The Swarm satellites have deployed their four-meter-long booms and begun activating their science instruments, ESA officials said today.

The booms were folded up against the bodies of the three Swarm satellites when they launched Friday aboard a Russian Rockot booster.

With the booms extended, the identical satellites each measure about 30 feet long.

The booms are essential to Swarm's mission of measuring the Earth's global magnetic field. Two magnetometers are mounted on each satellite's boom, which give the sensors enough distance from the satellite's core structure to ensure they obtain pristine measurements.

Electrical and metallic components in the spacecraft's main body could disturb the magnetic field measurements, according to scientists.

Swarm's GPS tracking system, star trackers and vector field magnetometer have already been activated following launch.

The Swarm mission is designed to study the magnetic field and distinguish its sources deep inside the Earth's interior, in rocks inside Earth's crust, from ocean circulation, and from interactions between the magnetic field and charged particles streaming away from the sun.

Scientists say Swarm's data will help fine-tune models of the magnetic field and could reveal how the field changes over time.

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.

Read our full story.

ESA confirms signals from the third Swarm satellite have been acquired from Svalbard.

Spacecraft separation! The three Swarm satellites have deployed from the Breeze KM upper stage, and two of the spacecraft have established radio contact with a ground station in Sweden.

The third Swarm satellite should contact a ground station in Svalbard in a few minutes.

According to ESA, the Breeze KM restart has been completed. Deployment of the Swarm satellites is expected at 1333:47 GMT (8:33:47 a.m. EST) from a custom-built adapter connecting the three spacecraft to the rocket's upper stage.

Coming up on a short 16-second restart of the Breeze KM upper stage engine to circularize its orbit at an altitude of about 490 kilometers, or 304 miles.

ESA is pausing their coverage for approximately one hour while the Breeze KM upper stage is in a quiet coast period.

ESA reports the Breeze KM and the three Swarm satellites have reached orbit. The upper stage is now starting a 61-minute coast phase before re-igniting its engine at 1318 GMT (8:18 a.m. EST) for a brief 16-second burn.

The Breeze KM burn should last another three minutes to put the Swarm satellites into an initial parking orbit. The rocket is aiming for a temporary orbit with a perigee, or low point, of 153 kilometers and an apogee, or high point, of 476 kilometers.

The Breeze KM burn should last another three minutes to put the Swarm satellites into an initial parking orbit. The rocket is aiming for a temporary orbit with a perigee, or low point, of 153 kilometers and an apogee, or high point, of 476 kilometers.

The Breeze KM engine has started its first burn, according to ESA.

ESA says the Rockot's second stage has shut down and separated. In a few moments, the Breeze KM engine will ignite for the first of two burns to put Swarm into orbit.

The Rockot's 2.6-meter payload fairing has separated, falling away in two clamshell-like halves as the launched passes an altitude of 77 miles (125 km) and a velocity of 8,000 mph (2.6 km per second).

The Rockot is flying north from Plesetsk toward polar orbit.

The Rockot's first stage has jettisoned after consuming its supply of hydrazine and nitrogen tetroxide propellants. The second stage of the modified SS-19 missile is now firing.

Coming up on fairing jettison.

LIFTOFF of the Rockot with Europe's Swarm mission, launching three satellites to map the protective bubble around our planet.

T-minus 2 minutes. The clocks are ticking down to 1202:15 GMT (7:02:15 a.m. EST), the moment when the Rockot's navigation system is initialized for flight.

Ignition of the first stage engines and liftoff comes 14 seconds later.

T-minus 5 minutes. The mobile gantry at the launch pad is in the launch position, revealing the 95-foot-tall Rockot vehicle.

Today's launch will mark the:

• 18th Rockot/Breeze KM launch since 2000
• 3rd Rockot/Breeze KM launch of 2013
• 10th launch of a Breeze upper stage in 2013
• 5th launch from Plesetsk Cosmodrome in 2013
• 4th ESA Earth Explorer mission to be launched
• 4th Rockot launch for ESA
• 62nd, 63rd and 64th ESA satellites

T-minus 10 minutes. The Rockot launcher is running on an automatic countdown sequence. In the final 10 minutes, the service tower at the Plesetsk launch pad will retract to its launch position.

T-minus 15 minutes. The status board at the European Space Operations Center in Germany is "green" for launch of Swarm.

Swarm is the fourth of ESA's Earth Explorer missions dedicated to a facet of the Earth system.

It follows three Earth Explorers launched beginning in 2009:

• The Gravity field and steady-state Ocean Circulation Explorer (GOCE) launched March 17, 2009, and collected high-resolution measurements of Earth's gravity field. Using accelerometers on-board the satellite, GOCE mapped the lumpy variations in Earth's gravity and scientists used the mission's data to create a geoid, or a model of Earth's gravity field without the influence of ocean circulation.
  
  
• The Soil Moisture and Ocean Salinity (SMOS) launched Nov. 2, 2009, with an L-band antenna array to measure moisture trapped in soils and salt concentrations in the world's oceans. The data is helping scientists understand Earth's water cycle.
  
  
• CryoSat launched April 8, 2010, to track changes in the thickness of land and sea ice. The satellite's radar altimeter instrument constantly monitors polar ice movements, and the mission's data helps researchers understand Earth's climate.

More Earth Explorers are queued up for launch in the next few years.

Everything is still "go" for an on-time launch in less than one hour.

"Launch is always a difficult phase in the life of a satellite," said ESA director general Jean-Jacques Dordain in remarks at the European Space Operations Center in Germany. "It's a few minutes of stress to move from the ground to orbit. A launch is never routine."

A poll of Swarm ground controllers the European Space Operations Center in Darmstadt, Germany, one hour before launch will assess their readiness to enter the terminal countdown.

The control team will verify the three 1,040-pound Swarm satellites are in launch mode 15 minutes before liftoff.

Clocks are actually countdown down to 1202:15 GMT (7:02:15 a.m. EST), when the Rockot mission officially begins with the command to initialize the launch vehicle's guidance system.

Liftoff comes 14 seconds later at 1202:29 GMT (7:02:29 a.m. EST).

The 95-foot-tall Rockot, a converted SS-19 ballistic missile, will race into the sky and reach 35,000 feet - cruising altitude for a jetliner - in just 36 seconds.

The liquid-fueled first stage will shut down and jettison about two minutes after liftoff, giving way to the Rockot's second stage for a three-minute burn. The launcher's 8.5-foot (2.6-meter) diameter payload fairing will release in two halves at T+plus 3 minutes, 4 seconds, at an altitude of 77 miles (125 km) and a velocity of more than 8,000 mph (2.6 km/s).

The Rockot second stage will switch off about five minutes after liftoff, leaving the Breeze KM upper stage to take over for a pair of maneuvers to put the Swarm satellites into the targeted 304-mile-high (490-kilometer) orbit.

The burns will be separated by a one-hour cruise phase.

Separation of the Swarm satellites will occur simultaneously at 1333:47 GMT (8:33:47 a.m. EST), followed moments later by acquisition of signals from the satellites through Swedish and Norwegian ground stations.

The European Space Agency is reporting no problems in the countdown at the Plesetsk Cosmodrome. Liftoff the Rockot launch vehicle with Swarm remains set for 1202:29 GMT (7:02:29 a.m. EST).

Swarm's tracking stations in Antarctica, Sweden and the Norwegian island of Svalbard are all reported to be up and ready to support the launch.

Moments after deploying from the Rockot's Breeze KM upper stage, the Swarm satellites will radio ground stations in Svalbard and Kiruna, Sweden.

Upper level winds are reported to be acceptable for launch over the Plesetsk Cosmodrome, which is located in far northern Russia about 500 miles north of Moscow.

Live video coverage from ESA will begin on this page at 1045 GMT (5:45 a.m. EST).

Three identical European-built satellites are packed aboard a Russian rocket for launch Friday on a $280 million mission to map the Earth's magnetic field, an invisible bubble around the planet serves as a shield protecting life from solar and cosmic radiation.

Read our full story.

Russian rocket technicians loaded storable propellants into a Rockot launch vehicle Thursday, one day before the modified missile is set to lift off with a trio of European magnetic field research satellites.

The hydrazine and nitrogen tetroxide propellants power the Rockot's two core stages, plus a Breeze KM upper stage designed to inject the Swarm satellites into a 304-mile-high orbit at an inclination of 87.55 degrees.

The Rockot is a converted SS-19 missile from Russia's Strategic Rocket Forces.

The 95-foot-tall Rockot is set for launch at 1202:29 GMT (7:02:29 a.m. EST) Friday, or 4:02:29 p.m. local time at the Plesetsk Cosmodrome, a military base in far northern Russia's Arkhangelsk region about 500 miles north of Moscow.

Fully loaded with propellant, the Rockot weighs about 107 metric tons. Its four first stage engines generate 420,000 pounds of thrust to propel the rocket out of its container, which is a relic of the launcher's days as a nuclear missile on standby.

The Rockot will fly on a northerly trajectory from Plesestsk before deploying the Breeze KM upper stage for a pair of burns to put the Swarm satellites into the targeted circular orbit.

The Swarm spacecraft, each weighing about 1,040 pounds, will separate from the Breeze KM upper stage at 1333 GMT (8:33 a.m. EST), followed a few minutes later by the acquisition of signals from the satellites by ground stations in Sweden and Norway.

See the launch timeline for more details on the Swarm satellites' ride to orbit.

Going into the Nov. 22 launch of the European Space Agency's $300 million Swarm mission, which promises to collect exquisite data on Earth's magnetic field, European officials say they are satisfied with technical and programmatic fixes introduced by Russian authorities after a series of failures by variants of the Rockot's Breeze upper stage.

Read our full story.