2010, Strassmeier, K.G., Granzer, T., Weber, M., Woche, M., Popow, E., Jrvinen, A., Bartus, J., Bauer, S.-M., Dionies, F., Fechner, T., Bittner, W., Paschke, J.

The Astrophysical Institute Potsdam (AIP) and the Instituto de Astrofísica de Canarias (IAC) inaugurated the robotic telescopes STELLA-I and STELLA-II (STELLar Activity) on Tenerife on May 18, 2006. The observatory is located on the Izaa ridge at an elevation of 2400m near the German Vacuum Tower Telescope. STELLA consists of two 1.2m alt-az telescopes. One telescope fiber feeds a bench-mounted high-resolution echelle spectrograph while the other telescope feeds a wide-field imaging photometer. Both scopes work autonomously by means of artificial intelligence. Not only that the telescopes are automated, but the entire observatory operates like a robot, and does not require any human presence on site. Copyright © 2010 Klaus G. Strassmeier et al.

2020, Warmuth, A., Önel, H., Mann, G., Rendtel, J., Strassmeier, K.G., Denker, C., Hurford, G.J., Krucker, S., Anderson, J., Bauer, S.-M., Bittner, W., Dionies, F., Paschke, J., Plüschke, D., Sablowski, D.P., Schuller, F., Senthamizh Pavai, V., Woche, M., Casadei, D., Kögl, S., Arnold, N.G., Gröbelbauer, H.-P., Schori, D., Wiehl, H.J., Csillaghy, A., Grimm, O., Orleanski, P., Skup, K.R., Bujwan, W., Rutkowski, K., Ber, K.

The Spectrometer/Telescope for Imaging X-rays (STIX) is a remote sensing instrument on Solar Orbiter that observes the hard X-ray bremsstrahlung emission of solar flares. This paper describes the STIX Aspect System (SAS), a subunit that measures the pointing of STIX relative to the Sun with a precision of ±4′′, which is required to accurately localize the reconstructed X-ray images on the Sun. The operating principle of the SAS is based on an optical lens that images the Sun onto a plate that is perforated by small apertures arranged in a cross-shaped configuration of four radial arms. The light passing through the apertures of each arm is detected by a photodiode. Variations of spacecraft pointing and of distance from the Sun cause the solar image to move over different apertures, leading to a modulation of the measured lightcurves. These signals are used by ground analysis to calculate the locations of the solar limb, and hence the pointing of the telescope.