Decide on how/if to support 'SCIENCE_SC' mode (06) data

[DavidT3]

This is part of the filtering and separation that occurs during stage 2 of the nupipeline tool - the premium quality events are demarked as 'SCIENCE' (their Obs mode) or '01' in the shorthand. Of course we shall use them.

What I'm talking about here are the 'SCIENCE_SC' events - so they'll be on-sky rather than occluded by the earth or on the calibration source, but for whatever reason the optical-bench star tracker (which is the best way of defining the aspect solution) isn't available. Thus as a backup the spacecraft bus star trackers are used, but as they are known to undergo thermal flexing, the pointing accuracy degrades to ~2 arcminutes.

So, it might possibly be useful for, say, global measurements of properties from galaxy clusters (with a suitably large region), but less so for point sources or spatially resolved analyses.

I do think that we should include support for the creation of these files, but it seems that adding them to the 01 class events like we would combine sub-exposures in XMM would be unwise.