SRF File Structure

24AUG22: Web-page reformatting
Contents

Overview

The Spectral Response Function (SRF) file contains the spectral response of a single HSDI channel, sampled on a uniform wavenumber grid.

Example: HSDI_01.srf, which can be read with the IDL function read_srf.pro

File Structure

The SRF file consists of a record-structured header section, containing two non-comment records, followed by a data section containing the list of SRF values read as a single block of numbers.

It is similar to the structure of the ILS file, with the addition of the Channel_ID and Wno_Nom fields.

All numerical values are read free-format.

Header Section
!CMNT Comment record(s) (optional)
Channel_ID Channel identifier, left justified, up to 8 characters
!CMNT Comment record(s) (optional)
NWno   Wno_Min   Wno_Del   Wno_Max   Wno_Nom Wavenumber axis parameters, single record
Data Section
SRF(1) SRF(2) ... Data section containing as many records as required
... SRF(NWno)

Data Dictionary

Field Type Description Units Range
!CMNT String*80 Comment records first character is '!'
Channel_ID String*8 HSDI Channel Identifier eg 'HSDI_01'
NWno Integer No. data points ≥ 3
SRF Float(NWno) Tabulated Spectral Response Function [1]
Wno_Del Float Wavenumber increment cm-1 > 0
Wno_Max Float Upper Wavenumber limit cm-1 > Wno_Min
Wno_Min Float Lower Wavenumber limit cm-1 0 – Wno_Max
Wno_Nom Float Nominal Channel Wavenumber [2] cm-1 Wno_Min – Wno_Max

Notes

  1. Wavenumber of tabulated SRF at point iWno given by: Wno = Wno_Min + ( iWno - 1 ) × Wno_Del

  2. Nominal wavenumber Wno_Nom is, in principle, the weighted average of the SRF but is only included as a convenient means of referring to the channel.

Document Changes

24AUG22 Web-page reformatting
01JAN22 Original