This module computes the zodiacal emission as a function of wavelength from the zodiacal model of John Good (IPAC's ISSA Expanatory Supplement, May 1994)

The RA, Dec, and UT are read from the FITS file header. From these, the effect of varying solar elongation is computed (valid between elongations of 60 to 120 degrees as observed by IRAS).  For solar elongations outside of 60-120 degrees, the Good Zodiacal Model has been compared to the predicted model flux and Zodiacal Infrared Project (ZIP) data which looked to within 22 degrees of of the Sun at 10 and 20 microns.  They show excellent agreement in shape with some calibration scale discrpancies.

If the input file is an ISO observation, the following keywords should already be present in the FITS header in order to run Zodiacal:
INSTRUME Instrument used
TREFUTC1 UTC (whole seconds since 01-01-1989)
TREFUTC2 UTC (remaining fraction of second)
INSTRA Reference instrument RA (deg) J2000
INSTDEC Reference Instrument DEC (deg) J2000

If the input file is not an ISO observation, the following keywords must be present in the FITS header in order to run Zodiacal:
TELESCOP Telescope used
INSTRUME Instrument used
DATE Date of observation  (CCYY-MM-DD)
RA RA (deg) of observation (J2000)
DEC DEC (deg) of observation (J2000)
UT UT time of observation in HH:MM:SS.SS
EPOCH Epoch of RA, DEC must be set to 2000

Use the Header editor from the top of the ISAP main window to add or change these keywords in the header to the correct format.

By selecting an aperture in zodiacal (LWS, SWS, NONE, or aperture diameter), the zodiacal model computes the zodiacal emission and converts from surface brightness to flux density.

The IRAS offset correction refers to the four offsets (one per IRAS band) used in the Good Zodiacal Model and described in its documentation.  If these offsets are assumed to be physical, a blackbody fit can be made to them.  If "IRAS Offset" is selected, this blackbody fit to the offsets is added to the calculated zodiacal emission.  Typically, these offsets only contribute an additional 10-20% integrated flux across the range of 1-200 microns.  We recommend only using "IRAS Offsets" when working with IRAS data.

Upon exiting the zodiacal module, the zodiacal emission is added to the original spectrum and stored as an AAR in "Stored Datasets".