The SSALTO/DUACS Multimission Altimeter Processing System


The French SSALTO/DUACS multimission altimeter processing system combines data from all altimetric satellites to produce a near-global product of absolute and relative sea surface height. SSALTO stands for Segment Sol multi-missions dALTimetrie, d’orbitographie et de localisation precise; DUACS stands for Data Unification and Altimeter Combination System, or Developing Use of Altimetry for Climate Studies. The data set provides a near-global data set of geostrophic currents (idea for this post is courtesy Lei Wang).

SSALTO/DUACS processes data from all altimeter missions, including the Chinese HY-2A, Saral/AltiKa, Cryosat-2, OSTM/Jason-2, Jason-1, Topex/Poseidon, Envisat, GFO, ERS- 1&2 and even Geosat. From each satellite, SSALTO/DUACS uses the Interim Geophysical Data Record (IGDR), where these are 1-second averages available within 3 days of data collection, from all altimeters. For greater accuracy, the reader should use the GDR, which is a validated record available with a 6-week time lag. Examination of the image shows that the combined product provides data north into Arctic and south to the Antarctic coast. The website for the system and directions on obtaining data are at; the handbook for the data set is at


About Seelye Martin

Seelye Martin received his Ph.D. in engineering mechanics from Johns Hopkins University in 1967 then spent two years as a research associate in the Department of Meteorology at the Massachusetts Institute of Technology. In 1969 he took up a position in the School of Oceanography at the University of Washington where he is now an Emeritus Professor. Beginning in 1987, he taught courses on remote sensing of the oceans. Professor Martin has been involved with passive microwave, visible/infrared and radar ice research since 1979, and has served on a number of NASA and NOAA committees and panels involving remote sensing and high latitude processes. He has made many trips to the Arctic for research on sea ice properties and oceanography. From 2006-2008, he worked at NASA Headquarters as Program Manager for the Cryosphere, where he also served as program scientist for the ICESat-1 and ICESat-2 missions. After leaving Headquarters, from 2009 -2012, he worked in a variety of roles for the NASA high-latitude IceBridge remote sensing aircraft program. For this work, in 2012 he was awarded the NASA Exceptional Public Service Medal.
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