[Radioig] voltage UCD?

Fri Mar 31 13:40:43 CEST 2023

> From: Markus Dolensky <markus.dolensky at uwa.edu.au>
> Date: Fri, 31 Mar 2023 08:16:47 +0000

Hi Markus Do & others,

> Hi Markus De., Francois, Mireille,
> 
> @Markus De: 
> We are talking about raw (calib_level = 0), complex voltage data (o_ucd =
> stat.fourier?) from a future radio interferometer that records them in near
> realtime (dataproduct_type = timeseries).

Correct me if I'm wrong, but I think what you're really talking about
is "I/Q data" that describes the in-phase (I) and quadrature (Q)
components of a (downmixed) signal.  The I and Q components are often
combined in a single complex number but that really is just a
mathematical convenience.

Note that reconstruction of the original signal (which is presumably
what is needed/wanted in the subsequent analysis) you need to know the
frequency of the mixer signal (LO) that was used to construct the I
and Q components.

> So yes, stat.fourier is a possible candidate. I will try to source an
> opinion from one of the Pulsar astronomers designing the data product.

The existence of stat.fourier.amplitude suggests that stat.fourier
would indeed be complex number; but the I/Q representation isn't
really a fourier transform of the original signal...

Is a new UCD "atom" that indicates I/Q data appropriate?  With the
understanding that this would be a complex number?  Not sure if there
is a need to have a UCD that represents the indivicual I and Q
components.

> I have taken note of the UCD maintenance process.
> 
> @Francois
> re ObsCore extension and ADU: 
> Likewise, I'm following up with the pulsar team on the nature of the voltage
> data. Timezone difference suggests that won't happen before next week.
> 
> @Mireille
> Thanks a lot for jump-starting the RFM. 
> 
> @All
> Depending on said internal clarifications, we may or may not propose
> something new. Given that the respective data product does not yet exist,
> there is no particular urgency and no shortage of uncertainty.
> 
> For now, thanks for the great considerate responses!
> Markus
> 
> Markus Dolensky
> Technical Leader
> International Centre for Radio Astronomy Research
> The University of Western Australia | M468, 35 Stirling Highway | Perth WA
> 6009
> T +61 8 6488 5072
> 
> On 30/3/2023 22:33, Mireille LOUYS wrote:
> 
>  Hi Markus , hi radio astronomers, 
> 
>  I think we can discuss the definition of a new term, if the requirement
>  is to label a measurement corresponding to some voltage. 
> 
>  The current procedure for UCD addition is to prepare a short document to
>  explain the context for adding a new term.
>  This can be done in a short file called VEP-UCD.
>  I have prepared such a file , as included here below.
> 
>  The first step is to discuss the detailed information of the VEP, and
>  the group can finalise the requirement for this UCD :
> 
>  here is my proposal , to be completed by your inputs as
>  radioastronomers. 
> 
>  ----  starts of: VEP-UCD-012_voltage------
>  Vocabulary extension proposal for UCDs / 
>  Vocabulary: UCDlist 1.6
>  Author: mireille louys for radio interest group
>  Date: 2023-03-29
> 
>  New Term: phys.voltage
>  Action: Addition
>  Label: Voltage (measured by an instrument)
>  Prefix: Q
>  Description:  Voltage quantity 
>   
>  Relationships: can be combined with instr.param for observing
>  configuration
>  Rationale: 
>  Radio data in raw format can measure a voltage quantity as signal,
>  before the data is calibrated.
>  'phys.voltage' can be used as well to identify a parameter of the
>  observation configuration used with an instrument.
> 
>  Discussion:
>  To be completed by radio and semantics WG remarks
>  Pros and cons ...
>  Other existing ucd terms that can be used instead...
> 
>  Response: (To be completed by UCD board after discussion)
> 
>  ----  end of VEP-UCD-012_voltage------
> 
>  When we agree, this can be added on the RequestForModificationPage here:
>  https://wiki.ivoa.net/twiki/bin/view/IVOA/UCDList_1-6_RFM
> 
>  many thanks for your inputs to finalise this first step.
> 
>  cheers , Mireille
> 
>  Le 30/03/2023 à 13:21, Markus Demleitner a écrit :
> 
>  Hi Markus,
> 
> On Tue, Mar 28, 2023 at 06:30:55AM +0000, Markus Dolensky wrote:
> 
>  Can somebody suggest a UCD for complex voltage data, please?
> 
> Context is the Obscore o_ucd for PSRFITS data.
> 
> Hm... it would seem nobody has an immediate solution, and reviewing
> the current UCD list make me suspect there's nothing remotely
> matching -- although I have to admit that I've no clue of PSRFITS...
> Does what you'd like to annotate have a complex part because of phase
> information in a fourier transform?  If so, perhaps stat.fourier
> could remotely work?
> 
> With that caveat, I suppose the Right Thing™ to do would be to
> propose a new UCD.  This is less of a hassle than it might sound like
> -- see
> https://ivoa.net/documents/UCDlistMaintenance/20191007/REC-UCDlistMaintenance-2.0-20191007.pdf.
> 
> However, I suppose it would be a good idea to discuss the RFM here
> first before handing it over to Semantics.
> 
>          -- Markus
> 
> -- 
> --
> Mireille Louys,  MCF (Associate Professor)  
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