The basic principle of altimetry satellites is to measure the distance between the satellite and the target surface (oceans or continental surface waters) by measuring the round-trip time of a radar pulse.
However, this is not the only measurement taken by the altimeter, and other interesting information can be derived from it : the amplitude and shape of the echoes (or waveforms) also contain information about the characteristics of the target surface (e.g., significant wave heights).
Sea level rise averages 3.6 mm/year ( 11 cm since 1993) globally and reflects large-scale environmental and climatic effects, such as the melting of glaciers and ice caps. There is also evidence that the rate of sea level rise is accelerating. Based on altimetry data, this acceleration is estimated at 1.2 mm per year per decade. In concrete terms, this means that the rate of sea level rise doubled between the decade 1993-2003 (2.1 mm/year) and the decade 2013-2023 (4.4 mm/year).
On November 21, 2020, the first of the Sentinel-6 (Michael Freilich) satellites was launched, a series of satellites dedicated to the continuity of altimetry and climate measurements, taking over from the iconic Topex/Jason series of altimetry satellites (1992-2021).
Five years later, in accordance with the Copernicus program, its successor Sentinel-6B was launched on November 16 at 9:21 p.m. local time from Vandenberg Space Force Base in the United States (https://cnes.fr/actualites/sentinel-6b-un-oeil-oceans-surveillance-climat).
After the calibration and validation phase, which is expected to last 12 months, Sentinel-6B will become the new altimetry reference mission, replacing Sentinel-6A, and will continue its mission in the service of the scientific community and operational applications.
This international scientific community in altimetry has been growing since the 1990s and now has nearly 350 members through the Ocean Surface Topography Science Team, co-chaired by Pascal Bonnefond, a researcher at LTE.
Pascal Bonnefond is also the scientific advisor for CNES projects relating to satellite altimetry missions.
Le laboratoire LTE contribue aussi à l’altimétrie satellitaire en traitant les observations obtenues par les techniques de géodésie spatiale (systèmes de positionnement GNSS et DORIS, télémétrie laser sur les satellites artificiels et sur la Lune et interférométrie radio à très longue base sur les radiosources extragalactiques (VLBI)), en partie dans le cadre du Service de la rotation de la Terre et IERS (International Earth rotation and Reference systems Service) et du centre d’analyse et de données VLBI, composante de l’IVS (International VLBI Service for geodesy and astrometry).
Learn more
An explanatory video about the projectt
Relive the launch of Sentinel-6B
Contact
Pascal Bonnefond, LTE researcher
