Global sea level, as it inches ever higher, has a new eye keeping watch on it from orbit.

On 20 June, the US and French space agencies launched the next-generation ocean topography satellite, the Ocean Surface Topography Mission, or Jason-2. The satellite will continue to monitor sea-surface height, a continuous series of measurements that began with the present Jason-1 mission.

Jason-2 is a joint venture of two US agencies (NASA and the National Oceanic and Atmospheric Administration), France's space agency (CNES), and the European satellite agency EUMETSAT.

Jason-1 is still operating; Jason-2 will orbit beneath it during its commissioning phase.