An overview and the current status of instrumentation at the Large Binocular Telescope Observatory

Abstract

An overview of instrumentation for the Large Binocular Telescope (LBT) is presented. Optical instrumentation includes the Large Binocular Camera (LBC), a pair of wide-field (24 ′ × 24 ′ ) mosaic CCD imagers at the prime focus, and the Multi-Object Double Spectrograph (MODS), a pair of dual-beam blue-red optimized long-slit spectrographs mounted at the left and right direct F/15 Gregorian foci incorporating multiple slit masks for multi-object spectroscopy over a 6 ′ field and spectral resolutions of up to 2000. Infrared instrumentation includes the LBT Near-IR Spectrometer (LUCI), a modular near-infrared (0.9-2.5 µm) imager and spectrograph pair mounted at the left and right front-bent F/15 Gregorian foci and designed for seeing-limited (FOV: 4 ′ × 4 ′ ) imaging, long-slit spectroscopy, and multi-object spectroscopy utilizing cooled slit masks and diffraction limited (FOV: 0 ′ .5 × 0 ′ .5) imaging and long-slit spectroscopy. Strategic instruments under development that can utilize the full 23 m baseline of the LBT include an interferometric cryogenic beam combiner with near-infrared and thermal-infrared instruments for Fizeau imaging and nulling interferometry (LBTI) and an optical bench nearinfrared beam combiner utilizing multi-conjugate adaptive optics for high angular resolution and sensitivity (LINC-NIRVANA). LBTI is currently undergoing commissioning and performing science observations on the LBT utilizing the installed adaptive secondary mirrors in both single-sided and two-sided beam combination modes. In addition, a fiber-fed bench spectrograph (PEPSI) capable of ultra high resolution spectroscopy and spectropolarimetry (R = 40,000-300,000) will be available as a principal investigator instrument. Installation and testing of the bench spectrograph will begin in July 2014. Over the past four years the LBC pair, LUCI1, and MODS1 have been commissioned and are now scheduled for routine partner science observations. Both LUCI2 and MODS2 passed their laboratory acceptance milestones in the summer of 2013 and have been installed on the LBT. LUCI2 is currently being commissioned and the data analysis is well underway. Diffraction-limited commissioning of its adaptive optics modes will begin in the 2014B semester. MODS2 commissioning began in May 2014 and will completed in the 2014B semester as well. Binocular testing and commissioning of both the LUCI and MODS pairs will begin in 2014B with the goal that this capability could be offered sometime in 2015. The availability of all these instruments mounted simultaneously on the LBT permits unique science, flexible scheduling, and improved operational support.

Towards controlled Fizeau observations with the Large Binocular Telescope

“…LBTI (with the current NIC cryostat [18]) obtained the first AO-corrected (but not phase-controlled) Fizeau images with LMIRcam and NOMIC in April and May 2012 [21]. Finally, K S -band phase-tracking with Phasecam was coupled to the nulling mode beginning in December 2013 [23].…”

Revisiting the comparison between the Shack-Hartmann and the pyramid wavefront sensors via the Fisher information matrix

“…High contrast imaging on large ground based telescopes therefore implies adaptive optics (AO) to correct for atmospheric turbulence and aberrations due to the optical system itself. The tight requirements on the amplitude of the residual wavefront lead to high-order AO systems, typically from 30×30 actuators to 44×44 actuators on current systems [1][2][3]. The association of high-order AO with coronagraphy, and more generally high contrast instruments, is generally called eXtreme AO (XAO) [4].…”

“…We consider three wavefront sensing approaches: the classical Shack-Hartmann sensor, widely used in AO, and recently implemented in two operational XAO systems SAXO [1] and GPI [2]; the pyramid wavefront sensor, introduced in 1996 by Ragazzoni [19], very promising for high-order AO, and successfully integrated in FLAO [3], the LBT high-order AO system; the LIFTed Shack-Hartmann sensor [20], a recent attractive evolution of the Shack-Hartmann dedicated to high order sensing and that makes use of the LIFT concept [21].…”

Infrared photometry with 'wall-eyed' pointing at the Large Binocular Telescope

“…LBTI is a NASA-funded, PI-run instrument [13][14][15] that combines the infrared light from the two beams at a common focus inside a beam combiner, 16 and feeds the light into a cryogenic instrument. As a direct imager, LBTI can use both apertures to have the light-collecting power equivalent to a single 11.8 m aperture.…”