RFM File Formats

.ils File: Instrument Line Shape

11NOV17

Type
Input(s), mandatory if ILS Flag enabled.

Description
(Apodised) instrument line shape function(s)

Filename(s)
Specified in *ILS section of Driver Table

Structure
Files may concatenated
!CMNT [optional comment records]
NPT PT1 PTD [WNOMIN WNOMAX]
ILS(1) ILS(2) ...
... ILS(NPT)
[eof]

Fields
FieldTypeDescriptionRange
!CMNT C*80 Comment record(s) (optional) Record starts with '!'
NPT I Number of tabulated points |NPT| = 2:MAXILP (in rfmsiz.inc)
Tabulated as Fn of Wavenumber [cm-1] NPT >0
Tabulated as Fn of Frequency [GHz]] NPT <0:
PT1 R*8 Relative Waveno/Freq of 1st Point |PT1|<1 (usually negative)
PTD R*8 Waveno/Freq spacing for tabulation (usually positive)
WNOMIN R*8 (Optional) Lower Waveno/Freq for ILS use
WNOMAX R*8 (Optional) Upper Waveno/Freq for ILS use
ILS R*8 ILS Function

Notes
  1. WNOMIN, WNOMAX can be used to specify several ILS files for application over different spectral ranges (eg MIPAS Bands A, AB, B, C, D).
  2. If WNOMIN, WNOMAX are absent, it is assumed the supplied ILS is the default function to be applied over any range not fully covered by one of the specific-range ILS functions (consequently there should only be a maximum of one such ILS in the supplied .ils file(s))
  3. The ILS function has to be tabulated on a regular Wavenumber/Frequency grid. It is best if this is also the internal RFM grid used for the finemesh calculation (usually 0.0005 cm-1) - functions specified on any other grid will be interpolated.
  4. The ILS function does not have to be normalised or symmetric. After interpolation to the internal fine mesh grid it is renormalised.
  5. The maximum ILS width that can be specified is ±1 widemesh interval from the centre (i.e. around 2cm-1 total width if symmetric). This is because the RFM only retains the spectra from one previous widemesh interval for convolution (this restriction is removed for RFM v5)

Example
(note that triangular ILS shapes can be applied more simply using the AVG Flag)
! Triangular ILS for approximating 0.035 cm-1 halfwidth resolution.
! Npts   Lowest Wno   Del.Wno       Applic.Range: Min  Max  (0=any range).
    3      -0.035      0.035                      685  970       
    0  1  0
[eof]