Minimize SLSTR Level 1 Processing - Observation Mode Parameters

Eight different auxiliary files are used during SLSTR Level-1 processing:

  • The SLSTR Level-1 Ancillary data file defines the sizes and offsets of the SLSTR ancillary data variables in the ancillary ISP, and lists the calibration functions and parameters that should be applied to each variable. It will be determined during the ground characterisation of the instrument and will be fixed before launch. Additional entries define bit masks and validation limits for the raw data and surveillance limits for calibrated data.
  • The SLSTR Level-1 Visible and Shortwave Infra-Red Characterisation data files define non-linearity correction tables and general calibration parameters for each visible and shortwave infra-red channel. These data were generated during ground calibration of the instrument. There are two netCDF files for each of the S1, S2 and S3 channels (covering the nadir and oblique views), and four netCDF files for each of the S4, S5, S6 channels (covering the two views and the A and B detector stripes).
  • The SLSTR Level-1 Thermal Infra-Red Characterisation data files define radiance-to-temperature Look-Up Tables (LUTs) and non-linearity correction tables, as well as general calibration parameters for the thermal infra-red channels. These data were generated during ground calibration of the instrument. There are two netCDF files for each of the S7, S8, S9, F1 and F2 channels (covering the nadir and oblique views).
  • The SLSTR Level-1 VISCAL data file contains summary visible and shortwave infra-red calibration information derived from the VISCAL solar illumination period, typically for the orbit immediately preceding the current product. Note that this file is produced during operation of the SLSTR Level-1 processor for each orbit.
  • The SLSTR Level-1 Vicarious Calibration data file comprises a table of scaling factors for each VIS-SWIR band (S1-S6) that allows correction for long-term drift. There is a drift correction factor provided for each day of the Sentinel-3 mission. The default values for the scaling factors are set to 1, i.e. no correction to be applied to the data.
  • The SLSTR Level-1 Geometry data file defines the instrument geometry parameters used in the geolocation processing. The transformation matrix between the satellite reference frame and the instrument frame is computed using these parameters (cone angle for each scan, scan inclination for nadir scan) allowing the geographical position of each pixel to be determined.
  • The SLSTR Level-1 Geometry Calibration data file provides the quaternions characterising the biases and thermo-elastic deformation model for nadir and oblique views, defined as rotation from instrument to SC frames. Quaternions are provided for each view, each Julian day and each on-orbit position angle. They are divided into four components, with the first representing the real part of these thermo-elastic deformations.
  • The SLSTR Level-1 Cloud LUT ddata file provides parameters used by the cloud-clearing algorithms. The data are split into several groups, each dedicated to a specific cloud test and providing specific parameters and thresholds.