5
$\begingroup$

So, usually a few days after every launch, I go out and check out the published TLE data for each satellite, made public courtesy of CelesTrak. It generally includes all the orbital parameters for each satellite, and more importantly, the rocket body, as I like to see how accurately SpaceX places their payloads into the predetermined orbits.

However, for the launch of DSCOVR, no TLE (or more correctly, an incomplete TLE) has been published for either. Plugging in the International Designators for DSCOVR and the Falcon 9 R/B (which are 2015-007A and 2015-007B, respectively) into the SatCat search form, which I acquired from the raw SatCat database here (warning, large text file), returns this:

No TLE found

Furthermore, this is reflected on the n2yo.com tracking site, which does not show any orbital path for DSCOVR or the Falcon 9 R/B.

  • Why is this? Is it simply a case of the TLE having not been published yet, or will they not publish it as it is beyond Earth's SOI (which is not technically true, the Falcon 9 R/B is in Earth orbit still).

  • If they don't track objects beyond Earth's SOI, how does one follow their orbital positions?

Improve this question
$\endgroup$
0

2 Answers 2

Reset to default
10
$\begingroup$

TLEs are (as far as I know) only issued for Earth-orbiting spacecraft. Since DSCOVR is placed in L1 and not in a near-Earth orbit that's probably why its TLE are missing. I checked for TLEs of SOHO and ACE, which are also placed in L1, and SatCat gives the same output.

P.S: The fact that there's no TLEs does not mean that the spacecraft is not tracked. TLEs are just a type of low-precision ephemerides (+ something else such as information on the orbital lifetime) kindly issued by NORAD to the general public. There's more options to retrieve spacecraft position and velocity, such as HORIZONS.

Improve this answer
$\endgroup$
7
  • 2
    $\begingroup$ However, as I say, there should at least be a TLE for the Falcon 9 R/B which is in Earth orbit. $\endgroup$
    – marked-down
    Feb 17, 2015 at 16:58
  • $\begingroup$ Yes, I have no idea about the Falcon 9 R/B actually. Perhaps it will re-enter soon, therefore they decided not to release its TLEs? I don't know enough about its orbit to make a guess. $\endgroup$
    – LeWavite
    Feb 17, 2015 at 17:08
  • 1
    $\begingroup$ I honestly have no idea about which spacecraft are tracked in HORIZONS and which are issued TLEs and what's the relation between the two databases. My Two-Line-answer is: "TLEs were not issued for DSCOVR because it is not in Earth orbit". As for the Falcon 9, I guess that the R/B was the stage which re-entered and tried the landing on their drone ship, i.e. it could not be in orbit anymore. The second stage should still be there, but probably not in Earth's orbit anymore. $\endgroup$
    – LeWavite
    Feb 17, 2015 at 17:19
  • 1
    $\begingroup$ Falcon 9 R/B is the second stage, and should still be in Earth orbit. $\endgroup$
    – marked-down
    Feb 17, 2015 at 17:29
  • 3
    $\begingroup$ R/B stands for "Rocket Body" and is designated NORAD Catalog Number only if it reaches orbit, so that would be F9 upper stage. As it injected DSCOVR towards SEL1, it will end up in a heliocentric orbit at an altitude below 1 AU. BTW, your "Two-Line-answer" in the comment is good, but I'm not sure it's apparent or properly supported in the answer. If you wanna go with "TLE are only issued by NORAD for tracked object orbiting the Earth, which neither DSCOVR nor FALCON 9 R/B will", that would be an answer then. For DSCOVR you already say that, but not also for FALCON 9 R/B. ;) $\endgroup$
    – TildalWave
    Feb 17, 2015 at 17:30
4
$\begingroup$

I realize this is an old question, but in case someone stumbles across it (as I just did):

It is true that TLEs for 2015-007B = DSCOVR booster are not provided by Space-Track. However, that object (and others in high Earth orbits) are occasional annoyances for the astronomers looking for near-earth asteroids, and they've imaged 2015-007B many times over the last four years. From these data, I've computed orbital elements and fitted TLEs :

https://www.projectpluto.com/pluto/mpecs/pseudo.htm

https://github.com/Bill-Gray/tles/

The file '15007b19.tle', for example, contains TLEs covering 2019 for this object. 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.

Improve this answer
$\endgroup$
1

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.