Presentation of the CATDS : Description of the SMOS L3 Products Generation and Dissemination
Guibert, Sarah1; Tarot, Stéphane2; Cabot, François3; Hourcastagnou, Jean-Noël1; Larigauderie, Carole1; Kerr, Yann3; Reul, Nicolas2; Boutin, Jacqueline4

The CATDS (Centre Aval de Traitement des Données SMOS) is the french ground-segment facility in charge of the generation, calibration, archiving and dissemination of the SMOS science products level 3 and level 4. It processes Ocean Salinity (OS) and Soil Moisture (SM) products. CATDS is also a centre providing services to users and scientists.
Therefore, it is in charge of:

  • Processing of the SMOS level 3 and 4 science data from level 1B data received from the ESA Data Processing Ground Segment (DPGS),
  • Re-processing of the SMOS level 3 and 4 data,
  • Catalogue and storage of the level 3 and 4 products, including the auxiliary data, the calibration data, and the level 1B data used for the processing,
  • Calibration and validation of the SMOS L3 and L4 products,
  • Dissemination of the SMOS level 3 and level 4 products to the users,
  • Assistance and support to SMOS L3 and L4 users,
  • Potential feedback towards DPGS (new algorithms, calibration functions, and software).

    CATDS is split in two main types of components:

  • a C-PDC (Production Centre) which routinely produces and disseminates L3 and L4 data from L1B and auxiliary data. It is located at SISMER (IFREMER) in Brest.
  • 2 C-EC (Expertise Centre) which host the algorithms definition, which assess the quality of the products and which provide specific information to users. These two C-ECs are located at CERSAT in Brest (C-EC dedicated to Ocean Salinity) and at CESBIO in Toulouse (C-EC dedicated to Soil Moisture).

    The CATDS processing chain to generate SM and OS L3 data from L1B products is composed of several processors. Some of them (L1C and L2 processors) are based on the ESA DPGS's prototypes. The main difference with level 2 processes is that DPGS processing is based on half an orbit, whereas CATDS processing is based on several days of data. On the SM side per example, the CATDS L2 processor takes into account several revisits simultaneously, and this once per day.
    One of the goal of the CATDS L3 processors is to select correct input data and to reject the dubious ones. These L3 processors perform temporal analysis, time aggregations and spatial and temporal averages.
    The L3 products generated and distributed by CATDS are the following:

  • 1 day global map of soil moisture values (daily aggregation of SMOS orbits)
  • 3 day global map of soil moisture values
  • 3 day global map of dielectric constant
  • 10 day global map of soil moisture values
  • Monthly global map of soil moisture values
  • 1 day ocean salinity values
  • Average salinity fields (monthly 200km average for the moment, soon extended to 10 day and monthly 25, 50, 100 and 200 km averages).
    CATDS also produces and distributes global map of polarized brightness temperature at ground level (arranged by incidence angle values).

    The C-PDC is operational since the middle of year 2011. The first reprocessing campaign was performed at the beginning of 2012, taking into account more than 2 years of measurements (January 2010 to April 2012). In September 2013 C-PDC will distribute almost 4 years of level 3 SM and OS products. A web site ( describes the products and gives information related to the operational status.

    Users can access the products either through FTP or through the Sipad, an interactive Web based tool which allows aggregations and sub-settings.

    A single point of contact ( operated by the production center allows users:

  • To ask for the FTP credentials
  • To give feedback about the products
  • To obtain support either technical or scientifical on the products and their usage

    We present here the CATDS production centre with a focus on processing chains and on the exploitation status. We also describe the L3 data dissemination process and the way to retrieve CATDS L3 products.