Test flight of the solar telescope Sunrise (in New Mexico 2007).
Photo: P. Bathol / MPS
The solar telescope "Sunrise III" successfully launched into space on Thursday night.
The floating telescope will observe the sun from a height of around 35 kilometers for about four or five days.
The unusual thing about it: The solar telescope, with a total weight of almost two tons, was not sent up on board a rocket, but was dangled from a huge helium balloon.
The telescope with a mirror diameter of one meter is the largest solar telescope that has ever left the earth.
Its sensors can image the home star, which is around 152 million kilometers away, with a resolution of 100 kilometers.
The stratospheric flight runs from east to west, the balloon with a diameter of 134 meters is carried by the high-altitude winds.
After a few days, the flying eye lands somewhere in the Canadian wasteland with the help of a parachute.
There it is recovered to possibly fly again later.
From the ground, the high-quality optics would provide little insight, because the earth's atmosphere disturbs the view, especially the UV light is blocked by water vapor and the ozone layer.
During the multi-day stratospheric flight, the Sunrise telescope is therefore far above most of the disturbing atmosphere.
“Since we are flying in summer time and beyond the Arctic Circle, Sunrise III can look at the sun continuously throughout the flight,” says mission leader Sami K. Solanki from the Max Planck Institute for Solar System Research (MPS) in Göttingen.
While ground-based telescopes can only observe the sun during the day, the sun never sets during stratospheric flight.
Because the swaying platform under the balloon is constantly in motion, the telescope automatically aligns itself with the sun again and again.
It is not the first flight of this kind, the Sunrise mission has already set off twice, in 2009 and 2013. The data from the first two flights were productive: more than 100 scientific publications have emerged from them.
What was particularly surprising was how dynamic vortices and tornadoes raged under the sun's surface.
In addition to the MPS in Göttingen, many other institutions are involved in the project, including the US space agency Nasa and institutes from Spain, Sweden and Germany.
The balloon is controlled from the USA by researchers at Johns Hopkins University in Baltimore (Maryland).
The special strength of the dangling celestial eye: In addition to UV radiation, the telescope also registers the temperature, magnetic field and height profile of the observed region on the sun.
Sunrise does not look at the visible surface of the sun, but at the turbulence in the regions hidden underneath.
"Sunrise III can make an important contribution to understanding how the sun manages to heat its outer shell to unbelievable temperatures of more than one million degrees Celsius," says Solanki.
»Answering this question requires a very special view of the sun.«
But flying in a balloon also has disadvantages.
The aircraft has a volume of almost one million cubic meters - more than twice as much as Cologne Cathedral - but together with the telescope it only weighs around six tons.
The feather-light giant is correspondingly sensitive to strong winds.
Not only must there be almost no wind on the ground, but also in the air layers above, up to the cruising altitude of 35 kilometers.
After weeks of waiting, the weather conditions have finally calmed down, and the telescope has been traveling west ever since, with the sun firmly in view.