15, 20 and 25 Years of Progress in Radar Altimetry Symposia are scientific events. Conceived just after the Envisat launch by an ESA requirement to organise a Radar Altimetry Workshop (as done for the other Envisat sensors), the first was the "15 Years of Progress in Radar Altimetry" Symposium (15YPRA), March 2006, Venice, Italy, co-chaired by Jérôme Benveniste (ESA) and Yves Ménard (CNES), 15 years after the launch of ERS-1 and TOPEX/Poseidon. Following the success and the eagerness of the participants to have a sequel 5 years later (and not 15 years as initially proposed by the co-chairs in the closing ceremony), the second symposium, 20YPRA, was organised in 2012 in Venice as well, co-chaired by Jérôme Benveniste (ESA) and Rosemary Morrow (LEGOS for CNES).

This scientific Symposium series is traditionally co-organised with CNES to unite these infrequent events with the " incontournable" (unavoidable) annual meeting of the Ocean Surface Topography Science Team (OSTST). Note that the Progress in Radar Altimetry symposium series covers also non-ocean themes: inland water and cryosphere. The logistics of these events are coordinated by ESA.

The outcome of the Symposia includes a "Summary and Recommendations" document. In the past, these documents were milestones and prospective tools gathering Community requirements for the shaping of the future of altimetry.

The web site for 20YPRA is archived at https://altimetry.esa.int/20ypra/ (the original domain name www.altimetry2012.org has been suspended and the ownership is being transferred to ESA and the site will reborn).

The web site for 15YPRA is found at http://earth.esa.int/venice06

Proceedings of the 15YPRA is on CD-Rom and at http://www.esa.int/esapub/conference/toc/tocSP614.pdf
Proceedings of the 20YPRA is on CD-Rom and at http://www.spacebooks-online.com
Summary and recommendations from the “20 Years of Progress in Radar Altimetry” symposium, by Jérôme Benveniste, Rosemary Morrow, Jean-Louis Fellous and Albert Fischer is available at http://www.spacebooks-online.com/product_info.php?cPath=104&products_id=17546

With 25 years of altimetry time-series since the first supply of ERS-1 and TOPEX/Poseidon data products, as a sequel to the 15 and 20 Years of Progress in Radar Altimetry Symposia held in Venice, ESA is organising the "25 Years of Progress in Radar Altimetry" Symposium in collaboration with CNES. As in the past, this a joint event with the annual meeting of the Ocean Surface Topography Science Team (OSTST) and the International Doris Service (IDS) workshop, as well as other potential thematic workshops still to be organised; relevant topics are Sea Level Budget Closure for Climate, Coastal Zone, Space for Hydrology, Operational Oceanography, etc. These events will be held over 6 days, from 24 to 29 of September 2018, in Ponta Delgada, São Miguel Island, Azores Archipelago, Portugal.

We see a great opportunity for gathering the Altimetry Community in the middle of the Atlantic Ocean, which, beyond the symbol of international cooperation, is a fine place to spend a week or more.