Catálogo de publicaciones - libros

Sketching the beam layout of the Cologne Tunable Heterodyne Infrared Spectrometer (THIS), the basic principle of operation of a heterodyne receiver is illustrated in Fig. 1 [1,2]. A local oscillator (LO) is precisely locked to a frequency close to the observing wavelength by the resonance of a Fabry-Perot diplexer, which itself is stabilised to a resonance of a special HeNe laser. The LO radiation with its known frequency is then superimposed onto the signal of the observed science source (or hot or cold calibration sources) and both get mixed via a HgCdTe (MCT) detector, what generates a beat frequency (intermediate frequency; IF) at a much lower (and therefore easier to process) frequency of about 1 GHz. This broadband low frequency signal, which still contains all the spectral information of the science source, can then be analysed using common broadband Acousto Optical Spectrometers (AOS).

The far-infrared (FIR) wavelength regime is of prime importance for astrophysics. The study of ionic, atomic and molecular lines, many of them present in the FIR, provides important and unique information on the star and planet formation process occurring in interstellar clouds, and the lifecycle of gas and dust in general. As these regions are heavily obscured by dust, FIR observations are the only means of getting insight in the physical conditions and chemistry. These investigations require high spectral as well as high angular resolution in order to match the small angular sizes of star forming cores and circumstellar disks. ESPRIT provides , in a wavelength regime not accessible to ALMA (Atacama Large Millimeter Array) nor to JWST (James Webb Space Telescope).

The Large Binocular Telescope (LBT) consists of two 8.4 m mirrors on one mechanical mounting, with a center to center separation of 14.4 m. In the combined, focus the LBT provides the spatial resolution of a 23 m telescope and the sensitivity of a 12 m telescope. We are building an instrument called LINC-NIRVANA using the capability of LBT in Fizeau mode (imaging interferometry), leading to a unique combination of spatial resolution, sensitivity and field of view. The instrument will prove technology, such as Multi-Conjugated Adaptive Optics, which is needed for the next generation of Extremely Large Telescopes (ELT) (20 to 100 m diameter). The capabilities of LINC-NIRVANA will extend science, especially for extragalactic programs, building a bridge between current 10 m class telescopes and ELTs.

The Multi Unit Spectroscopic Explorer (MUSE) is a second generation instrument [1] in development for the Very Large Telescope (VLT) of the European Southern Observatory (ESO). It is a panoramic integral-field spectrograph operating in the visible wavelength range. It combines a wide field of view with the improved spatial resolution provided by adaptive optics and covers a large simultaneous spectral range. MUSE couples the discovery potential of an imaging device to the measuring capabilities of a spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes it a unique and powerful tool for discovering objects that cannot be found in imaging surveys. MUSE is optimized for the study of the progenitors of normal nearby galaxies out to very high redshift. It will also allow detailed studies of nearby normal, starburst and interacting galaxies, and of galactic star formation regions.

Four projects exploiting Multi Conjugate Adaptive Optics with Layer-Oriented wavefront sensing technique are being developed by our group in this period. The purpose of these projects is, in some cases, to give experimental evidence to the Layer-Oriented concept, developed in the last few years. In some other cases, to build real facilities to be used in 8-m class telescopes, like VLT in Chile or LBT in Arizona. A brief description of these project will be given while indeed an analysis of the possible scientific outcome which can be obtained when reaching diffraction limit images in the near infrared using MCAO will be performed.

The present article attempts to address the question of the role of optical and infrared interferometry in the era of Extremely Large Telescopes (ELTs). A strawman concept for an Extremely Large Synthesis Array (ELSA) could consist of 27 ten-meter telescopes and baselines of up to 10km [1] (see also Tab. 1). It appears that ELSA could be built today with existing technologies, but the cost would probably be prohibitively high. A technology roadmap for ELSA must therefore provide solutions that are not only , but also . In this context it will be interesting to explore to which extent costreduction approaches that are being investigated for the design and construction of large monolithic telescopes – such as the OWL concept – can also be applied to ELSA.

High-resolution interferometric imaging at optical and infrared wavelengths provides unique information for the study of many different classes of astronomical objects. A large number of key objects have been resolved with unprecedented resolution using bispectrum speckle interferometry or infrared long-baseline interferometry. IR interferometry allows the study of, for example, disks and out- flows of YSOs (e.g., [1]), the wavelength and phase-dependent size of evolved stars (e.g., [2]), as well as the structure of AGN. The ESO Very Large Telescope Interferometer with its AMBER phase-closure instrument will enable us to achieve the spectacular resolution of 1 mas at the wavelength of 1 micron. The science goals of AMBER include studies of the jet structure of YSOs, the interferometric detection of extra-solar planets as well as the resolution of tori and broad-line regions of AGN.

GLAST-LAT is a telescope for gamma rays in the range 20MeV÷300 GeV. It consists of a Silicon Strip Detectors (SSDs) Tracker, a CsI calorimeter and an anticoincidence detector. The total surface of silicon detectors is almost 80m so it will have the largest equipped area among all space experiments. In this paper will be presented the electrical and dimensional tests performed on all the flight SSDs and the ladders assembly procedures and the electrical and geometrical tests on the first flight sensor produced.

A test sequence that involves functional verification and mechanical - thermal properties of the GLAST LAT Tracker has been done, first on Engineering model prototypes, and it will continue on flight hardware. The results of vibration and thermal vacuum tests on the Engineering Model Tower of the GLAST LAT Tracker are presented. The performance expected for silicon detectors as a function of operating temperatures in the mission environment have also been investigated and described.

The Large Cherenkov Array is a concept for a γ-ray instrument in the 15 GeV to 1TeV energy range, optimized for Fundamental Physics and Cosmology, with signicant capabilities in Astrophysics. It is based on a 16-20 Cherenkov telescope array, with ~ 18m diameter, located at high altitude (5000 m; possibly on Chajnantor).