To satisfy the requirements that LBTO data archived and distributed to partners be IVOA-compliant, a WCS was
added to MODS headers at the end of April 2022. MODS data taken on and after 2022-04-29 UT will contain a
spatial WCS with keywords [units]: CTYPE1,2; CRPIX1,2 [pixels]; CRVAL1,2 [degrees]; and the CD matrix [degrees/pixel].
For example, for a recent standard star spectrum, the newly added keyword/values were:

CTYPE1 = ‘RA—TAN’
CTYPE2 = ‘DEC–TAN’
CRPIX1 = 4146.056910569106
CRPIX2 = 1586.024390243902
CRVAL1 = 327.7956677256269
CRVAL2 = 28.86362331864455
CD1_1 = -3.4166666666666E-05
CD1_2 = 0.0
CD2_1 = 0.0
CD2_2 = 3.41666666666666E-05

The decision was made to emulate the WCS in LUCI data, which is also a spatial WCS regardless of whether the data are
imaging and spectroscopic. Before any offsets are made, the values of CRPIX1, CRPIX2 represent the pixel coordinates (x,y)
and the values of CRVAL1, CRVAL2 represent the sky coordinates (ra, dec) at the pointing origin. RADEC offsets will change
the CRVAL1,2 values and DETXY offsets will change the CRPIX1,2 values. The updatepointing command will redefine the current
CRPIX1,2 values as the pointing origin. The CRVAL1,2 values may be helpful when stacking dithered spectra or when interpreting
pseudo-IFU observations where an extended object is dithered across the slit.

Please note, however, that with the addition of a spatial WCS, users may encounter warnings or problems during
the reduction of spectroscopic data:
* With IRAF, at the final stage of extracting a spectrum using apall, there is a warning “Warning: Coordinate system
ignored (rotated?). Using pixel coordinates.” This is harmless and can be ignored.
* The WCS causes problems in the wavelength calibration step of the modsIDL pipeline, and the WCS keywords may need to be
stripped. (Thanks for the report on this).

Please let us know of any warnings or errors encountered when using other tools (pypeIt or another pipeline) to
reduce MODS data with the newly added WCS.