The U.S. space agency, NASA, has launched two satellites to improve understanding of global climate.

Deployed from a single Delta rocket launched from California on December 7, one satellite peers at the ocean, while the other is to provide an unprecedented view of the little studied, middle region of Earth's atmosphere.

The ocean plays a key role in the world's climate, and a French-U.S. satellite named Jason will observe its movement.

The second satellite, a NASA project named TIMED, will be taking data from the mesosphere, lower thermosphere, and ionosphere.

NASA Earth scientist Ghassem Asrar says that despite their distinct missions, the satellites have the common goal of helping us understand Earth's climate variations.

"On the one hand, TIMED will help us understand the impact of external forces, the variation of the sun and its impact on Earth's atmosphere and climate. Jason will help us understand internal forces, basically changes that are happening in the oceans. The oceans are basically the heat engines of Earth's climate," Mr. Asrar explains.

Mr. Asrar explains that ocean absorbs most of the heat Earth gets from the sun and transports it from the tropics to the poles. Along the way, the heat interacts with the atmosphere to shape global climate.

The French-American Jason satellite will use radar to measure the topography of the oceans once every 10 days to an accuracy of one centimeter. The topographical maps will let scientists determine the circulation of the heat-bearing currents.

Jason will complement an older French-U.S. satellite named Topex-Poseidon that has been tracking ocean currents using a less sharp topographical radar. Until Topex's launch in 1992, oceanographers studied currents from ships, but did not have the global view of a satellite.

The project manager for the American side, Gary Kuntsmann, says together, the new and old spacecraft will double the coverage of the ocean. "The extended data record that Topex and Jason will accumulate allows scientists to determine the long term changes that we expect in the global ocean surface that affects climate and ultimately has a significant affect on society as a whole," he says.

The other satellite launched on the Delta rocket, TIMED, is designed to orbit at 625 kilometers altitude and gaze down at the region of the atmosphere between 60 to 180 kilometers. NASA says the region is greatly influenced by the sun's magnetic field and radiant energy, but is not well studied because it is on the edge of space.

It is too high for balloons, sounding rockets, and aircraft to probe in detail and too low for spacecraft. NASA's manager for the project, Bruce Campbell, says TIMED will provide the first comprehensive picture of temperature, wind, and chemical composition of the region.

"The sun shines down on this area, adds energy to it, causes chemical changes and dynamic changes such as winds and transport. The instruments have been designed to look at the sun for the energy input and to look at the chemistry and dynamics to try to figure out the energy balance that goes through this region," Mr. Campbell explains.

Mr. Campbell says the TIMED satellite takes advantage of recent advances in remote sensing technology that allow it to pick up faint signals given off by the atmosphere several hundred kilometers below it.

Scientists working with TIMED see it as a tool to improve short-term forecasts of middle atmosphere conditions. Ghassem Asrar says the goal is similar for forecasting the ocean's impact on the atmosphere. "Hopefully within the next decade, we will have an ocean observing system very similar to what we have for the short-term weather observations at the moment," he says.

Mr. Asrar says U.S., French, and European space and meteorological organizations are already discussing the successor to the Jason oceanography satellite.