The launch is the first in a series of giant balloons which NASA has organized to transport bulky payloads — such as astronomical telescopes — used in astrophysical experiments and research on cosmic radiation.
The westward flight from Esrange to Alaska will test NASA's new long-lasting balloon vehicle and carries a 5,940-pound telescope at an altitude of 25 miles for six to nine days.
"Never before has such a huge balloon been launched from Europe with such a heavy instrument," Esrange spokeswoman Johanna Bergstrom-Roos said.
Mark Devlin, a professor at the University of Pennsylvania who is leading the studies, said the telescope "will address some of the most important cosmological and galactic questions regarding the formation and evolution of stars, galaxies and clusters."
The balloon is 396 feet high and 462 feet in diameter. It is made of advanced materials and uses a pumpkin-shaped design to achieve flights up to 100 days. It holds up to 1.3 million cubic yards of helium.
The flights are being conducted by NASA and the National Scientific Balloon Facility, based in Palestine, Texas, in cooperation with the Swedish Space Corp.
About 450 scientific balloons have been launched since flights started in 1974 from Esrange, about 770 miles north of the capital, Stockholm.