Spectral response functions

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.

If you have information on updates or corrections to any of the spectral response functions please let us know either on the RTTOV forum or via the NWP SAF Helpdesk.

(A)ATSR

ABI

AGRI

AHI

AMI

ASTER

AVHRR

CLIM

ECOSTRESS

EPIC

FCI

GMS IMAGER

GOES IMAGER

GOES SOUNDER

HIRS

HRIR

IIR

INSAT-3D(R/S) IMAGER

INSAT-3D(R/S) SOUNDER

IRAS

IRMSS

LI

  • MTG 1 LI – SRFs cannot be published due to licence restrictions

MBFIRI

MERSI-1

MERSI-2

MERSI-LL

  • FY-3E MERSI-LL – SRFs cannot be published due to licence restrictions

MERSI-3

MERSI-RM

METIMAGE

MI

MODIS

MRIR

Earth-CARE MSI

Sentinel-2 MSI

MSUGS

MSUMR

MTSAT IMAGER

MVIRI (IR channels)

MVIRI (VIS channel)

MVISR

OLCI

OLI

NASA SBG

SEVIRI

SGLI

SIRS

SLSTR

SSH

OceanSat SSTM

THIR

TIRS

TM

TRISHNA-TIR

VIIRS

VIMS

VIRR

VISSR

VTPR


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)

  Notes
  (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

  (2) no-of-offsets
         0: one passband channel
         1: two sideband channel
         2: four sideband channel

  (3) Bandwidth is for each passband

If you have information on updates or corrections to any of the spectral response functions please let us know either on the RTTOV forum or via the NWP SAF Helpdesk.

Note the files below are plain ASCII.