Wednesday, February 28, 2024

The Surface Water and Ocean Topography (SWOT) project is pleased to announce the public release of Level 2 Geophysical Data Record products from the onboard nadir altimeter (NALT) and the advanced microwave radiometer (AMR).

This release includes the Geophysical Data Record (GDR) from each of the NALT and AMR instruments. The onboard NALT is a Jason-class dual frequency (Ku/C) altimeter. The onboard AMR is also a Jason-class radiometer but with two active strings that facilitate measurements on the left and right sides of the satellite nadir point.

Product description documents for these products can be found online at:

The datasets in this release include Cycles 400 to 578 (January 15 – July 10, 2023) during the SWOT commissioning and calibration phases (1-day repeat orbit), and Cycles 1-6 (July 21 – November 23, 2023) during the science phase (21-day repeat orbit). Note that some passes are not available in the later portion of cycle 578, and very early portions of Cycles 402 and 1 during orbit transitions as well as instrument turn on.

Starting with this release, NALT and AMR GDR products will continue to be routinely released with a latency of < 90 days from the end of each repeat cycle.

Users are advised of the following known limitations in the dataset:

  • The adaptive retracker has not yet been calibrated, so the adaptive retracker variables should be used with caution.

Users are advised of the following upcoming changes in the datasets:

  • In the coming weeks, the processing baseline of the SWOT L2 Nadir altimeter products will evolve to use the same MSS (CNES_CLS_2022) and the same MDT (CNES_CLS_2022) as the SWOT KaRIn L2_LR_SSH products.

Users are also advised of the following differences between OGDR, IGDR and GDR:

  • The OGDR is a non-validated product that is available with a typical latency of < 7 hours.

  • The IGDR is a partially validated product that is available with a typical latency of < 2 days.

  • The GDR is a validated product that will become available with a typical latency of < 90 days after the start of release.

See SWOT Level 2 Nadir Altimeter and Advanced Microwave Radiometer Data Product Specifications (Provenance of auxiliary data in OGDR, IGDR, and GDR products and Altimeter retracker outputs in OGDR, IGDR, and GDR)

The NALT and AMR data products in this release are accessible at both NASA’s PO.DAAC and CNES AVISO distribution centers. Information on accessing these data is provided below.


The SWOT Nadir Altimeter and Radiometer (O/I)-GDR products can be accessed on the AVISO+ web portal and through a new platform of the AVISO+ CNES Data Center's long-term archive catalog, accessible directly using AVISO+ credentials. Further information on SWOT data access can be found via the dedicated webpage on AVISO+:

The GDR products in this release are listed below along with the corresponding Digital Object Identifier (DOI) landing pages:

Poseidon-3C Nadir Altimeter

Advanced Microwave Radiometer


The datasets in this release are listed below with links to the corresponding dataset landing pages on the PO.DAAC web portal (

Poseidon-3C Nadir Altimeter

Advanced Microwave Radiometer

Command-line Subscriber example

$ podaac-data-subscriber -c SWOT_L2_NALT_GDR_2.0 -d ./data/SWOT_L2_NALT_GDR_2.0 --start-date 2023-01-15T00:00:00Z

$ podaac-data-subscriber -c SWOT_L2_RAD_GDR_2.0 -d ./data/SWOT_L2_RAD_GDR_2.0 --start-date 2023-01-15T00:00:00Z

Resources for users of SWOT datasets distributed by the PO.DAAC


Comments/Questions? Please contact or visit the PO.DAAC on Earthdata Forum.