Swarm satellites blast off to explore Earth's magnetic field
BY STEPHEN CLARK
Posted: November 22, 2013
A swarm of three European magnetic field research satellites rocketed into orbit Friday from a wintry launch pad in northern Russia, kicking off a four-year mission to catalog the sources behind Earth's shield against radiation and solar storms.
The Swarm satellites were tucked inside the Rockot's nose cone at liftoff, and the launcher successfully guided the spacecraft into a near-circular orbit about 300 miles above Earth before deploying the payloads 91 minutes into the mission.
Controllers at the European Space Operations Center in Darmstadt, Germany, confirmed all three satellites - nicknamed Alpha, Beta and Charlie - were in the correct orbit and responding to commands.
"The three babies are in good shape," said ESA director general Jean-Jacques Dordain. "A long life to Alpha, Beta and Charlie."
Late Friday and early Saturday, the satellites were expected to extend 13-foot instrument booms. Each satellite's deployable appendage carries two magnetometers provided by institutions in France and Denmark, and the booms ensure the sensors are far enough away avoid magnetic interference from the spacecraft.
Built by EADS Astrium in Germany, the satellites each weighed about 1,042 pounds at the time of launch, including freon propellant for several months of maneuvers to put the craft in the right locations for the mission.
The satellites are carbon copies of each other, and each of the three spacecraft could occupy any position in Swarm's constellation.
In the next three months, two of the Swarm satellites will drop altitude to about 285 miles. The third satellite will raise its orbit to 329 miles, allowing the trio to cross paths in space to obtain three-dimensional measurements of the magnetic field.
"Why do we have two eyes? We - mankind - and animals have two eyes because we want to see three dimensions," said Eigil Friis-Christensen, Swarm lead investigator and director of DTU Space at the Technical University of Denmark. "That is what you can do with two satellites in the pair that is part of the Swarm project. But if you want to also see the fourth dimension, which is time, then you need three satellites."
The higher satellite, in an entirely different kind of orbit, will see how the field changes over longer time scales.
"Swarm is about to fill a gap in our view of the Earth system and in our monitoring of global change issues," said Volker Liebig, ESA's director for Earth observation. "It will help us to better understand the field that protects us from the particles and radiation coming from the sun."
ESA invested $280 million in the Swarm mission, and the French space agency CNES paid for the development of one of the project's magnetometers.
Pier Paolo Emanuelli, ESA's flight operations director at ESOC, said ground controllers issued their first commands to the Swarm satellites a few minutes after they separated from the Rockot's Breeze KM upper stage.
By Sunday, the Swarm's critical launch and early-orbit operations phase should be complete, according to Emanuelli. Three months of orbit adjustments and scientific commissioning are on tap before Swarm is operational, Emanuelli said.
"We will switch on all instruments within the first month, some on the first day, and do a verification and calibration campaign," said Rune Floberghagen, ESA's Swarm mission manager. "If the instruments are fully functional, we will start to distribute data as quickly as possible."
"We would like to squeeze out one full solar cycle because then we can fully characteirze solar cycle's effect on the magnetic field," Floberghagen said.
European scientists say Swarm is uniquely equipped to tease out what processes make up the source of Earth's magnetic field.
"By having three satellites at three different points of the magnetic field, we can see the three-dimensional structures," Liebig said. "We can also distinguish better between the different parts of the magnetic field."
The field behaves like a bar magnet with a north pole and south pole with magnetic field lines stretching into space, creating a bubble known as the magnetosphere. On the day side of Earth, the solar wind compresses the magnetosphere and charged particles stream around the planet and follow field lines into the poles, spawning the colorful auroras.
On the side of Earth facing away from the sun, the magnetosphere is blown out like the tail of a comet.
The primary force behind the magnetic field is the Earth's internal dynamo, where convection produces electric currents that spiral out of Earth, through the atmosphere and thousands of miles into space.
But magnetism from rocks in the Earth's crust and from the circulation of the oceans also contribute to the magnetic field, and solar activity is also an influence in the ionosphere and magnetosphere, the protective bubble around the planet.
"All models that exist today will be improved in resolution, in space and time and quality," Haagmans said.
The magnetic field appears to be weakening, according to researchers, and the magnetic poles have been drifting over the last few decades, leading some experts to suggest Earth is on the verge of a pole reversal.
The magnetic reversal has occurred, on average, about once every 250,000 years. But research shows the last time it happened was 780,000 years ago.
"The last inversion was 780,000 years ago," Liebig said. "We survived it once since Homo erectus was already on the planet. Many scientists believe we are in the middle of another inversion."
The reversal's potential impact on modern humans, especially high-tech electrical grids, navigation and communications, is another question.
"This is a very open question, and this is one of the things we are going to look at with this mission," Haagmans said.
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