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Earth-watching satellite launched on watery mission
BY STEPHEN CLARK
SPACEFLIGHT NOW

Posted: November 2, 2009


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A modified Russian ballistic missile successfully launched a $464 million European science satellite Monday to investigate Earth's water cycle by measuring moisture levels in soil and salt concentrations in the world's oceans.

 
The Rockot launcher lifts off with SMOS. Credit: Stephane Corjava/ESA
 
"I'm really happy and relieved," said Achim Hahne, project manager for the Soil Moisture and Ocean Salinity satellite.

The SMOS satellite will spend the next three years creating the best maps of variations of moisture and salt in land areas and the open ocean. This data will help weather forecasters, climatologists, and water resource managers better predict changes in the water cycle.

"SMOS is known as ESA's water mission," said Mark Drinkwater, head of the European Space Agency's mission science division. "It's going to help us understand the complexities of the water cycle on Earth.

Jean-Jacques Dordain, ESA director general, praised the agency's role in space research focused on planet Earth.

"ESA is certainly the space agency of the world making the best efforts for Earth science and climate (research) and this is a new contribution to the understanding of climate," Dordain said.

SMOS and another satellite, called Proba 2, rode into space on the power of a retired ballistic missile taken from the arsenal of the Russian military.

The Rockot launcher flickered to life and roared off its launch pad at Plesetsk Cosmodrome at 0150 GMT Monday (8:50 p.m. EST Sunday), disappearing into fog and low clouds in the predawn hours in northern Russia.

The 95-foot-tall rocket pitched northward from Plesetsk, flying over the Barents Sea as it jettisoned its first stage, payload fairing and second stage within five minutes of liftoff.

The Rockot passed out of communications range with ground stations moments later, leaving ground controllers in the blind until the vehicle appeared again over the Hartebeesthoek communications site in South Africa.

By that point, the 1,451-pound SMOS satellite was separated from the Rockot's Breeze KM upper stage and executing programmed commands to deploy the spacecraft's two solar panels.

"Currently, we are analyzing the telemetry we have received, but we can say the satellite is in good health and the solar panels have been deployed," said Francois Bermudo, SMOS project manager at the French space agency, CNES.

SMOS was planned to be released in an orbit ranging in altitude from 465 miles to 476 miles, with an inclination of 98.4 degrees. Spacecraft separation occurred at about 0300 GMT Monday (10 p.m. EST Sunday).

The Breeze upper stage coasted through space for another circuit of Earth before the $27 million Proba 2 secondary payload was cast free of the rocket.

The 287-pound miniature satellite will demonstrate 17 new space technologies and carries four experiments to study the sun's impact on space weather during its two-year mission. Proba 2 carries test components that could be used on future missions, including the BepiColombo Mercury probe and the Solar Orbiter spacecraft.

"With Proba 2, we are preparing for missions 10 years from now," Dordain said.

SMOS will unfurl three prongs of its Y-shaped antenna Tuesday before the instrument is activated for testing over the next few weeks.

The L-band MIRAS instrument, resembling the rotors of a helicopter, is a first-of-a-kind payload comprising 69 individual antennas stringed together in an inferometer-like array to maximize the sensor's sensitivity.


One arm of the MIRAS instrument is seen in pre-launch tests, showing a portion of the 69 individual antennas. Credit: ESA
 
Each of the small antennas will measure faint radio signals emitted by Earth and an on-board processor will bind the data together before sending the packets back to scientists on the ground.

The MIRAS radiometer was built by EADS CASA in Spain.

Development of the ground-breaking technologies required for such an instrument began in 1992. The engineering design was finally mature enough for the SMOS mission to be formally proposed in 1998.

"MIRAS is really a radio telescope looking down instead of up," said Manuel Martin-Neira, payload engineer on the SMOS mission. "But to gather an image of useful resolution would require a classical antenna of at least eight meters (26 feet) across, far too bulky to fly on the launcher and satellite platform available."

"When we think about it's sensitivity, we can think about measuring on the order of one teaspoon of fresh water in the upper layer of soil," Drinkwater said.

Soil moisture is a key factor in determining humidity in the atmosphere and the formation of precipitation.

"Water is the main driver for the exchanges between the atmosphere and the soil," said Yann Kerr, SMOS lead investigator at CESBIO, a French space research agency. "Monitoring these changes help us have better weather forecasts and better monitor climate changes."

Officials hope data from SMOS will be fed into numerical weather prediction models to aid meteorologists in making more accurate forecasts.

"Being able to measure accurately the water available in the skin of the Earth helps us have a better understanding of the future weather," Kerr said.

Soil moisture is also important for researchers studying plant growth and vegetation distributions.

"With SMOS, it will be the first time that we have measured soil moisture with an accuracy of 4 percent, which will allow us to get 10 to 11 classes of soil wetness," said Matthias Drusch, SMOS mission scientist.

SMOS will create maps of soil moisture in 30-mile-wide blocks and maps of ocean salinity in boxes 120 miles across.

Ocean salinity data from SMOS will tell scientists how the atmosphere and oceans interact.


Artist's concept of the SMOS satellite with deployed solar arrays and instrument. Credit: ESA
 
Scientists will also gain new insights on ocean circulation, one of the most important drivers of world climate. Like conveyor belts, circulation patterns transport warm water to high latitudes and cool water to low latitudes, moderating the planet's climate.

"It helps to maintain a balance of temperature across the globe," Drinkwater said.

The temperature and saltiness of the water help determine ocean circulation patterns.

"That's why SMOS was really crafted as a mission to get a look at how the salinity varies globally from one region in the ocean to another, since it's the variations that really drive the circulation," Drinkwater said.

SMOS data will be used to make weekly, seasonal and annual maps of salinity and moisture levels.

"The ability of SMOS is really helped by the fact that we can map the whole globe every few days," Drinkwater said. "We accumulate data over intervals of two weeks to a month, and we can make a global picture of the salinity in grid cells around the globe on those intervals of time."

In its ocean salinity investigations, the two-dimensional SMOS radiometer can detect one-tenth of a gram of salt in a liter of water.

All of these measurements occur as SMOS orbits nearly 500 miles above Earth.

"That's a mind-boggling thought," Drinkwater said.

SMOS will be the first satellite capable of gathering global observations of soil moisture and ocean salinity, building on previous point measurements made by aircraft, ships and buoys.

NASA is planning two satellites, Aquarius and SMAP, for launch in 2010 and 2014 to make further measurements of salinity and soil moisture, respectively.

The SMOS mission's price tag of about 315 million euros, or $464 million, was divided between ESA and CNES.

CNES will conduct the day-to-day operations of the satellite, while ESA will be responsible for management of the mission and the ground segment.

Normal science activities should begin about six months after launch, starting two-and-a-half years of activities to map the distribution of moisture in soil and salt in ocean water.

But SMOS could last much longer.

SMOS is the second of ESA's Earth Explorer missions, which were conceived to follow up on observations of the agency's flagship Envisat satellite launched in 2002.

The gravity-mapping GOCE spacecraft launched on another Rockot vehicle in March. The CryoSat 2 mission, a replacement for a satellite lost in 2005, is due for launch on a Dnepr rocket in February to probe the polar ice caps.

"There are many aspects of Earth we don't know about to the extent necessary. For example, the gravity field, soil moisture, ocean salinity, to give only three examples which we are going to measure," said Volker Liebig, director of ESA's Earth observation programs.

"I like to see the three missions as very powerful triplets to help address the key climate questions that we have today," Drinkwater said.

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