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Envisat - SCIAMACHY: New Level 1b dataset version 8 available

06 May 2016

The Level 1b re-processing campaign of the full Envisat-SCIAMACHY mission (from 02/08/2002 up to 08/04/2012) has been completed with the instrument processor version 8.

The re-processed data (SCI_NL__1P) are made available to the user community for direct download via the ESA centralised dissemination service (DissHarm). The previous dataset (Level 1b version 7.04) will remain available until further notice at the D-PAC archiving centre on the eoa-dp.eo.esa.int server (login credentials remain unchanged).

Access to SCIAMACHY products can be provided through ESA Fast Registration.

Users already having access to SCIAMACHY Level 1b data can retrieve the details for the new account on DissHarm via the "My Online data" area (on the My Earthnet pages) using their dedicated SSO credentials.

The new Level 2 full mission reprocessing campaign (version 6.01), using as input the new SCIAMACHY Level 1b version 8 dataset, is currently on going with an expected data release of end 2016.


Level 1b version 8 processor upgrades

The following algorithm changes have been implemented in the Level 1b version 8 processing baseline, compared to earlier version 7 data:

  • The stray light matrix approach is extended to channels 3-8 leading to an improved stray light correction
  • The memory effect correction (MEC) for limb data is improved, correcting the estimate for the signal of the reset readout at new tangent heights. This is especially significant for measurements above 40 km tangent height.
  • The scaling factor used for the non-linearity correction (NLC) for co-added data is corrected. In the previous version the NLC was wrongly calculated, when PMD signals were affected by high noise.
  • The hot pixel correction for limb dark measurements is completely revised leading to more reliable results
  • The polarisation correction for occultation is switched off, since no reliable calibration data exist for this case, and since no significant amount of polarisation is expected in this mode
  • The states used for the dark calculation can now be selected in the configuration file. This is important for channel 8. In the previous Level 1b product version 7.04 only dark states with pixel exposure times between 0.125 and 1 second are used.
  • The radiometric calibration uses a new approach: a physical model of the scanner unit including contamination layers (the scan mirror model)
  • The radiometric key data and the polarisation key data are updated from on-ground calibration data and adapted for the scan mirror model
  • The degradation of the transmission is calculated using the scan mirror model that provides a scan angle dependent degradation correction. The degradation is now corrected in the Level 1 processing via m-factor application as part of the radiometric calibration.
  • The mean PMD values contained in the product are now degradation corrected
  • Use of a database, in place of auxiliary data files, for the in-flight calibration parameters derived from calibration measurements

More information on SCIAMACHY can be found on the SPPA website.


Re-processed Level 1b dataset

The SCIAMACHY consolidated Level 1b version 8 dataset is the result of the latest ESA full-mission reprocessing campaign, completed in 2016. The new dataset represents the first complete reprocessing after the conclusion of the in-flight phase of the Envisat mission; it brings significant improvements to the quality of the Level 1b products with a new approach to compensate the instrument degradation.

The reprocessed dataset covers the whole operational mission lifetime period, from 2 August 2002 up to 8 April 2012.

SCIAMACHY Level 1b version 8 products are identified by the fields reported in the table below. More than one software version and processing centre are indicated, as corrective delta processing was necessary to generate the full-mission dataset.

MPH Field Value
Processing stage flag Y
Processing centres DPA
IMF
Software versions SCIA/8.01
SCIA/8.02

Users of SCIAMACHY Level 1b products are strongly recommended to migrate to the new reprocessed version 8 dataset.


Product format and tools

According to the new product specifications, the file format of the new Level 1b products has been updated and it is available online. Size and structure of the ASCII headers (SPH Data Set Descriptors) have been revised to reflect the usage of the new calibration database in place of auxiliary data files.

The Basic Envisat Atmospheric Toolbox (BEAT) and related software have been updated accordingly, allowing fields' extraction and data handling. Latest versions of the tools are: BEAT v.6.9.1, VISAN v. 3.11.0 and CODA v. 2.16. In order to use CODA with the SCIAMACHY Level 1b version 8 data, a new CODA definition file ENVISAT_SCIAMACHY-20140916.codadef specifying the new format, has to be used.


SciaL1c Software

A new version of the SCIAMACHY Calibration and Extraction Tool (SciaL1c 3.2) has been developed to calibrate the Level 1b version 8 products and is now available to the users. The SciaL1c tool incorporates new features adjusted to needs of the next Level 1b-2 processing baseline (SGP version 6.01). In particular, it applies a new hot pixel mask detection algorithm and was adjusted reflecting the modified calibration scheme: degradation and etalon correction is now performed in the Level 0-1 processing step via m-factors (previously during Level 1-2 processing). Executable files as well as complete documentation can be found here.


Documentation

More detailed information on all changes implemented for the reprocessing campaign with baseline version 8 is available on the ESA Sensor Performance, Products and Algorithms portal.

  • Products Quality Readme File: ENVI-GSOP-EOGD-QD-16-0140, issue 1.0
  • Algorithm Theoretical Baseline Document (ATBD): ENV-ATB-DLR-SCIA-0041 issue 6
  • Products Specifications: PO-RS-MDA-GS-2009 volume 15 issue 3M
  • Input / Output Data Description (IODD): ENV-TN-DLR-SCIA-0005 issue 8