From jskeens1 at utexas.edu Wed Oct 1 16:04:24 2025 From: jskeens1 at utexas.edu (Joe Skeens) Date: Wed, 1 Oct 2025 15:04:24 -0500 Subject: [Difx-users] Convention for DELAY, WET, DRY Polynomials {External} Message-ID: 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: From gbc at mit.edu Wed Oct 1 16:26:59 2025 From: gbc at mit.edu (Geoffrey B. Crew) Date: Wed, 1 Oct 2025 16:26:59 -0400 Subject: [Difx-users] Convention for DELAY, WET, DRY Polynomials {External} {External} In-Reply-To: References: Message-ID: <9bd0e8c7-be18-4b13-a0e9-0a9b8fed984e@mit.edu> 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 > > _______________________________________________ > Difx-users mailing list > Difx-users at listmgr.nrao.edu > https://listmgr.nrao.edu/mailman/listinfo/difx-users -- Geoff Crew MIT Haystack Observatory gbc at mit.edu From adeller at astro.swin.edu.au Wed Oct 1 21:21:12 2025 From: adeller at astro.swin.edu.au (Adam Deller) Date: Thu, 2 Oct 2025 11:21:12 +1000 Subject: [Difx-users] Convention for DELAY, WET, DRY Polynomials {External} {External} {External} In-Reply-To: <9bd0e8c7-be18-4b13-a0e9-0a9b8fed984e@mit.edu> References: <9bd0e8c7-be18-4b13-a0e9-0a9b8fed984e@mit.edu> Message-ID: 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 > > > > _______________________________________________ > > Difx-users mailing list > > Difx-users at listmgr.nrao.edu > > https://listmgr.nrao.edu/mailman/listinfo/difx-users > > -- > Geoff Crew > MIT Haystack Observatory > gbc at mit.edu > > _______________________________________________ > Difx-users mailing list > Difx-users at listmgr.nrao.edu > https://listmgr.nrao.edu/mailman/listinfo/difx-users > -- !=============================================================! 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 !=============================================================! -------------- next part -------------- An HTML attachment was scrubbed... URL: