Upgrades to the AO system of the 1.5m GREGOR solar telescope

We present improvements to the telescope and the Adaptive Optics (AO) upgrades that will be installed in 2018 to the 1.5m GREGOR solar telescope. An exchange of the telescope's secondary mirror has improved the contrast in the AO wavefront sensor (WFS). The repair of the telescope building's faulty facade plates will result in better dome/building seeing. The daytime (solar) wavefront sensor camera will be replaced by a high full well capacity model, enabling the AO to lock on granulation and faculae close to the solar limb during bad seeing conditions. A 2x2 guide region ground layer AO (GLAO) mode will provide a 10 " FoV with a much flatter PSF as compared to conventional AO. A change of the night-time wavefront sensor camera will result in a larger WFS FoV, improving the AO tracking of the large solar system planets like Jupiter and Saturn. A new AO mode of operation will allow the tracking of of solar prominences using a narrow-band H-alpha filter.