[Radioig] Comments on ObsCore extension and Pulsar/FRB draft documents {External} {External}

[John Tobin]

Hi Baptiste,

The 75 percentile uv distance is not a generic value, but could be 
calculated for each dataset. I get your point that dense core arrays 
will have fewer outlier baselines, but the density of uv points will be 
such that the beam one gets from imaging a dataset would be more 
reliably characterized by something like the 75th percentile baseline 
rather than the max uv distance. I think there would be value in min, 
max, and something in between like 75th percentile.

Best,
John

On 1/31/23 02:55, Baptiste Cecconi wrote:
> Hi John and François,
>
> I discussed with my colleagues from NenuFAR (ALan on CC)
>
>>> 3. uv_distance_max, uv_distance_min; This might not quite be fine-grained enough because you might have one really long baseline and one very short baseline, but an array is actually configured somewhere in between. Perhaps also adding a 75th percentile baseline and 50th percentile baseline distance would be useful to add to this since those values would provide more information about where most of the uv-coverage is concentrated.
>>>
>> Good point, we were already wondering how to estimate "effective numbers" for these two quantities in order to avoid "outliers". Your percentile is an interesting proposal to investigate. Or can we find another significant minimum and maximum estimation ?
> Well, for dense-core arrays, there might be very few "outlier" baselines, but those are a very significant addition to the core. Hence, we (NenuFAR team) would like to keep the min and max values as they are. Remember that this metadata should be filled for each observations, hence those values should contain the actual baseline min and max values for an observation, not a generic value for the instrument. Since we are building data discovery metadata, the uv coverage keywords should be consistent with each shared dataset.
>
> Sincerely
> Baptiste

-- 
John Tobin
Scientist
Science Ready Data Products (SRDP) Project Scientist
National Radio Astronomy Observatory
jtobin at nrao.edu
+1-434-244-6815