time series with sparse em axes

[Molinaro, Marco]

Thanks Markus, Baptiste, Ada (direct email),

indeed I should look better into the time series Note.

The doubt that I still have (that applies also when
using the dynamic-spectrum as the datatype) is about
the user experience (at the obscore/epncore discovery
stage) when they see a spectral axis ranging 237-2695MHz
but actually getting back what are actually multiple
1D, single frequency, time series (time axis is sampled
uniformly, no troubles there), sparsely distributed over
the range band.

I do trust applications to read correctly the FITS bintables
(or whatever other format we might come up), but I wonder
if the sparse em would be confusing.

Since it's not an urgent matter, if we (local group)
progress on this by the time of June, I might try to
provide a quick report there.

Thanks again!
Cheers
    Marco

Il giorno mar 25 mar 2025 alle ore 12:25 Baptiste Cecconi via semantics <
semantics at ivoa.net> ha scritto:

> I Marco,
>
> if I understand well, you have 3 dynamic-spectra (each having 6 spectral
> channels).
> The http://www.ivoa.net/rdf/product-type#dynamic-spectrum data product
> should applicable.
>
> In epncore, this should be no problem to describe the spectral axis.
> Nothing prevents to have sparse spectral axes in the datasets.
>
> Cheers
> Baptiste
>
>
> Le 24 mars 2025 à 09:47, Markus Demleitner via semantics <
> semantics at ivoa.net> a écrit :
>
> Hi Marco,
>
> On Fri, Mar 21, 2025 at 06:26:59PM +0100, Molinaro, Marco via semantics
> wrote:
>
> for a "heritage data" project we have a set of observations
> that consist of time series of nearly monochromatic RHCP & LHCP
> radio fluxes of the full disk Sun.
>
> Unfortunately the files they are stored in (FITS bintables)
> contain:
> - the 6 individual observational frequencies, sparse from 237Mhz to 2.7GHz
> - for each of them 3 time series: LHCP, RHCP and the sum of them (full
> flux)
>
> This leads us to describe them, no matter if in obscore or epncore,
> as 6 separate time series records referencing the same FITS dataset,
> because we are unable to describe the sparse "em" axes.
>
>
> Well, as long as the time axis is sampled uniformly, there is nothing
> that would keep you from having just one time series with 18 columns,
> and I believe clients like SPLAT would do a reasonable job displaying
> them.
>
> If the time axis is not sampled uniformly over all frequencies, I
> think I'd go for per-frequency time series with one column each for
> the three observation modes.
>
> All that is based on what I think will make this data easy to work
> with with generic VO tools, completely independently of the
> underlying physics and in particular community practice.  Therefore:
>
> Or maybe Radio, HE, TD IGs have some insight on this.
>
>
> I'd frankly ask Solar System first (and its vice chair already
> confesses he can't help here).  I'd say *if* there's some dominant
> practice in the community, whatever format that calls for is what I'd
> serve up by default; and then I'd attach a datalink that yields
> SDM-compliant tables with Ada blocks (:-)
> <http://ivoa.net/documents/Notes/LightCurveTimeSeries/index.html>
> for interoperability beyond that community.
>
> Consider this as not much more than my 2 cents, though.
>
>        -- Markus
>
>
>

-- 
Marco Molinaro
INAF - Istituto Nazionale di AstroFisica
Osservatorio Astronomico di Trieste
email marco.molinaro at inaf.it
tel. [+39] 333 33 20 564 [also Telegram]
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