The XEUS mission is conceived as Europe's next generation X-ray space observatory aiming at the detection and
spectroscopy of faint astronomical sources located at high red-shift. With unprecedented sensitivity to the million-degree
hot universe, XEUS is supposed to explore key areas of contemporary astrophysics. Due to the considerable telescope
focal length of 35 m, the mission profile foresees two separate spacecraft, one carrying the mirrors, the other one
carrying the detectors, flying in precise formation as if connected by a rigid telescope tube. The paper presents an
innovative light-weight X-ray telescope design and its predicted performance as resulting from a recent study on XEUS
Telescope Accommodation funded by the European Space Agency ESA. The main challenge of this work was to find a
telescope concept compatible with the Ariane V launcher constraints while meeting highly demanding optical
performance requirements.
The optical and thermal design of the 1.5 m solar telescope GREGOR is presented. The three first main mirrors of GREGOR will be made from Cesic, a silicon carbide material. One major constraint of large solar telescopes is the thermal load of the structure and the mirrors. The mirrors are heated by the solar radiation and introduce potentially harmful mirror seeing. GREGOR will use an active mirror cooling system and an open telescope structure to reduce these negative effects. A thermal analysis shows that the equilibrium temperature of the Cesic Mirror without active cooling is 6° above ambient temperature. Additional cooling will reduce the temperature difference of the optical surface and ambient air to below 0.1° K. With tempered airflow (about 2.5 m3/s per square meter mirror surface) the temperature gradient on the surface of the face sheet is less than 0.1°K. The telescope will have an open structure and a complete retractable dome to support mirror and structure cooling by wind.
Ceramics technologies were successfully applied to a series of lightweight mirrors with different sizes and requirements. Several joining and optical surface optimizations were applied. Besides the classical rib-structured mirrors also the application of sandwich mirrors with Cesic foam and/or honeycomb structures are going to be tested. For all processes relatively simple straightforward processes can be applied which keeps the products relatively cost-effective.
Ceramic mirrors and complex structures are becoming more important for high-precision lightweighted optomechanical applications. Carbon-fiber reinforced silicon carbon (C/SiC) is a composite ceramic material consisting of SiC as its major constituent. Developments over the past 10 years by IABM, ECM, and Astrium GhbH have demonstrated the feasibility and versitility of this ceramic material for different applications.
Furthermore, Cesic-a trademark of ECM for C/SiC- allows relatively quick and cheap manufacturing of components because the components can be shaped with conventional tools in a milling and/or drilling process of the greenbody material. Through a joining process and our new development of optical surfaces based on a slurry cladding technology, Cesic allows for a direct up-scaling of structures and optical surfaces to large size applications and systems. The size of the structures and mirrors that can be manufactured is limited only by the scale of the available production facilities, the largest of which currently is 2.4 m in diameter.
Ceramic mirrors and complex structures are becoming more important for high precision lightweighted optomechanical applications. Carbon-fiber reinforced silicon carbon (C/SiC) is a composite ceramic material consisting of SiC as its major constituent. Developments over the past 10 years by IABG, ECM, and Astrium GmbH have demonstrated the feasibility and versatility of this ceramic material for different applications. The most favourable characteristics of the material are high stiffness, high thermal conductivity and low thermal expansion (CTE). Furthermore, Cesic -- a trademark of ECM for C/SiC -- allows relatively quick and cheap manufacturing of components because the components can be shaped with conventional tools in a milling and/or drilling process of the greenbody material. Through a joining process and our new development of optical surfaces based on a slurry cladding technology, CesicR allows for a direct up-scaling of structures and optical surfaces to large size applications and systems. The size of the structures and mirrors that can be manufactured is limited only by the scale of the available production facilities, the largest of which currently is 2.4 m in diameter.
Ceramic mirrors are going to become more and more attractive for realizing lightweight optomechanical systems. The C/SiC ceramic described in this article, a joint development of DSS and IABG offers design freedom through a novel straight forward manufacturing process, combined with excellent optomechanical properties. This process not only enables to build ultra lightweight mirrors of very high complexity, but also very large 3d-structures. Mirrors up to 80 cm and structures up to 2.5 m have been realized. The paper will summarize the recent progress achieved in producing mirror blanks up to 1 m diameter and beyond. Recent results in new technologies for achieving high performance optical surfaces will be reported. An outlook for future envisaged applications of C/SiC technology, e.g. 2.5 m mirror segments for the next generation of large earth and space based telescopes, is given.
Gerhard Schmidtke, E. Neske, Helmut Becker-Ross, Stefan Florek, H. Fahr, M. Roemer, N. Jakowski, D. Klaehn, Y. Kotov, Gerhard Kraemer, M. Paetzold, Norbert Pailer, K. Pflug
Long-term radiometric accuracy is a fundamental requirement for future measurement of solar and terrestrial atmospheric EUV emissions from space. Since remote sensing of EUV radiation will become an important measuring technique to explore the thermosphere, new methods have to be established to trace calibration changes of EUV instrumentation, too. With the proposed satellite ATON (Egyptian god of the sun) the solar energy input and other important thermospheric/ionospheric parameters (O2, O, O+, N2, N+, NO, H, He, Ne, Tn, X-rays, solar EUV energy, polar energies) shall be measured based on absolute in-flight calibration of solar and airglow instrumentation. The model payload consists of (1) auto-calibrating solar EUV spectrometers, (2) airglow-solar spectrometer, (3) airglow spectrometer (high spectral resolution), (4) EUV photometers (high data statistics), (5) radio beacon experiment and (6) photocathode arrangement (the latter to detect short-lived solar phenomena of aeronomic interest). The basic measuring concept and instrumental details are presented.
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