E2E L1B HIROS Structure

14JUN24 Change Noise from (NAlt,NMic) to (NMax,NMic)
Contents

Overview

Level 1B (L1B) files are netCDF format files containing calibrated measurement data (spectra in the case of HIROS). Within the Cubemap End-to-End (E2E) simulator this can be generated either by the Level 1 processing module or by the Instrument Bypass module.

Each file contains the measurements from a single occultation event.

Example: l1b_hiros.nc, which can be read with IDL function read_l1b_hiros.pro

The file was written with IDL procedure write_l1b_hiros.pro

File Contents

Global Attributes
Name Type Value
Title String 'HIROS L1B Spectra'
Created String eg 'Tue Jul 13 16:07:27 2021'
Source String eg 'Created using make_l1b_hiros.pro v13JUL21'
Dimensions
Name Size Definition
NMic 3 Number of different microwindows
NAlt eg 10 Number of different tangent altitudes for scene spectra
NMax eg 1000 Maximum Number of spectral points in microwindow [1]
Variables
Name Type Definition Units Range
Satellite String(*) Satellite ID eg 'Cubemap 1'
Instrument String(*) Instrument ID eg 'HIROS'
Orbit Long Orbit number > 0
Sunrise Byte 1=Sunrise, 0=Sunset 0 or 1
Mic_Lab String(NMic) Microwindow identifier eg 'HIROS_A'
Mic_Npt Long(NMic) No. spectral points in each microwindow [1] 1 : NMax
Mic_Min Double(NMic) Lower wavenumber of each microwindow cm-1 0 – Mic_Max
Mic_Max Double(NMic) Upper wavenumber of each microwindow cm-1 > Mic_Min
Mic_Res Float(NMic) Spectral interval of each microwindow cm-1 > 0
Julian_Day Long(NAlt) Day since 1st Jan 2000 days > 0
Milliseconds Long(NAlt) Milliseconds since midnight ms 0 – 86 400 000
Altitude Float(NAlt) Geometric tangent point altitude [2] km 0 – 100 expected
Alt_Offset Float(NAlt,NMic) Microwindow altitude offset [2] km −1 : +1 expected
Alt_Trend Float(NAlt,NMic) Altitude linear trend during scan [2] km −1 : +1 expected
Alt_Quad Float(NAlt,NMic) Altitude quadratic trend during scan [2] km −1 : +1 expected
Latitude Float(NAlt) Tangent point latitude deg N −90 : +90
Longitude Float(NAlt) Tangent point longitude deg E −180 : +180
Rad_Curve Float(NAlt) Earth radius of curvature in LOS plane km 6300 – 6400 expected
Quality Long(NAlt,NMic) Quality Control flags 0=OK, other values TBD
Noise Float(NMax,NMic) Noise spectrum for each microwindow 0 – 1 expected
Transmittance Float(NMax,NAlt,NMic) Transmittance spectra [2] 0 – 1 expected

Notes

  1. NMax is to allow for the number of points in each microwindow, Mic_Npt, being different. For microwindows where Mic_Npt < NMax, just the elements 1:Mic_Npt of Transmittance and Noise will be filled

  2. It is assumed that the tangent point altitude z varies quadratically with wavenumber ν during the scan according to
    z(ν) = a0 + a1x + a2x2     where     x = (ν - νmid)/(νmax - νmin)     and     νmid = 0.5 × (νmax + νmin)
    Thus x varies from −0.5 to +0.5 across the microwindow.

    In terms of L1B variables, a0 = Altitude + Alt_Offset, a1 = Alt_Trend, a2 = Alt_Quad, νmin = Mic_Min and νmax = Mic_Max.

Document Changes

14JUN24 Change Noise from (NAlt,NMic) to (NMax,NMic)
01JUN23 Remove Mic_Alt(:), replace with Alt_Offset(:,:)
13APR23 Add Mic_Alt, Alt_Trend and Alt_Quad fields. Renumber notes
18OCT22 Change MIC_MIN,MAX to Double Precision
30AUG22 Change NBnd to NMic, & Reformatting of web-page.
16JAN22 Change Rad_Curv to Rad_Curve