obs_subaru's support for processing data from SuprimeCam has not been exercised since its successor HSC went on the sky, and at this point it's so bitrotted that reviving it would probably involve copying all of HSC's configuration and mapper files and modifying them again after just throwing away the relic SuprimeCam ones (or at least a line-by-line diff of the two). The SuprimeCam camera geometry may still be relevant - though it's unlikely to still be compatible with the afw cameraGeom interfaces.

Regardless, any work we would do to revive SuprimeCam support would work as well if the bitrotted files we have on master today were accessible only through git history. We have nothing to gain by keeping them on master.

We don't have a lot to lose by keeping them on master, but there is a cost, and I believe it exceeds the cost of removing them. We have a lot of configuration split between the config and config/hsc directories, making it harder to read and maintain, even though the distinction is entirely hypothetical. And just having dead files in the package makes it more work to browse and grep the live ones (which I was trying to do recently on DM-24485). It also contributes to obs_subaru's idiosyncratic organization (which we have already approved fixing on RFC-508 but never implemented).

This RFC proposes that we simply remove (with no deprecation period; that's just extra work here, because we know no one is using this stuff) all SuprimeCam-only files from obs_subaru, and begin to consolidate - when convenient and backwards compatible, not on a triggered ticket for this RFC - any config files or classes split up only so they could be used by SuprimeCam as well as HSC.

The reorganization proposed on RFC-508 would be amended to just put HSC files directly under lsst.obs.subaru instead of lsst.obs.subaru.hsc (as many are already there, this makes it less disruptive than the original RFC-508 proposal). As in that RFC, that reorganization would require a deprecation period, and I'd like to continue to consider it the implementation of RFC-508, not this one.

This change would make it logical to rename obs_subaru to obs_hsc, but I am definitely not proposing that: the entire premise of this proposal is that removing SuprimeCam files won't break anything or otherwise be disruptive, and renaming the package absolutely would.