uses the focalplane radius from DESIMODEL instead of the hardcoded version in fiberassign

[forero]

This PR fixes bug #452

[forero]

These changes only affect the function targets_in_tiles()

[dstndstn]

Looks fine to me!

[araichoor]

sorry I notice I never hit "send" on a small message I had when you opened the PR.

• I apologize, I don t have time right now to carefully look at that
• though one thing we definitely want to check is that the "default" behavior is not changed (ie it does not change anything for the main survey).

I mention this because I notice that the two radii differ:
with the main branch

>>> from fiberassign.hardware import load_hardware
>>> load_hardware().focalplane_radius_deg
INFO: Loaded focalplane for time stamp 2023-03-22 20:35:13.114490+00:00
INFO: Focalplane has 801 fibers that are stuck or broken
1.65

with this PR:

>>> import desimodel.io
>>> desimodel.io.load_platescale()['theta'].max() 
1.651501393

for instance, I could imagine that this change could break the reproducibility of the fiberassign intermediate products (the TILEID-{targ,sky,gfa,scnd,too}.fits files, where the files generated with this PR would have more targets (larger radius); I guess the assignment will be the same, as those extra targets won t get assigned, but I think we d want to keep an exact reproducibility of everything if possible.

so maybe propagate in the code some argument that would default to the current behavior; don t know if that s trivial or not...

[araichoor]

sorry Jaime for not having been responsive here.
addressing here my own question: I think it s good in terms of reproducibility for the main survey; good!

details:

I ve run fba_rerun --infiberassign $DESI_TARGET/fiberassign/tiles/trunk/011/fiberassign-011946.fits.gz --outdir $OUTDIR, with $OUTDIR:

• main (before this PR): /global/cfs/cdirs/desi/users/raichoor/tmpdir/fiberassign_platescale_fix/main
• branch (ie this PR): /global/cfs/cdirs/desi/users/raichoor/tmpdir/fiberassign_platescale_fix/branch

from a quick look, output files are identical, perfect!

I think the reason is that the targets (sky, gfa, too) are queried in fiberassign.fba_launch_io.py with desitarget.io. read_targets_in_tiles(); and that desitarget function calls desimodel.footprint.is_point_in_desi(), which calls desimodel.geometry.get_tile_radius_deg(); and that function proceeds a bit differently:
https://github.com/desihub/desimodel/blob/d18fc5a7ff0c7f2c9cafee890c8c0858ad524ed2/py/desimodel/focalplane/geometry.py#L34-L43

def get_tile_radius_deg():
    '''Returns maximum radius in degrees covered by the outermost positioner.
    '''
    global _tile_radius_deg
    if _tile_radius_deg is None:
        rmax = get_tile_radius_mm()
        platescale = load_platescale()
        fn = interp1d(platescale['radius'], platescale['theta'], kind='quadratic')
        _tile_radius_deg = float(fn(rmax))
    return _tile_radius_deg

and it returns 1.6280324520485583; which is a smaller radius than both radii mentioned in my previous message (1.65 and 1.651501393).
so the selected targets in the intermediate fiberassign files aren't impacted by this, I think.