[Difx-users] generate fixed JPLEPH calc9 file for calcif2? {External} {External}

[Walter Brisken]

Hi DiFX'ers,

My hope is that a simple fix (replacing the number "5000" with a bigger 
number) in CALC5Server.c will cause things to work again. If anyone is 
in a position to try this and report back that would be great.

The data file in question is derived from the JPL ephemeris but is in a 
format that only calcserver reads.  I am not sure how to recreate that 
file.  Folks wanting to correlate well into the future should probably 
develop a plan to move to difxcalc11.  In addition to the current issue, 
I have found that compiling "RPC" based code is getting less easy.  Red 
Hat Enterprise Linux has demoted the libtirpc-devel package to a second 
tier repo.

The ocean loading in difxcalc11 is easy to update, but the system is 
still indexed by station code which is fragile.  I would propose 
changing that to indexing on station position (X,Y,Z) with some 
tolerance (maybe 100m or so).  It would be a bit of work to do this, but 
once done it would simplify long term maintenance. Another thought, 
which would be of value to those with new or "non-standard" stations or 
those wanting to experiment with different ocean loading coefficients, 
would be to allow supplying a file that would take precedence or fill in 
gaps over the default ocean loading values.

Indeed John Benson has long since retired.

-Walter

On 1/21/25 07:47, Jan Wagner via Difx-users wrote:
> Hi list,
>
> the old CALC 9.1 model behind DiFX 'calcif2' comes with two data 
> files, JPLEPH and Horizons.lis.
>
> Unfortunately, the file JPLEPH file is "broken" in the sense that the 
> ephemerides data contained in it ended already on 12th January 2025.
>
> For VLBI experiments after that date, the calcif2 processing needed 
> prior to correlation does not work - not even for VLBI experiments 
> without local planetary objects.
>
> Perhaps someone on the list would be able to generate a corrected file?
>
> John Benson created the current file at NRAO more than 10 years ago. 
> Unfortunately, he is not at NRAO anymore, perhaps retired.
>
> A move to difxcalc11 to replace calcif2 is possible, but the ocean 
> loading tables in it are incomplete. They are missing a lot of 
> stations, difxcalc11 complains. It'd be more convenient if calcif2 
> could work for a while longer - with a fixed JPLEPH file.
>
> Many thanks,
> kind regards,
> Jan
>
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