not in a lot of software that isn't so carefully written.

Looking at the TLE history in the github link I see that the mean motion is something like 0.06 meaning it's in a very distant 16 or 17 day orbit! That means that it is very loosely bound to Earth and that the effects of the Sun and Moon should be quite significant.

Question: Why can't home-made TLEs for the DSCOVR launch booster in orbit around Earth work with SDP4?

For more on SDP4 see

  • $\begingroup$ @RussellBorogove Thanks for the edit. I've been convinced in comments below here that it must be the 2nd stage, so feel free to "go all the way" and call it a 2nd stage here as well. $\endgroup$ – uhoh Jun 27 '20 at 23:30

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