The European Space Agency (ESA) orbited its Swarm Earth-observation mission atop a Russian Rockot launcher Nov. 22, sending a trio of research satellites 500 km (300 mi.) above the planet’s surface to study the magnetic field that protects it from cosmic radiation and charged particles in the solar wind.

Liftoff occurred at 7:02 a.m. EST from the Plesetsk Cosmodrome in northern Russia. At 100 min. after launch, ESA confirmed the three identical spacecraft were healthy in orbit and sending telemetry to the European Satellite Operations Center (ESOC) here via the agency’s ground stations in Kiruna, Sweden, and Svalbard, Norway.

Led by prime contractor Astrium Satellites of Germany, the Swarm mission comprises two spacecraft flying side-by-side at an initial altitude of 460 km to measure the east-west gradient of the Earth’s magnetic field, accompanied by a third spacecraft flying initially at a higher altitude of 530 km.

Each satellite weighed 473 kg (1,040 lb.) at launch and measures 1.5 meters (5 ft.) wide, 0.85 meters high and 9.1 meters long, including a 4-meter deployable boom. Instruments aboard the satellites include a vector field magnetometer, absolute scalar magnetometer, electric field instrument, accelerometer, GPS receiver, startrackers and a laser retroreflector.

Over a period of four years, the Swarm mission is expected to measure the magnetic field with unprecedented accuracy, aimed at improving scientific understanding of the Earth’s interior and how it interacts with space. The mission is designed to complement ESA’s Cluster constellation, a solar wind-monitoring mission launched in 2000. Cluster has operated well beyond its design life and is expected to continue gathering scientific data through the end of 2014.

ESA approved Swarm in 2004, earmarking €180 million ($240 million in today’s dollars) for the development, construction and launch of its fourth Earth Explorer mission. The four-year development contract initially valued at €86 million was signed with Astrium Satellites in 2005, with launch slated for 2010.

ESA says technical challenges associated with the mission, including the need to keep spacecraft components and the tools used to construct them “magnetically clean” and free of ferromagnetic particles, contributed to a two-year extension of project development.

“A lot of effort went into characterizing all the equipment and how it behaves and the signals it produces at the location of the magnetometers,” says Roger Haagmans, ESA’s Swarm mission project scientist. “After all, you want to measure what the Earth is doing, not what the satellite is doing.”

In April 2010, ESA signed a launch contract with German-Russian joint venture Eurockot Launch Services for simultaneous launch of all three Swarm satellites atop a Rockot vehicle, a converted intercontinental ballistic missile equipped with a Briz KM upper stage. Valued at €27 million, the agreement included development, construction and test of a unique three-satellite dispenser led by Moscow-based Khrunichev, the prime contractor for the Briz KM upper stage.

Since then Swarm has been repeatedly delayed, owing primarily to technical issues associated with the Rockot, which added 16 months to the mission schedule and cost ESA €26 million in storage and other additional fees. As a result, the total cost of Swarm today is €236 million ($316 million) including development, construction, launch, ground infrastructure and operations, says Volker Liebig, director of ESA’s Earth-observation program.

The first Swarm launch delay occurred following a February 2011 mishap that left a Rockot’s satellite payload in a lower-than-intended orbit, says Eurockot CEO York Viertel. After the launch, Russia conducted a lengthy failure analysis that grounded the fleet and pushed Swarm from an early 2012 launch into spring of 2013.

“They did ballistic analysis and identified the critical areas and implemented some corrective actions in the attitude determination system,” Viertel said, adding that Moscow’s investigation was complicated by a lack of telemetry from the balky upper stage.

Then in January, a Rockot launch of three Russian military communications satellites resulted in a similar upper-stage anomaly. Moscow called the mission a success, but in the weeks following, industry sources say the anomaly resulted in the loss at least one of the satellites.

“The technical issue was probably the same, but this time we had telemetry,” Viertel said of Russia’s subsequent investigation. “This improved our understanding of the issue in the attitude control system.”

The latest launch delay, which pushed Swarm’s liftoff from Nov. 14 to Nov. 22, came when Khrunichev opted to replace a gyro in the launcher’s Briz upper stage, according to ESA.

On the bright side, the months of delay gave ESA and Astrium additional time to refine the Swarm mission, and in some cases improve it. A silicon-carbide material used to develop Swarm’s scalar magnetometers was found to be contaminated with feromagnetic particles left over from the instrument’s manufacturing process. The launch delay allowed time for the company to replace them, says Eckard Settelmeyer, director of Earth observation, navigation and space at Astrium Satellites.“We cleaned the process and adapted the manufacturing to rebuild and improve these instruments.”