Giant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in the mid-infrared can be mitigated, then exoplanets with lower masses can also be imaged. Here we present a ground-based mid-infrared observing approach that enables imaging low-mass temperate exoplanets around nearby stars, and in particular within the closest stellar system, α Centauri. Based on 75–80% of the best quality images from 100 h of cumulative observations, we demonstrate sensitivity to warm sub-Neptune-sized planets throughout much of the habitable zone of α Centauri A. This is an order of magnitude more sensitive than state-of-the-art exoplanet imaging mass detection limits. We also discuss a possible exoplanet or exozodiacal disk detection around α Centauri A. However, an instrumental artifact of unknown origin cannot be ruled out. These results demonstrate the feasibility of imaging rocky habitable-zone exoplanets with current and upcoming telescopes.

The powder bed additive manufacturing process selective laser melting (SLM) enables designers and engineers to overcome restrictions of conventional manufacturing technologies. The potential of fabricating complex lightweight structures and processing advanced materials is a key feature for enhancing further development of high performance components for space applications. Due to a high specific stiffness and a thermal expansion coefficient very close to electroless nickel, which is an advantageous optical coating material, the hypereutectic aluminum-silicon alloy AlSi40 shows great potential for the manufacturing of optical mirrors for space applications. In prior investigations, Hilpert et al. showed the feasibility to process AlSi40 by SLM [E. Hilpert and S. Risse, Materials Science & Technology Conference and Exhibition MS&T'15, Columbus, Ohio, 4–8 October 2015 (Association for Iron & Steel Technology, Warrendale, PA, 2015) and E. Hilpert, “Struktur und Eigenschaften von additiv gefertigten hypereutektischen Aluminum-Siliciumlegierungen,” in Werkstoffwoche 2017, Dresden, Germany, 28 September 2017 (Deutsche Gesellschaft für Materialkunde e.V., Berlin, 2017)]. Nevertheless, in order to qualify this material for space applications, the manufacturing process and fabricated samples need to be thoroughly investigated in terms of microstructural, mechanical, as well as thermo-physical characterization. The authors present results of the SLM process development for manufacturing dense AlSi40 samples with a relative density above 99.50%. The effect of various process parameters, such as hatch distance, preheating, and scanning strategy, on the formation of defects was investigated by destructive [e.g., optical microscopy (OM)] and nondestructive (e.g., computed tomography) testing. In addition, the effect of several thermal post-treatments on the AlSi40 microstructure was profoundly analyzed by multiple methods such as OM, scanning electron microscopy, and energy dispersive x-ray spectroscopy analysis. Moreover, mechanical and thermo-physical testing of manufactured specimens was conducted to provide material characteristics for component design. In conclusion, the determined material properties of AlSi40 samples fabricated by SLM were compared to bulk material properties. The gained knowledge and testing data were evaluated in order to identify correlations and dependencies.

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The World Space Observatory Ultraviolet (WSO-UV) is a multi-national project lead by the Russian Federal Space Agency (Roscosmos) with the objective of high performance observations in the ultraviolet range. The 1.7 m WSO-UV telescope is equipped with UV spectrographs (responsibility of Russia and Germany) and UV imagers (responsibility of Spain). The UV spectroscopic instrumentation comprises two high resolution echelle spectrographs operating in wavelength ranges of 102-176 nm and 174-310 nm respectively, and a Long Slit Spectrograph designed to operate in the range of 102-310 nm. All three spectrographs represent individual instruments. In order to save mass while maintaining high stiffness, the instruments are combined to a monoblock, World Space Observatory Ultraviolet Spectrographs (WUVS). Due to strict technical requirements stated by the customer the material CeSiC (provided by the company ECM) has been selected for the design of the spectrograph structure. In contrast to aluminium, the stable structure of CeSiC is significantly less sensitive to thermal gradients. No further mechanism for focus correction with high functional, technical and operational complexity and corresponding additional System costs are necessary. Using CeSiC also relaxes the thermal control requirements of ±5°C, which represents a considerable cost driver for the S/C design. The phase B2 study of the WUVS instrument finished in December 2010 in collaboration with Russia and with industrial support of the Kayser-Threde company. It included construction of a Structural Thermal Model (STM) for verification of thermal and mechanical loads, stability with respect to thermal distortions and CeSiC manufacturing feasibility.

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