Astronomical instrumentation

Abstract:

We describe the implementation of differential wavefront sampling(DWS) in optical alignment of a pupilsegmented telescope system. As a wavefront-based optical alignment method, DWS can efficiently provide estimations of misalignments present in an optical system by deliberately perturbing optical elements in a systematic manner. This has been demonstrated in our previous numerical studies with realistic uncertainties in wavefront measurements, motion control, and optical surface deformations, suggesting that the method has potential in optical alignment and phasing of pupil-segmented systems such as the future Extremely Large Telescopes (ELTs). The basic idea and procedures of DWS are first described. We then present and discuss preliminary simulations using the currently proposed European Extremely Large Telescope (E-ELT) as an example system.

Abstract:

The UK FMOS spectrograph forms part of Subaru's FMOS multi-object infrared spectroscopy facility. The spectrograph was shipped to Hilo in component form in August of 2007. We describe the integration sequence for the spectrograph, the results of cooldown tests using a new chiller unit fitted to the spectrograph at the telescope, and alignment tests of the spectrograph, gratings and OH-suppression masks. We present the first-light observations for the spectrograph from May 2008.

Abstract:

The heart of the KMOS instrument is a complex optical system with over 300 separate optical paths. The optical design is spread between 4 sub-systems which have been designed at three different institutions. In order that the end to end performance of the final design can be monitored and controlled it is necessary to specify the performance and interface requirements of each sub-system clearly. This paper describes the parameters that were necessary to control so that the sub-system designs could be carried out independently while maintaining visibility and control of the end to end performance. The method of apportioning the budgets between the sub-systems and the modeling performed to verify compliance is also described.

Abstract:

CanariCam is the facility mid-infrared (MIR) instrument for the Gran Telescopio Canarias (GTC), a 10.4m telescope at the Observatorio del Roque de los Muchachos on La Palma. One of the science drivers for Canari-Cam is the study of active galactic nuclei (AGN). We will exploit the instrument's high sensitivity in imaging,spectroscopy, and polarimetry modes to answer fundamental questions of AGN and their host galaxies. Dust in the nucleus of an active galaxy reprocesses the intrinsic radiation of the central engine to emerge in the MIR. Current work demonstrates that the hot dust immediately associated with the AGN, which blocks direct views of the AGN from some lines of sight, is con.ned to small (parsec) scales. Thus, high spatial resolution is essential to probe the "torus" of unified AGN models separate from the host galaxy. CanariCam provides a 0.08- pixel scal e for Nyquist sampling the diffraction-limited point spread function at 8μm, and narrow (0.2-) spectroscopy slits (with R=120-1300). New observations with the GTC/CanariCam will provide key constraints on the physical conditions in the clumpy torus, and we will sensitively determine AGN obscuration as a function of nuclear activity. We will therefore address the fueling process and its relationship to the torus, the interaction with the host galaxy, and dust chemistry. These data will be essential preparation for the next generation of telescopes that will observe the distant universe directly to explore galaxy and black hole formation and evolution, and the GTC/CanariCam system uniquely provides multiple modes to probe AGN.

Abstract:

One of the main science objectives of the European ELT is the direct imaging of extrasolar planets. The large aperture of the telescope has the potential to significantly enlarge the discovery space towards older gas giant exo-planets seen in reflected light. In this paper, we give an overview of the EPICS system design strategy during the phase A study. In order to tackle the critical limitations to high contrast, extensive end-to-end simulations will be developed since the start to test different scenarios and guide the overall design. Keywords: Extremely Large Telescope, high contrast imaging, extrasolar planets, instrumentation, adaptive optics.