Overview of the project

Fundamental Data Records for Altimetry (FDR4ALT) is an ESA project aiming at generating innovative Earth system data records named Fundamental Data Records (basically level 1 altimeter and radiometer data) and Thematic Data Records (basically level 2P geophysical products), in the frame of the European Long Term Data Preservation Program (LTDP+).

These products will be based on the exploitation of measurements acquired by the altimeter and radiometer instruments onboard three remote sensing satellites, ERS-1, ERS-2 and ENVISAT.

The goal is to serve the different communities involved in long term data exploitation over the different Earth surfaces: oceancoastalinland waterice sheetssea ice and atmosphere.

Overview of the FDR4ALT products


ERS-1, ERS-2 and ENVISAT Altimeter and Radiometer dataset have been reprocessed in NetCDF format, based on the best state-of-the-art algorithms/corrections with definition and provision of innovative level-1 and level-2P products including uncertainty information at both levels.



Project Planning

T0 = September 2019

Phase 1 : Processing selection and products definition (completed)

  • Completeness analysis
  • Selection of the algorithms for the FDR & TDP products definition
  • Definition of a validation plan
  • Organisation

Phase 2 : Production and Validation (on-going)

  • Algorithm implementation in the CLS/CNES core system
  • Massive p roduction of the FDR and TDP for the whole dataset (23 years of data)
  • FDR and TDP validation
  • Uncertainty characterization

The Project kicked off on September 2019 and the final meeting was held in Toulouse  in May 2023.

Data Access

The FDR4ALT final products are not available yet and will be released Q1 2024. They will be available on the ESA Earth Online Catalogue.

Test datasets available !

Test datasets are available for users and can be downloaded via FTP :


FTP adress :ftp.cls.fr
Login :FDR4ALT
Password: Sent separately

For each FDR/TDP, 2 full cycles of ENVISAT data are available. They are identical to the official FDR4ALT products. To have the password information to access the FTP, contact fpiras@groupcls.com.

The Product User Guide can be found here : FDR4ALT_Products_User_Guide