X-shooter is the first 2nd generation instrument of the ESO Very Large Telescope (VLT). It is a very efficient, single-target, intermediate-resolution spectrograph that was installed at the Cassegrain focus of UT2 in 2009. The instrument covers, in a single exposure, the spectral range from 300 to 2500 nm. It is designed to maximize the sensitivity in this spectral range through dichroic splitting in three arms with optimized optics, coatings, dispersive elements and detectors. It operates at intermediate spectral resolution (R ∼ 4000−17 000, depending on wavelength and slit width) with fixed échelle spectral format (prism cross-dispersers) in the three arms. It includes a 1.8 × 4 integral field unit as an alternative to the 11 long slits. A dedicated data reduction package delivers fully calibrated two-dimensional and extracted spectra over the full wavelength range. We describe the main characteristics of the instrument and present its performance as measured during commissioning, science verification and the first months of science operations.

The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. ?? 2013 Elsevier B.V. All rights reserved

The definition and optimization studies for the Gaia satellite spectrograph, the ‘radial velocity spectrometer’ (RVS), converged in late 2002 with the adoption of the instrument baseline. This paper reviews the characteristics of the selected configuration and presents its expected performance. The RVS is a 2.0 × 1.6 degree integral field spectrograph, dispersing the light of all sources entering its field of view with a resolving power R=λ/Δλ= 11 500 over the wavelength range [848, 874] nm. The RVS will continuously and repeatedly scan the sky during the 5‐yr Gaia mission. On average, each source will be observed 102 times over this period. The RVS will collect the spectra of about 100–150 million stars up to magnitude V≃ 17–18. At the end of the mission, the RVS will provide radial velocities with precisions of ∼2 km s−1 at V= 15 and ∼15–20 km s−1 at V= 17, for a solar‐metallicity G5 dwarf. The RVS will also provide rotational velocities, with precisions (at the end of the mission) for late‐type stars of σvsin i≃ 5 km s−1 at V≃ 15 as well as atmospheric parameters up to V≃ 14–15. The individual abundances of elements such as silicon and magnesium, vital for the understanding of Galactic evolution, will be obtained up to V≃ 12–13. Finally, the presence of the 862.0‐nm diffuse interstellar band (DIB) in the RVS wavelength range will make it possible to derive the three‐dimensional structure of the interstellar reddening.