The milestone was reached in collaboration with National Aeronautics and Space Administration, NSF said Friday in a release.

Scientists from the United States, Japan, South Korea, France and other countries are using the long-duration sub-orbital flights to investigate the nature of ultra-high-energy cosmic rays and searching for anti-matter as air currents that circle Antarctica carry the balloons and their instruments at the edge of space, NSF said.

The report said unique atmospheric circulation over Antarctica during the Southern Hemisphere summer allows scientists to launch balloons from a site near McMurdo Station and recover them from nearly the same spot weeks later, after the balloons have circled the continent.

Antarctic flights are of a long duration because of the polar vortex and because there is very little atmospheric or temperature change. Constant daylight in Antarctica means no day-to-night temperature fluctuations, which helps the balloon stay at a nearly constant altitude for a longer time.

The three balloons will ride the stratospheric winds in the polar vortex above the Antarctic continent for up to six weeks.