Aviso: all set for GDRs

Patrick Vincent (Cnes, France)

Joint Verification Team (JVT) meeting at the Jet Propulsion Laboratory (JPL), Pasadena, California. February 24, 1993. Terrible weather. But Cnes Chief Scientist Michel Lefebvre helps us keep our spirits up. He's just learned that he's a grandfather again. Michel does a quick survey of all the children born into the families of engineers and scientists working on Topex/Poseidon.

One day, he tells us, some of these little ones will want to play a few bars from the music of Topex/Poseidon, the overture for a concert of new music from other satellite oceanographic missions.

OK! You can count on all of us Aviso people to hum the Topex/Poseidon melody for a long time yet . . . But first, let's look at what we've already achieved.

Data was distributed gradually during the Topex/Poseidon Verification phase: test CD-Roms, followed by four with version-0 merged Interim Geophysical Data Records (IGDR-Ms), and in less than two months ten merged IGDRs distributed before the JVT meeting.
PIs not only helped validate the first measurements, they also soon had access to data to "map" the ocean. Teams from the GRGS, from the IMG, Ifremer and the University of Delft report in this issue.

Others will follow, I am sure, to show that Topex/Poseidon is taking our knowledge of the ocean a quantum leap forward. The objectives behind Aviso are to:
- inform users,
- distribute data and receive the PIs' expert comments,
- receive users' feedback and act on it.

Aviso has been made possible by good coordination between the data management experts and the scientists.
The distribution of version-1 CD-Roms, a big improvement in the quality of the scientific data, soon provided proof of Aviso's flexibility and reprocessing capabilities. Aviso is not simply a passive distribution and archiving center, but an attentive partner for the scientists.

We've worked hard on product quality: data processing quality but also scientific quality thanks to routine visual checks, statistics and analyses of differences at crossover points. The CLS Space Oceanography Group has played a key role: thanks to the Aviso/Quick-look processing systems it set up for Cnes, the Topex/Poseidon merged products have been validated and several anomalies identified.

The Geophysical Data Record (GDR) stage will start soon.
As several of the presentations at the JVT meeting showed, joint use of the measurements from the two altimeters is now possible and must continue.
The Aviso data on CD-Roms will progress further. Take advantage: if you have any suggestions on how we could improve the quality and contents of the merged products, or ideas for altimetric products that could be useful for oceanography or geophysics, please let us know.

Michel, thank you! Your enthusiasm is contagious: I've got the bug, and I'm not the only one. The Aviso teams will nurture and spread it by continuing to talk with users. Engineers and scientists have been talking for over ten years to make Topex/Poseidon succeed. Let's keep the dialog going: more missions will come . . .