The Delta 2 rocket blasted off before 7:30 a.m. PT under cloudy skies. The launch was delayed by a day so that engineers could review issues with the rocket's flight plan.
Several instruments are on board including /*NASA*/'s Aquarius, which will measure the concentration of dissolved salt at the sea surface. The amount of brine in the ocean remains mostly unchanged, but salt levels in the uppermost layer vary around the globe.
NASA is set to produce monthly maps detailing changes in salt levels over three years.
Scientists hope the $400 million mission will help them better predict future climate change and phenomena such as El Nino and La Nina.
Besides Aquarius, seven other instruments will collect environmental data including a camera that will make images of volcanic eruptions, wildfires and nighttime light.
Aquarius joins a European satellite that has been gathering data on both sea salt and soil moisture since 2009. Unlike the European mission, Aquarius will focus only on the ocean.
The Associated Press contributed to this report.