RFM File Formats

.ils File: Instrument Line Shape


Input(s), mandatory if ILS Flag enabled.

(Apodised) instrument line shape function(s)

Specified in *ILS section of Driver Table

All numerical data are read free-format
Files may concatenated
File Header Section
!CMNT Comment record(s) (optional)
NPT PT1 PTD [WNOMIN] [WNOMAX] Spectral axis [valid spectral range]
Data Section
ILS(1) ILS(2) ... Tabulated ILS function, NPT values
... ILS (NPT)

Field Type Description Range
!CMNT C80 Comment record, starting with '!' (ignored)
ILS(NPT) D ILS Function
NPT I Number of tabulated points
Tabulated as Fn of Wavenumber [cm-1] ≥2
Tabulated as Fn of Frequency [GHz] ≤-2
PT1 D Relative Waveno/Freq of 1st Point (usually negative)
PTD D Waveno/Freq spacing for tabulation (usually positive)
WNOMAX D (Optional) Upper Waveno/Freq for ILS use
WNOMIN D (Optional) Lower Waveno/Freq for ILS use
Type: I=Integer; R=Real; D=Double Precision; Cn=character string, length n.

  1. 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.
  2. The ILS function does not have to be normalised or symmetric. After interpolation to the internal fine mesh grid it is renormalised.
  3. WNOMIN, WNOMAX can be used to specify several ILS files for application over different spectral ranges (eg MIPAS Bands A, AB, B, C, D).
  4. 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))

iasi.ils (IASI Gaussian-apodised ILS on 0.001 cm-1 grid)