[Difx-users] Convention for DELAY, WET, DRY Polynomials {External} {External} {External}

[Adam Deller]

Confirming what Geoff said. But also adding that near field models can
already be computed and stored in the im file by difxcalc by installing
SPICE and providing TLEs via the v2d file - having an alternative to SPICE
would be great, but just wanted to make sure you were aware that an option
is already there.

Cheers,
Adam

On Thu, 2 Oct 2025 at 06:28, Geoffrey B. Crew via Difx-users <
difx-users at listmgr.nrao.edu> wrote:

> Unless something has changed, DiFX looks at the DELAY polynomial which
> includes the WET and DRY components which are provided for reference.
>
> I had to reverse engineer this for the ALMA case where an
> atmosphere-included Calc was used for the ALMA array.   The tool
> calcifMixed.py (mpifxcorr/utils) was developed to do the subtraction.
> It worked very well in the ALMA case so I presume it was done
> correctly.  You may wish to review that script.
>
> On 10/1/25 4:04 PM, Joe Skeens via Difx-users wrote:
> > Hi all,
> >
> > I've been working on a routine that replaces the difxcalc
> > interferometric model with the near-field delay model given in
> > https://doi.org/10.1007/s00190-018-1217-0 using precise ephemerides
> > for satellite positions, and I have a question related to how the
> > polynomial models should be formulated in the .im file.
> >
> > Should the DELAY polynomial include the atmospheric delays in the DRY
> > and WET polynomials, or should the DELAY polynomial be purely
> > geometric, with the DRY and WET polynomials being added to the DELAY
> > polynomial during correlation?
> >
> > Thanks,
> > Joe
> >
> > _______________________________________________
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> > Difx-users at listmgr.nrao.edu
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>
> --
> Geoff Crew
> MIT Haystack Observatory
> gbc at mit.edu
>
> _______________________________________________
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>


-- 
!=============================================================!
Prof. Adam Deller
Centre for Astrophysics & Supercomputing
Swinburne University of Technology
John St, Hawthorn VIC 3122 Australia
phone: +61 3 9214 5307
fax: +61 3 9214 8797
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