The near-infrared GRAVITY instrument has become a fully operational spectro-imager, while expanding its capability to support astrometry of the key Galactic Centre science. The mid-infrared MATISSE instrument has just arrived on Paranal and is starting its commissioning phase. NAOMI, the new adaptive optics for the Auxiliary Telescopes, is about to leave Europe for an installation in the fall of 2018. Meanwhile, the interferometer infrastructure has continuously improved in performance, in term of transmission and vibrations, when used with both the Unit Telescopes and Auxiliary Telescopes. These are the highlights of the last two years of the VLTI 2nd generation upgrade started in 2015.
ESO is undertaking a large upgrade of the infrastructure on Cerro Paranal in order to integrate the 2nd generation of interferometric instruments Gravity and MATISSE, and increase its performance. This upgrade started mid 2014 with the construction of a service station for the Auxiliary Telescopes and will end with the implementation of the adaptive optics system for the Auxiliary telescope (NAOMI) in 2018. This upgrade has an impact on the infrastructure of the VLTI, as well as its sub-systems and scientific instruments.
The New Adaptive Optics Module for Interferometry (NAOMI) will be developed for and installed at the 1.8-metre Auxiliary Telescopes (ATs) at ESO Paranal. The goal of the project is to equip all four ATs with a low-order Shack– Hartmann adaptive optics system operating in the visible. By improving the wavefront quality delivered by the ATs for guide stars brighter than R = 13 mag, NAOMI will make the existing interferometer performance less dependent on the seeing conditions. Fed with higher and more stable Strehl, the fringe tracker(s) will achieve the fringe stability necessary to reach the full performance of the second-generation instruments GRAVITY and MATISSE.
The present work is an attempt to characterize the performances of SINFONI, how we follow the history line of its key parameters and detect possible problems. We will make a review of the health check, with analysis of the long term trends. We will analyze the transfer function of the system during the calibrations and on sky, and evaluate their sensitivity and relation to external parameters. The study of the trends of the key parameters of the instrument provides useful analysis and monitoring to determine when an instrument eventually starts to degrade or to trace in time the different events in its maintenance. One can also determine when a major intervention or upgrade of the system might be necessary, where to focus the efforts to maximize the gain versus the work performed, and provides useful information on the status of the instrument prior to the intervention.
The atmospheric optical turbulence profile, the strength of the turbulence as a function of altitude above the ground, can
be used to determine the seeing statistics of a particular site. This information is useful for optimizing the tomographic
process in Adaptive Optics systems and for characterizing the performance. In this paper, we describe a method to
estimate the atmospheric turbulence profile based on the telemetry data coming out of GeMS, a Multi Conjugated
Adaptive Optics (MCAO) instrument installed on the Gemini South telescope. The method is based on the SLODAR
technique (SLOpe Detection and Ranging), where the wavefront slopes from two stars angularly separated on the sky are
measured, and their cross-correlation is used to retrieve the atmospheric optical profile. We have modified the classical
SLODAR method and adapted it for the closed loop, multiple laser guide stars case. In this paper we present our method,
validation of it in simulation, and its application for on-sky data.
Multiple Application Curvature Adaptive Optics (MACAO) systems are used at the coud´e focus of the unit
telescopes (UTs) at the La-Silla Paranal Observatory, Paranal, to correct for the wave-front aberrations induced
by the atmosphere. These systems are in operation since 2005 and are designed to provide beams with 10 mas
residual rms tip-tilt error to the VLTI laboratory. We have initiated several technical studies such as measuring
the Strehl ratio of the images recorded at the guiding camera of the VLTI, establishing the optimum setup of
the MACAO to get collimated and focused beam down to the VLTI laboratory and to the instruments, and
ascertaining the data generated by the real time computer, all aimed at characterizing and improving the overall
performance of these systems. In this paper we report the current status of these studies.
The ESO Very Large Telescope Interferometer (VLTI) offers access to the four 8-m Unit Telescopes (UT) and the four
1.8-m Auxiliary Telescopes (AT) of the Paranal Observatory located in the Atacama Desert in northern Chile. The two
VLTI instruments, MIDI and AMBER deliver regular scientific results. In parallel to the operation, the instruments
developments are pursued, and new modes are studied and commissioned to offer a wider range of scientific possibilities
to the community. New configurations of the ATs array are discussed with the science users of the VLTI and
implemented to optimize the scientific return. The monitoring and improvement of the different systems of the VLTI is a
continuous work. The PRIMA instrument, bringing astrometry capability to the VLTI and phase referencing to the
instruments has been successfully installed and the commissioning is ongoing. The possibility for visiting instruments
has been opened to the VLTI facility.