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SciaL1C Command-line Tool

The SCIAMACHY Calibration and Extraction Tool SciaL1c is an application provided to the users of the SCIAMACHY Level 1b products. This application allows users to select specific calibrations to apply to Level 1b data, which are in the case of SCIAMACHY defined as not fully calibrated Level 0 channel information in combination with calculated calibration data. The generated Level 1c products are suitable for the user's particular applications.

What is SciaL1c?

  • Calibration and extraction tool for SCIAMACHY Level 1b data
  • Command-line based utility
  • UNIX-like syntax, e.g. SciaL1c –option1 –option2   L1b-product-name
  • Batch processing allowed

SciaL1c was initially part of the EnviView software package (discontinued), and became independent as stand-alone software since its release version 2.1. Note that the SciaL1c tool provided with EnviView shall no longer be used, as it is out of date with respect to the processing baseline.

Major changes and improvements in Version 3.2 with respect to Version 2.1

SciaL1c Version 3.2 is designed to process SCIAMACHY Level 1b version 8 products.

  • M-Factor and etalon corrections are applied within the Level 0-1 processing step for the new Level 1b version 8 baseline, therefore a warning is printed out, and the calibration step is skipped, if the user tries to re-apply these corrections with SciaL1c.
  • Etalon and m-factor options result obsolete for Level 1b files of version 8 and must not be used.
  • For Level 1b version 8 products a Fractional Polarisation sign change is implemented for all measurement types whereas for version 7 products and lower versions it was applied only for limb and occultation types.
  • A new hot pixel detection algorithm by Sander Slijkhuis has been implemented.
  • New option –compat with appropriate parameters allows forcing etalon and m-factor calibrations, and the processing of lower product versions.
  • Since etalon correction is already calculated in, –cal all and –allcal no longer include this type of calibration.
  • In case one state fails, processing of other states is now continued.

See the SciaL1c Software Release Notes for a complete listing of all changes.

System Requirements
SciaL1c version 3.2 is available for the following platforms:

  • Linux on x86 (i686-pc-linux-gnu)
  • Linux on amd64 (x86_64-pc-linux-gnu)
  • Windows (i686-pc-windows)


What can the SciaL1c tool do?
A complete description of the SciaL1c functionalities can be found in the SciaL1c Software User's Manual.
Features include:

  • List all measured states on a Level 1b product
  • Extract data sets from a Level 1b product – selecting on:
    • measurement time
    • geolocation
    • data set type (e.g. Nadir, Limb, Monitoring)
    • refined selection options within a data set (see below)
  • Perform Level 1b to Level 1c processing:
    • apply all default calibrations, or
    • apply only specified calibrations.


Selection options within a data set:

  • Extract data containing a specific SCIAMACHY Measurement Category
  • Extract data from user-specified clusters (i.e. spectral ranges, this requires knowledge of the SCIAMACHY cluster configuration available from SOST website.
  • Extract PMD measurements
  • Extract fractional polarisation values.


Selection of Calibrations
The following calibration options exist:
No calibration – do not apply any calibration step (DEFAULT)
0 =  memory - application of memory effect (channel 1-5) and non-linearity (channel 6-8)
1 =  leakage - application of dark signal correction
2 =  ppg -  application of Pixel-to-Pixel Gain
3 =  etalon - application of etalon correction (channels 1-5).  Since etalon correction is already applied to the new Level 1b version 8 products, the calibration step is skipped selecting –cal all and –allcal. Option compat permits to force usage of etalon correction.
4 =  straylight - application of stray-light correction
5 =  spectral - application of wavelength calibration
6 =  polarisation - application of polarisation correction
7 =  radiance - application of radiometric calibration
8 =  sun - PMD sun normalisation
mfactor =  mfactor - application of M-factor file. Since degradation correction is already applied to the new Level 1b version 8 products, the calibration step has to be forced with the new compability option.
all =  allcal - application of all calibrations (0-8 but etalon)

References

Download
Executable files (Version 3.2, Revision 6) can be downloaded here


Installation and Syntax Example
The SciaL1c software is provided as binary executable file. It only requires to be copied into an appropriate path on your platform (for example /usr/bin or some other convenient path which is set in your PATH variable), and to be started launching the scial1c command with proper options (or you may alias to the installation path and tool name with an alias name).
Syntax examples are provided within the Software User's Manual. As an example, to select and fully calibrate all Nadir and Limb data (measurement categories 1 and 2) in SCIAMACHY channel 3, select option: –cat 1,2 –nadircluster 17,18,19,20,21,22,23  –limbcluster 13 –allcal

Input Data
SciaL1c version 3.2 is designed in accordance with the SCIAMACHY operational processing for Level 1b baseline version 8. A sample Level 1b version 8 product is made available here

SCI_NL__1PYDPA20020802_193334_000060272008_00157_02215_0000.N1 (316 MB)

md5sum 6f74ff1bd2105ee965933bd3844ba1bc

The entire SCIAMACHY Level 1b version 8 dataset, resulting from the latest full-mission reprocessing campaign completed in 2016, is available to users via Fast Registration. Details are available here.

M-Factors are used for the correction of instrument degradation affecting the light path. Starting from SCIAMACHY Level 1 processing baseline version 8, m-factors are already applied to the Level 0-1b processing step and enclosed into the Level 1b products. The external input of M-factor files (provided by the University of Bremen is thus no more required.