ORFEUS alignment concept

The alignment concept of ORFEUS, a short-term scientific space payload scheduled for launching by the STS in January 1993, is discussed. ORFEUS comprises two alternatively operating spectrometers (Echelle and Rowland) implemented in a CFC telescope with a 4-m tube length and an aperture of 1000 mm. The lightweight primary mirror has a focal length of 2426 mm. In order to achieve the required spectrometric high telescope resolution in the UV range (40-125 nm), a sophisticated alignment concept was developed. The centering of the alignment diaphragm (diameter: 15 microns) in the focus of the primary mirror has to be provided in the vertical tube position by means of an autocollimation telescope. The spectrometers have to be integrated into the horizontal telescope aligned within a special antigravity device to reduce optical surface deformations and to ensure the optical performance of the primary. The alignment of all optical components is to be performed in the visible spectral range.