Maximilian Linhoff

I don't think we should let the legacy behavior of other instruments or software take precedence over the current version of the FITS standard for new iterations of the specification....

@fabiopintore Hi, thank you for making this proposal. Just to note: there is a mechanism in GADF to associate EVENTS to IRFs: the HDU index tables documented here: https://gamma-astro-data-formats.readthedocs.io/en/latest/data_storage/hdu_index/index.html

> Does it mean that for GADF the HDU tables are mandatory? No they are not mandatory in the standard. They are only needed if it is not clear which...

> Although, unless I'm mistaken, HDU index describes "the format" of each IRF component within a file, but does not associate specific events to IRFs. It associates an EVENTS table...

E.g. for the FACT data in the open crab sample: ``` In [4]: t[t['OBS_ID'] == 20131105212] Out[4]: OBS_ID HDU_TYPE HDU_CLASS FILE_DIR FILE_NAME HDU_NAME int64 bytes6 bytes8 bytes2 bytes21 bytes17 -----------...

> I see. I feel current OBS_ID specifications are not clear for the case of an IRF, specially if this is the event IRF association we want. The observation ID...

> For instance: It is expected many instruments will generate separated EVENTS and IRFs as "productions" (and not run-wise) as done by the current generation of IACTs, LAT, and for...

> I feel current OBS_ID specifications are not clear for the case of an IRF, There is currently no `OBS_ID` field for IRFs, there is an issue about this: https://github.com/open-gamma-ray-astro/gamma-astro-data-formats/issues/132...

> What is/could be missing is metadata within the IRF components describing to which events they may be applied to Yes, but this is a much harder problem that depends...

> I think this is not sufficient. The issue came up in the context of updating the Gammapy tutorials to the latest alpha configuration of CTA IRFs. Doing this we...