Spectral response functions (SRFs) and MW passbands
Spectral response functions for VIS/IR coefficient files
All coefficient files for a particular instrument (e.g. those based on different predictor versions) use the same SRF data.
The channels for each instrument are listed in the coefficient file order. You can confirm the RTTOV channel order by looking at the coefficient file headers or by using the rttov_coef_info.exe tool.
The README_SRF section is copied from the coefficient files at the top of each page linked below. For instruments with both IR-only and VIS/IR coefficient files the README_SRF sections from both coefficient files are copied when they are not identical.
Spectral response data for MW coefficient files
Full spectral response function data are available for a small selection of microwave sensors. The corresponding optical depth coefficient files include “_srf” in the filenames.
Pass band data for MW coefficient files
Most MW coefficient files are based on “top-hat” (or “box-car”) spectral responses. These are defined in filter files.
Key for MW pass band filter files:
Two records for each channel
Fields in record 1: channel, polarisation, no-of-offsets, bandwidth (MHz)
Fields in record 2: central frequency (GHz), offset1 (GHz), offset2 (GHz)
(1) Polarisation – this refers to the treatment of surface emissivity:
0: Average of vertical and horizontal polarisation i.e. 0.5(H+V)
1: Nominal vertical at nadir rotating with view angle QV
2: Nominal horizontal at nadir rotating with view angle QH
3: Vertical V
4: Horizontal H
5: +45 minus -45 (3rd stokes vector) S3
6: Left circular – right circular (4th stokes vector) S4
7: Uneven, fixed, channel-specific mixture of V and H
0: one passband channel
1: two sideband channel
2: four sideband channel
(3) Bandwidth is for each passband
Note the files below are plain ASCII.