Located on the Canary Island of La Palma, the Swedish 1-meter Solar Telescope (SST) is the world’s leading facility for high resolution observations of the Sun. It is operated by the Institute for Solar Physics(ISF), which is part of Stockholm University’s department for Astrophysics. Research at the institute primarily aims to gain knowledge about the outer layer of the solar atmosphere, which is dominated by magnetic fields.
The mystery of the sun is explored using observational data registered with the Swedish Solar Telescope. The telescope system looks at 60 x 60 arc-seconds of the Sun, which equals 43,320 x 43,320 km on the solar surface. This is an area that is more than three times bigger than the Earth’s surface but represents only 0.03% of the Sun’s surface.
The telescope uses adaptive optics to reduce the effects of atmospheric distortion. Atmospheric distortion is caused by the Earth’s atmosphere, which bends the light in random directions. It is the reason why stars seem to twinkle and why the Sun seems rippled at sunset. Without adaptive optics, the Swedish Solar Telescope would generate blurry images.
The Concept of Adaptive Optics
The adaptive optics system within the Swedish Solar Telescope, which was funded by the Swedish Research Council, consists of a Shack-Hartmann wavefront sensor and a deformable mirror. The Shack-Hartmann wavefront sensor is a glass plate with many lenslets etched on it, which subdivide the pupil of the telescope in 85 segments. Each segment delivers an individual image of the Sun. When the atmosphere disturbs the image, it causes the image to shift, and this shift is different for each segment. The shifts are measured and translated into commands to the deformable mirror, so that it takes a shape that compensates for the distortions.
