[Difx-users] DiFX Software for Satellite Data Processing {External}

[深空探测]

Hello,

I hope this email finds you well. I am writing to seek some clarification
regarding the data formats for naifFile and ephemFile, as outlined in the
documentation provided at
https://www.atnf.csiro.au/vlbi/dokuwiki/doku.php/difx/spacecraft.

Following the instructions provided, I installed the SPICE toolkit.
However, I am uncertain about the specific data formats required for
naifFile and ephemFile. The documentation states the following:

naifFile: Path to a leap second kernel file for SPICE. Only used with
near-field correlations.
ephemObject: Name of the object from the ephemFile to be associated with
this source. Only used for near-field correlations.
ephemFile: Path to a planetary ephemeris file for SPICE. Only used with
near-field correlations. bsp or tle files are allowed.

I am uncertain about the specific data formats necessary for naifFile and
ephemFile. Furthermore, I am unable to locate a suitable leap second kernel
file (naifFile) for download, even on the website
https://naif.jpl.nasa.gov/pub/naif/. It appears that no similar files are
available on this site.

As for the ephemFile, I have formatted the J2000 orbital data as follows:

```
2023 01 01 0 0 0.000000 -28493026.434 9141302.129 1433273.020 -242.269000
-3586.377000 5.447000
```

However, upon running the vex2difx command, I received an error indicating
that this format of ephemeris parameters is not supported.

I am unsure where to obtain the naifFile （leap second kernel file）. Could
you kindly provide guidance on these matters?

Thanks for any advice,

De Wu

Leonid Petrov <Leonid.Petrov at lpetrov.net> 于2023年8月29日周二 09:50写道：

> Nihao, De Wu,
>
>    We work on support of satellites as targets in difxvtd, but similar
> to difxcalc, it is still in the experimental phase and substantial
> efforts
> for its testing are needed before we could consider it operational.
> The principal difficulty is not in computation of path delay itself, but
> in development of visibility analysis of VLBI observations of satellites
> that
> is substantially different than visibility analysis of continuum
> targets.
>
> Leonid
>
>
> > On 2023-08-27 19:50, Adam Deller via Difx-users wrote:
> > Hi De Wu,
> >
> > The correlation code itself doesn't know or care about the nature of
> > the source; it just applies delays based on the sampled polynomials it
> > is given.  difxcalc is capable of generating delay models for
> > near-field objects using NASA's SPICE code, however I would caution
> > that this is a rarely used and hence rarely tested mode.  Some
> > (minimal) documentation is given on
> > https://www.atnf.csiro.au/vlbi/dokuwiki/doku.php/difx/spacecraft and
> > the vex2difx page it links to, under the SOURCE block.
> >
> > Cheers,
> > Adam
> >
> > On Fri, 25 Aug 2023 at 18:52, 深空探测 <wude7826580 at gmail.com>
> > wrote:
> >
> >> Dear all,
> >>
> >> I am currently using DiFX-2.6.2 software for my data processing
> >> needs. After employing the 'startdifx' command to generate the .im
> >> files, I have noticed that the generated .im files contain delay
> >> data for radio sources. However, my intention is to process data
> >> from artificial satellites. Given that the positions of artificial
> >> satellites change rapidly, the delay data in the .im files
> >> calculated based on the radio source model might not be suitable.
> >>
> >> In light of this, I am reaching out to inquire whether the DiFX
> >> software includes dedicated modules for handling artificial
> >> satellite data. Specifically, I am curious to know if there is a
> >> provision within the software to calculate delay data in accordance
> >> with the operational mode of artificial satellites. I am assuming
> >> that I would be providing the known orbital data of the satellites
> >> as input.
> >>
> >> Your guidance and insights on this matter would be greatly
> >> appreciated. Thank you in advance for your assistance.
> >>
> >> Best regards,
> >>
>
> >> De Wu
> >
> > --
> >
> > !=============================================================!
> > 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
> > !=============================================================!
> > _______________________________________________
> > Difx-users mailing list
> > Difx-users at listmgr.nrao.edu
> > https://listmgr.nrao.edu/mailman/listinfo/difx-users
>
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