Comments on other ObsCore parameters : s_fov (From Alessandra, Vincenzo and Marco)

[Bonnarel]

From Alessandra, Vincenzo and Marco

In the draft IVOA Obscore Extension for Radio data Version 1.0 s_fov is defined as “A typical value for the field of view size … λ/D where λ is the mid value of the spectral range and D is the diameter of the telescope or the largest diameter of the array antennae or telescopes.” This appears in contrast with the ObsCore definition: “The s_fov column (1D size of the field of view) contains the approximate size of the region covered by the data product. For a circular region, this is the diameter (not the radius). For most data products the value given should be large enough to include the entire area of the observation; coverage within the bounded region need not be complete, for example if the specified FOV encompasses a rotated rectangular region. For observations which do not have a well-defined boundary, e.g. radio or high energy observations, a characteristic value should be given.” The former is in fact computed by means of the mid value of the wavelength range, while the latter is computed by means of the maximum value of the wavelength range. Also, we note that for low frequency aperture arrays whose stations are composed of dipole antennas the diameter D could not be given simply as a dish size but may be defined as a function of the number of dipoles, geometry, etc.

[Bonnarel]

From Alessandra, Vincenzo and Marco This appears in contrast with the ObsCore definition: “The s_fov column (1D size of the field of view) contains the approximate size of the region covered by the data product. For a circular region, this is the diameter (not the radius). For most data products the value given should be large enough to include the entire area of the observation; coverage within the bounded region need not be complete, for example if the specified FOV encompasses a rotated rectangular region. For observations which do not have a well-defined boundary, e.g. radio or high energy observations, a characteristic value should be given.”

From François Bonnarel : this definition is loose enough that the mid value could be also valid. The resulting point to discuss would be "what we need this value for"; then we can decide which definition we take in our radio case;

[Bonnarel]

From Alessandra, Vincenzo and Marco This appears in contrast with the ObsCore definition: “The s_fov column (1D size of the field of view) contains the approximate size of the region covered by the data product. For a circular region, this is the diameter (not the radius). For most data products the value given should be large enough to include the entire area of the observation; coverage within the bounded region need not be complete, for example if the specified FOV encompasses a rotated rectangular region. For observations which do not have a well-defined boundary, e.g. radio or high energy observations, a characteristic value should be given.”

From François Bonnarel : this definition is loose enough that the mid value could be also valid. The resulting point to discuss would be "what we need this value for"; then we can decide which definition we take in our radio case;

From Baptiste Cecconi :

The radio extension of ObsTAP already includes s_fov_min s_fov_max, which is good. For compatibility and consistency with other services, the s_fov should be filled with the "representative" value. I mean, that it is the value, that the provider considers as most representative as possible of the fov value. The provider should have a good idea of the typical value that a user would use to filter data.

[Bonnarel]

This issue has now been solved by a new text for s_fov in #46