Nasa ocean-watch satellite ready for June launch

The US space agency said it is preparing to launch a satellite to observe levels of salt on the surface of the world’s oceans and how changes in salinity may be linked to future climate.

The June 9 launch of Aquarius/SAC-D comes three months after Nasa lost Glory, a $424 million earth-observing satellite that failed to separate properly from its rocket launcher and plunged into the ocean.

The orbiting science instrument will aim to map the entire open ocean every seven days from its position 657 kilometres above earth, producing monthly estimates that show how salt levels change over time and location.

“There are vast tracts of the ocean where salinity has never been collected, ever,” said Eric Lindstrom, Aquarius programme scientist at Nasa, describing the high level of precision expected from the mission.

“We are going to be sampling the whole planet in one week,” he said.

While a European satellite was launched in 2009 to measure soil moisture and ocean salinity, the Aquarius/SAC-D is a global collaboration – with partner Argentina as well as France, Brazil, Canada and Italy – that will add to scientists’ knowledge of the oceans in novel ways.

“Aquarius will map global variations in salinity in unprecedented detail, leading to new discoveries that will improve our ability to predict future climate,” said principal investigator Gary Lagerloef of the Earth and Space Research in Seattle, Washington.

Scientists from the European Space Agency who launched the Soil Moisture and Ocean Salinity mission have been working in parallel and sometimes in partnership with Nasa and Argentina’s space agency, Comision Nacional de Actividades Espaciales as the two separate missions took shape, he said.

SMOS is a dual-purpose mission whose main focus is soil moisture, while Aquarius is aimed primarily at measuring ocean salinity, which plays a key role in exchanges of water and heat in the atmosphere.

“It has been a strong cooperative effort,” Dr Lagerloef said. “Once we have both of these missions in orbit, we will compare results, we will intercalibrate them,” he said.

“We will do a lot of things cooperatively to provide the best information about ocean surface salinity to the scientific community that we possibly can.”

The satellite observatory is also to carry seven additional instruments to “collect environmental data for a wide range of applications, including studies of natural hazards, air quality, land processes and epidemiology”, Nasa said.