Jason-2 Nadir Altimeter Geophysical Data Records

The Ocean Surface Topography Mission (OSTM)/Jason‑2 was a satellite altimetry mission that operated for more than 11 years, from 2008 to 2019. It was a joint endeavour carried out by NASA and CNES.

OSTM/Jason‑2 measured a suite of geophysical parameters, including significant wave height (SWH), radar backscatter coefficient (σ⁰), wet tropospheric path delay, and ionospheric delay. These observations were processed to retrieve sea‑surface height (SSH) and sea‑level anomalies (SLA). The mission followed a repeat cycle of roughly 10 days, comprising 254 ground tracks per cycle.

The Jason‑2 Geophysical Data Records (GDRs) are Level‑2 products that were distributed with different latencies:

• Operational GDR (OGDR): delivered approximately 3 hours after acquisition (near‑real‑time data for operational use).
• Interim GDR (IGDR): delivered approximately 2.5 days after acquisition (early‑release data for research and monitoring).
• Standard GDR (GDR): delivered approximately 2 months after acquisition (fully validated, higher‑quality data).
• Reprocessed GDRs: released periodically (typically every few years) with improved processing algorithms and updated auxiliary data.

The GDRs are distributed in three file types, each offering a different level of detail:

• GPR: Reduced product (1 Hz sampling, a subset of the full dataset).
• GPN: Normal product (both 1 Hz records and 20 Hz high‑rate measurements).
• GPS: Sensor product (full radar‑echo waveforms, intended for expert users; not available for the OGDR).

In 2025 the GDR‑F (“F” standard) was introduced for Jason‑2, bringing a substantial improvement in both the availability and the accuracy of the GDR products.