This paper describes the wave-front correction system developed for the Sunrise balloon telescope, and provides information about its in-flight performance. For the correction of low-order aberrations, a Correlating Wave-Front Sensor (CWS) was used. It consisted of a six-element Shack-Hartmann wave-front sensor (WFS), a fast tip-tilt mirror for the compensation of image motion, and an active telescope secondary mirror for focus correction. The CWS delivered a stabilized image with a precision of 0.04 arcsec (rms), whenever the coarse pointing was better than 90 arcsec peak-to-peak. The automatic focus adjustment maintained a focus stability of 0.01 waves in the focal plane of the CWS. During the 5.5 day flight, good image quality and stability was achieved during 33 hours, containing 45 sequences that lasted between 10 and 45 minutes.
@article{arxiv.1009.3196,
title = {The Wave-Front Correction System for the Sunrise Balloon-Borne Solar Observatory},
author = {T. Berkefeld and W. Schmidt and D. Soltau and A. Bell and H. P. Doerr and B. Feger and R. Friedlein and K. Gerber and F. Heidecke and T. Kentischer and O. v. d. Lühe and M. Sigwarth and E. Wälde and P. Barthol and W. Deutsch and A. Gandorfer and D. Germerott and B. Grauf and R. Meller and A. Alvarez-Herrero and M. Knölker and V. Martinez Pillet and S. K. Solanki and A. M. Title},
journal= {arXiv preprint arXiv:1009.3196},
year = {2015}
}