NASA, Argentina launch oceanography satellite

Editor's note...
  • Posted at 10:57 AM EDT, 06/10/11: NASA, Argentina launch oceanography satellite
  • Updated at 11:20 AM EDT, 06/10/11: Second upper stage burn; satellite separation
CBS News

A slender Delta 2 rocket boosted the Aquarius/SAC-D oceanography satellite into space Friday, kicking off a long-awaited $287 million mission to measure the salinity of the world's oceans, a key factor in ocean circulation, the water cycle and climate change.

The United Launch Alliance Delta 2 blasted off from Space Launch Complex 2W at Vandenberg Air Force Base, Calif., at 10:20:13 a.m. EDT (GMT-4). Equipped with three solid-fuel strap-on boosters, the rocket quickly climbed away atop a churning trail of exhaust, knifing into a low deck of clouds and disappearing from view.

A United Launch Alliance Delta 2 rocket climbs away from Vandenberg Air Force Base, Calif., on a mission to boost the Aquarius/SAC-D oceanography satellite into space. (Credit: William G. Hartenstein/United Launch Alliance)
The strap-on boosters burned out just over a minute into flight, falling away as planned a half minute later, and the first stage shut down on schedule four minutes and 24 seconds after liftoff. The Delta 2's second stage then boosted the spacecraft into a preliminary orbit with a high point of around 416 miles and a low point of about 98 miles. A 12-second "burn" 52 minutes after launch was designed to put the satellite into a circular 408-mile-high orbit tilted 98 degrees to the equator.

A few moments later, a "rocket cam" on the second stage showed the Aquarius/SAC-D satellite as it was released from the second stage, completing the launch phase of the mission.

"Good spacecraft separation, Aquarius is now flying on its own!" said launch commentator Steve Agid.

Completing a trip around the planet every 98 minutes, Aquarius/SAC-D will map the world's oceans every seven days, charting changes in salinity as small as one-eighth of a teaspoon per gallon of sea water. The satellite is a joint venture between NASA and Argentina's space agency, the Comision Nacional de Actividades Espaciales, or CONAE. Brazil, Canada, France and Italy also are participating in the mission.

The solar-powered 3,000-pound satellite's primary instrument -- Aquarius -- was provided by NASA's Jet Propulsion Laboratory. Seven other instruments are on board to collect a wide range of environmental data, including two that will monitor rain, sea ice, wind speed and surface temperature to complement the Aquarius measurements of dissolved salt at the ocean's surface.

"Measuring ocean surface salinity from space is NASA's latest technology achievement and it's really going to be a great leap forward for the science of oceanography," Eric Lindstrom, Aquarius program scientist at NASA headquarters, told reporters during a pre-launch briefing. "For many of you, salinity is a rather obscure quantity, but I must tell you it's of critical importance in the ocean circulation, in the climate system and in diagnosing the flow of fresh water through our Earth system.

"Salinity is the amount of salt dissolved in seawater and you might be surprised to know it varies through the ocean. ... It's difficult to measure from a ship. We've collected probably a few million measurements over the last hundred years. It's measured in grams of salt in kilograms of seawater. It's typical range is from 32 parts per thousand to 38 parts per thousand. These are small numbers, small differences, but they make enormous difference in the circulation and climate."

While other satellites actively measure ocean temperatures, surface winds and a variety of other factors, "a key missing piece that is really in demand by the ocean science community is salinity," Lindstrom said. "Together with surface temperature, salinity determines the density of the surface water of the ocean. Density variations and wind drive the ocean circulation."

"So this is why we want to get this missing piece," he said. "Particularly, the deep waters of the ocean get their properties at the sea surface in winter, so their temperature and salinity are set for their lifetime, they get dense and sink to the bottom of the ocean and fill up the ocean basins."

Aquarius/SAC-D also will help scientists develop a more complete understanding of the water cycle -- evaporation from the ocean, the formation of clouds, rain, ice and runoff back to the sea. Over the past 50 years, data indicate regions of high salinity are getting saltier.

"Is this an indication we're having an acceleration of the planet's water cycle? The salty places in the subtropical (areas) are having more evaporation, the rain belts are having more precipitation and the ocean is giving us this signal," Lindstrom said. "This is an indicator but there could be other explanations for this. It could be the ocean circulation is changing, it could be ocean mixing is changing.

"What we really need to do as oceanographers is dig into this more deeply and Aquarius will help us illuminate these processes. It's a diagnostic for the water cycle but it can also help us tell about ocean circulation and mixing."