Jason-1 will replace the old Topex/Poseidon satellite. Here is what is happening.
In August of 1992, a joint venture between the United States and France sent the TOPEX/POSEIDON satellite into Earth orbit. TOPEX is an acronym that stands for Ocean Topography Experiment. The name TOPEX comes from the US contribution to the project. Poseidon was the Greek God who held power over the oceans. The name Poseidon comes from the French contribution to the project.
TOPEX/POSEIDON measures sea level with amazing accuracy. To find out how something 1,336 km above the planet can measure the rise and fall of the ocean to within a centimeter check out our Satellites page. The T/P has other uses as well. It helps warn meteorologists, the people who study the weather, about El Niño and La Niña and other weather patterns. It is helpful in ship routing, commercial fishing, sailing, hurricane prediction, studying ocean circulation, climate forecasting and many other things you wouldn't even think of.
T/P was only supposed to last a three years, but it was working so well that in 1995 it was given an extension. After 10 years of service, it is being replaced by Jason-1, the best altimeter satellites there is. It will give near-time data with a delay of only 3 hours. That means 3 hours after Jason-1 has measured something, the scientists here on Earth will know just what it saw.
The Jason-1 satellite was named for a hero from Greek mythology. Jason and the Argonauts, the crew of his ship the Argo, went on adventures in search of the Golden Fleece. The satellite was named after Jason because he was a sailor fascinated by the ocean and because he worked with many different kinds of people. Together they went on difficult and dangerous adventures for a good cause just like the two groups, NASA/JPL and CNES, working on Jason-1. The satellite is called Jason-1 because it is hoped to be the first in a 20 year long series of Jason satellite missions.
The Jason-1 satellite mission is totally unrelated to The Jason Project, just in case you were confused.