Jason A Spot



Satellite providing global sea surface height observations for climate monitoring and ocean and seasonal forecasting

Jason A Spot
Jason A Spot

The Jason-3 ocean altimetry satellite continues a time series of mean sea level rise measurements dating back to 1992.

Last Updated

16 January 2024

Published on

28 July 2020

The Jason-3 satellite was launched in January 2016  and operates in low Earth orbit at 1336km altitude. Its main instrument is a radar altimeter which provides measurements of sea surface height, wind speed at the ocean surface and significant wave height.

Monitoring global sea level

Jason-3 is the fourth in the series of US/European ocean altimetry satellites (TOPEX/Poseidon, Jason-1, and -2) that, together, have built up a time series of global mean sea level that dates back to 1992.

Variations in sea level in our changing climate (mm per year) can only be monitored on a global scale by ocean altimetry. These measurements are also essential to understand how the ocean stores and redistributes heat, water and carbon in the climate system. 

Global Mean Sea Level as constructed from the data of TOPEX/Poseidon, Jason-1, Jason-2, Jason-3 and Sentinel-6A Michael Freihlich.

Seasonal forecasting and climate monitoring

Jason 3

Seasonal forecasting aims to provide useful information about the climate that can be expected in the coming months. Having a precise knowledge of the ocean state is essential when trying to forecast what the climate will be like six months ahead, thus, altimetry is a source of vital data for seasonal forecasting models.

Changes in the energy balance between the oceans and atmosphere play an important role in the planet's climate change. From the seasonal to the decadal, or even the centennial timeframe, knowledge about the ocean state and its influence on the atmosphere is one of the keys to climate forecasting. Jason-3 aids a better understanding of how oceans and climate interact.

Jason-3 carries five main instruments:

  • The Poseidon-3B radar altimeter is the mission’s main instrument. It measures the distance from the satellite to the ocean surface, wave height and wind speed.
  • The Advanced Microwave Radiometer (AMR) measures atmospheric water vapour. This information is used to correct for the impact of water vapour on the radar signal that the Poseidon-3B altimeter receives. 
  • The DORIS instrument is used to keep a precise track of the Jason-3 satellite’s position in its orbit.
  • The GPSP (Global Positioning System Payload) is also used to establish the satellite’s exact position.
  • The Laser Retroreflector Array (LRA) is an array of mirrors that are used to provide a target to bounce back laser tracking measurements from the ground. This information is used to precisely locate the satellite in its orbit. 

International cooperation

Jason-3 is the result of an international partnership between EUMETSAT, CNES, NOAA, NASA and the European Union, which funds European contributions to Jason-3 operations as part of its Copernicus programme.

EUMETSAT, CNES and NOAA process data from Jason-3, with EUMETSAT being responsible for data services to users of the EUMETSAT and EU Member States, on behalf of the EU Copernicus programme.

This international cooperation has continued with the Jason Continuity of Service programme, which fulfils the Copernicus Sentinel-6 mission. The Sentinel-6 mission will ensure the collection of high-quality sea-level measurement data until at least 2035.