FOV File Structure

26AUG22 web-page reformatted
Contents

Overview

The Field-of-View (FOV) represents the spatial convolution function Φ (in the vertical domain) applied to the pencil-beam input spectra τ(z) by the HIROS (or HSDI) instrument, so that the convolved transmittance τ0 reported at nominal (boresight) tangent height z0 actually represents

τ0 = ∫ τ(z) Φ(z-z0) dz

The FOV is tabulated as Φ(zi-z0) on an arbitrarily-spaced vertical grid, monotonically increasing in altitude. An arbitrary scale factor is assumed, eg setting maximum value Φ=1, but the end-values of the tabulated FOV must be 0.

The FOV files used within the Cubemap E2E simulator, for both HSDI and HIROS, are a particular case of the RFM .fov file format.

To specify a δ-function FOV, use '*' instead of the FOV filename in the MORSE driver file

Example: hiros.fov, which can be read with IDL function read_fov.pro

File Structure

The file contains a header section consisting of an arbitrary number of initial comment records followed by a single record containing a single number: the number of tabulated points.

This is followed by the list of altitudes, spread over as many records as required, then, starting with a new record, the tabulated FOV function, also extending over as many records as required.

All numerical data are read 'free-format'.

Header Section
!CMNT Comment record(s) (optional)
NAlt No. of tabulated values
Altitude Data
Alt(1) Alt(2) ... Block of NAlt numbers
... Alt(NAlt)
FOV Data
FOV(1) FOV(2) ... Block of NAlt numbers
... FOV(NAlt)

Data Dictionary

Field Type Description Units Range
!CMNT String*80 Comment record first character is '!'
Alt Float(NAlt) Altitude relative to nominal tangent point km
FOV Float(NAlt) FOV relative response at Alt(i) [1] ≥ 0 expected
NAlt Integer No. tabulated data points [1] ≥ 3

Notes

  1. At least three points must be specified with FOV(1) = FOV(NAlt) = 0 to define vertical extent of FOV response.

Document Changes

26AUG22 This web-page reformatted
25JUL22 Original