Talk:Jet Propulsion Laboratory Development Ephemeris

Reason for title move[edit]

The old title misquoted the name -- see the full name (as used in current title) in the following docs originating from JPL itself:

document showing DE96 full name

document showing DE108 full name

Terry0051 (talk) 19:22, 11 May 2009 (UTC)[reply]

Sun moving around a center of mass (barycenter)[edit]

... this is a very interesting effect that our sun is "wobbling" - very slowly - around the barycenter of the planetary system. The "wobbling" can be calculated from the NASA Ephemerides Homepage as well in "xyz" or "observer" coordinates ... It might be interesting to know that this wobbling comprises 2 to 3 diameters of the sun itself (sun's diameter is about 1.5 million km) Kampmann-peine (talk) —Preceding undated comment added 21:03, 30 July 2010 (UTC).[reply]

And also that, since the motion is mostly dominated by Jupiter (more massive than all the other planets combined of course), the inner four planets are affected alike, orbiting the Sun/Jupiter barycenter along with the Sun. Thus their orbits are also moved in ~12-year near-ellipses, by roughly similar amounts, all in step, and the distances among them, as between the Earth and Sun, are perturbed by less. Wwheaton (talk) 02:46, 1 August 2010 (UTC)[reply]

Merging with DE400[edit]

I will be merging this article with DE400 within a few weeks, if there are no objections. Tfr000 (talk) 19:50, 9 January 2012 (UTC)[reply]

Text and/or other creative content from this version of DE400 was copied or moved into Jet_Propulsion_Laboratory_Development_Ephemeris with this edit on 31 January 2012. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists.

So anyway, the merge is done. Someone else might want to elaborate on the History section. In researching the article, I found the following DE/LE (Development Ephemeris/Lunar Ephemeris) referenced, but information on most of them is very sketchy: 19/4, 26, 35, 39, 40/4, 43/6, 45, 61, 69/16, 67, 84, 96, 102/51, 108, 111, 114, 118, 122, 125/125, 130, 140/140, 142, 143, 200/200, 202, and of course all of the DE400 series which I documented in the article. — Preceding unsigned comment added by Tfr000 (talk • contribs) 19:22, 9 February 2012 (UTC)[reply]

Era notation[edit]

In accord with WP:ERA I will make the era notation consistent with the first established notation in this edit. Jc3s5h (talk) 12:51, 31 August 2013 (UTC)[reply]

Text in Distribution section vague[edit]

If " … this precision says nothing about how well the ephemeris describes the actual motions of the planets, … " then how is it possible to use the ephemeris to navigate spacecraft to a planet, which is clearly in motion, and will be at a far different location when the craft is due to arrive ?

" … which is a function of the accuracy of the original observations … "

ah, and those observations would be what where when how ? and how long are these valid ?

" and of the "goodness" of the least-squares fit."

Tasty sounding, but too vague. — Preceding unsigned comment added by 108.248.201.141 (talk) 20:54, 17 November 2015 (UTC)[reply]

I had a go at clarifying; see if it is an improvement. --Mark viking (talk) 23:30, 17 November 2015 (UTC)[reply]

Originally written that way merely to emphasize that it's not necessarily that we know the real position of any planet to 25 meters, for instance. A casual reading of the article might come across like that. We might in fact be able to do something close to that, but that's not what recovering data from the DE does. Tfr000 (talk) 17:28, 21 November 2015 (UTC)[reply]

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