[Difx-users] [Non-DoD Source] Re: generate fixed JPLEPH calc9 file for calcif2? {External} {External} {External}

[Walter Brisken]

Hi Jan,

This is great.  If you can point me to a copy of the ephemeris file I 
can update the calcServer in gitlab.

Cheers,

Walter

On 1/28/25 01:25, Jan Wagner wrote:
> Hi David,
>
> interesting to hear about the internals, esp. that the record lengths 
> of DE403 and DE421 are identical. Apparently, data structures are, 
> too. I did not expect DE403/DE421 files to be interchangeable in terms 
> of structure.
>
> "Can you try the calc9 server as is using DE421?" --> Indeed, that 
> fixed it! Wow.
>
> Now VLBI track m25020 of 20th January 2025 works under calcif2. As 
> does a copy of m25020 shifted to year 2045.
>
> The steps were:
>
> cd $DIFXROOT/share/CalcServer/
> cp $DIFXROOT/share/difxcalc/DE421_little_Endian .
> mv JPLEPH DE403_little_Endian
> ln -s DE421_little_Endian JPLEPH
> startCalcServer
>
> It's a bit ridiculous that it was actually that simple! :P
>
> Many thanks again!!
>
> Kind regards,
> Jan
>
> On Thu, Jan 23, 2025 at 9:33 PM Gordon, David CIV USN NAVOBSY DC (USA) 
> <david.gordon126.civ at us.navy.mil> wrote:
>
>     Jan,
>
>     The record lengths (8144 bytes) appear to be the same for DE403
>     and DE421.
>     I put together a short program using the relevant subroutines from
>     the calc9
>     version of cpepu.f and ran it with the DE421 ephemeris. It ran
>     with no problems.
>     DE421 seems to be good up to Jan. 2, 2050. Can you try the calc9
>     server as is
>     using DE421?
>
>     If that doesn't work I think I can make a new DE403 file with data
>     from 1900
>     to 2100. I think JPL may have made some changes in DE403 since I
>     originally
>     made a binary version around 26+ years ago. I recall ascii files
>     being in chunks
>     of 25 years. Now they are 100 years. And the record length may
>     have been
>     7144 bytes. John Benson may have made the file you have sometime later
>     with the larger record lengths. Or whatever. Let me know how
>     things go.
>
>     David
>
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