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

[Phillips, Chris (S&A, Marsfield)]

Hi all

Sorry I have been on leave so this may be late/irrelevant.

I don’t understand the motivation to try and update calcServer. Surely moving to difxCalc is easier and much better use of effort.

For the ocean loading etc, if telescopes are mussing, why not just add them. There is a European (from memory) webpage which uses the same software to compute these values for arbitrary position.

Though having said that my memory is I failed to successfully add the new values to the tables which come with difxcalc.

It would be great if someone who knows how to do this could add some notes to the diff wiki (or readthedocs).

Cheers
Chris

On 29 Jan 2025, at 01:17, Walter Brisken via Difx-users <Difx-users at listmgr.nrao.edu> wrote:


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<mailto: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 I think JPL may have made some changes in DE403 since I originally
made a binary version around 26+ years ago.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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