nfsproc¶

Overview¶

nfsproc accepts target coordinates from the Next-Field-Selector and calculates fiber positions, a field center, and ADC prism positions, correcting for procession, nutation, aberration, refraction, and misalignment as necessary.

Input¶

Arguments¶

seqid: a unique sequence identifier
instrument: a string designating the instrument to be used (desi or proto)
targets: the target catalog used to dial the positioners

Configuration¶

TODO

Output¶

prism: positions for the ADC prisms
center: offset between boresight coordinates and field center
positioner_pos: the table of open-loop positioner coordinates
fiducial_pos: the table of open-loop fiducial coordinates, in FVC pixels
fiber_pos: the table of open-loop fiber coordinates, in FVC pixels
nfs_wcs: expected FITS WCS parameters for the field
nfs_data: miscellaneous parameters associated with the sequence

Return value¶

Either SUCCESS if the the caluculation is successful, or an error message othewise.

Use¶

First, a PML connection must be established:

>>> from DOSlib.PML import dos_connection
>>> pm = dos_connection('PLATEMAKER')
>>> pm.execute('configure')
'SUCCESS'

For this demonstration, load some sample data for the input:

>>> from PlateMaker import test_data
>>> seqid = test_data.seq_id
>>> targets = test_data.targets

Actually execute nfsproc:

>>> pm.execute('nfsproc', seqid=seqid, targets=targets)
'SUCCESS'

The results of the calculations can then be retrieved:

>>> nfs_data = pm.execute('get', 'nfs_data')
>>> fiducial_pos = pm.execute('get', 'fiducial_pos')
>>> center = pm.execute('get', 'center')
>>> prism = pm.execute('get', 'prism')

Details¶

`prismSet`¶

The position angles of the ADC prisms are calculated from the zenith distance and paralactic angle of the pointing.

The calculation is done using a polynomial fit in either tan(zd) or sqrt(tan(zd)).

The python implementation starts in line 51 of https://desi.lbl.gov/svn/code/online/PlateMaker/trunk/python/PlateMaker/obs.py?p=43583

The dervish implementation starts in line 113 of https://desi.lbl.gov/svn/code/online/DervishTools/trunk/desi/etc/desi.tcl?p=43583

Polynomial coefficents come from Steve Kent’s raytrace code, saved in PRISM.par.