Re: [Stellarium-pubdevel] using INPOP and JPL ephemeris

[JBerthier <ber...@im...>]

Hi,

VSOP2013 is the last release of the analytic planetary theory VSOP87. It is easy to use. You can choose to use theseries of the 
elliptic elements (ftp://ftp.imcce.fr/pub/ephem/planets/vsop2013/ephemerides/README.pdf) or the Chebyshev files 
(ftp://ftp.imcce.fr/pub/ephem/planets/vsop2013/ephemerides/README.pdf). The solution (terms of series) covers the time span -4000 
+8000, while the Chebyshev ephemerides covers the time span -4500 +4500. The interest of the solution is that it can be reduced with 
the elimination of terms depending on the required accuracy. All the planetary theories VSOP, INPOP, DExxx are very similar in terms 
of planetary ephemerides.

jerome



On 10/03/2015 12:11 AM, Georg Zotti wrote:
> Dear Theodor,
>
> thank you for the link, I will have a look in the next weeks.
>
> You are right, we are planning to have DE43x as option for advanced users,
> also with the possibility to use the file stored outside Stellarium
> folders (in case you are using it already in other software - no need to
> copy 3GB again ;-).
>
> I haven't read much more than the existence of VSOP2013 or INPOP. Is it as
> easy to use and as complete as VSOP87A and does it cover at least its date
> range, i.e., is it a straightforward exchange? It might be worth thinking
> about using several ephemeris versions...
>
> Kind regards,
> Georg
>
> On Fr, 2.10.2015, 15:20, erazortt wrote:
>> Dear Georg,
>>
>> great to hear that the newest JPL data will be usable! (I assume it will
>> be optional)
>>
>> If you want to cross-check your results using classical computation
>> versus the new IAU computation path I'd be happy if my program would
>> help: http://thaec.rascanu.de/
>> Installation instructions are included. With a Linux environment it
>> should take less than 5min.
>>
>> As a side: Since the JPL DExxx data sets are not exactly small, I assume
>> most of the stellarium users will probably not use the possibility to
>> load these files, and will thus stick with the VSOP87 calculation you
>> are using.
>>
>> Perhaps it would make sense to update to the VSOP2013 series, which like
>> VSOP87 is very small compared to the numerical JPL data and could be
>> used as default. Thus also enhancing the calculation for the bulk of the
>> users.
>>
>> Greetings,
>> Theodor
>>
>>
>> Am 28.09.2015 um 07:07 schrieb Georg Zotti:
>>> Dear Theodor,
>>>
>>> thank you for your offer, but the DE43[01] challenge has been taken,
>>> there
>>> is a branch "socis2015-de430" on launchpad. Stellarium does not use SOFA
>>> and goes the "classical" path without ERA, so maybe your program would
>>> still interest me as it could be a way to check our results.
>>>
>>> So, is your program available somewhere? (plus, please, instructions how
>>> to build, libraries to fetch etc.)
>>>
>>> Kind regards,
>>> Georg
>>>
>>> On So, 27.09.2015, 22:55, erazortt wrote:
>>>> Hi all,
>>>>
>>>> I have seen that there is a SOC2015 project for using new ephemeris
>>>> files.
>>>> Searching though the mailing list it appeared that there is still
>>>> nobody
>>>> doing this job.
>>>> If however there somebody is already someone doing it, do not bother
>>>> reading the rest.
>>>>
>>>> Although I do not have time to contribute myself directly, perhaps I
>>>> could still help out.
>>>> Some time ago I have written a small C++ program of around 1000 lines
>>>> code which uses the CALCEPH library to either read JPL DE43x or
>>>> INPOP13c
>>>> files.
>>>> It uses the IAU sofa library to calculate the needed time scales in a
>>>> cascade: local time->UTC->TAI->TT->TDB and TCB.
>>>> It downloads the current polar motion and calculates the pole and
>>>> origin
>>>> of GCRS and ITRS together with the ERA (earth rotation angle).
>>>>
>>>> It finally extracts the ephemeris using calceph and calculates the
>>>> positions in all reference frames with sofa, taking into account light
>>>> travel and atmospheric conditions.
>>>>
>>>> The code does also download newest values for UT1-UTC, polar motion and
>>>> corrections to the precession and nutation model from IERS and
>>>> corrections to TT from BIPM.
>>>> It uses exclusively the IAU2000/06 calculation path (opposing to using
>>>> sidereal time, equinox and ecliptic).
>>>>
>>>> If you are interested I can provide the source code. As I said, it is
>>>> very short!
>>>> If needed I could also answer questions related to the sofa and calceph
>>>> libraries or more general questions concerning the time scales or the
>>>> IAU calculation path.
>>>>
>>>> Greetings,
>>>> Theodor
>>>>
>>>>
>>>
>>>
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-- 
--- Dr. Jerome Berthier ------------------ Phone: +33 (0)14051 2261 --
     Institut de mecanique celeste            Fax: +33 (0)14633 2834 --
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