In 2014 TNG also offered GIANO-B to the scientific community, providing a near-infrared (NIR) cross-dispersed echelle spectrograph covering 0.97 − 2.45 µm at a resolution of 50000. The possibility of simultaneously using GIANO-B together with the HARPS-N spectrograph (GIARPS observing mode) has been particularly appealing especially for the search of exoplanets by means high precision radial velocities. Moreover, GIANO-B triggered the possibility to observe in the NIR the Sun as a star by means of LOCNES, a solar telescope that feeds the spectrograph by a bundle of NIR fibers, for study the activity of the Sun as a star in the NIR wavelength range and its impact on the radial velocity measurements. Both science cases, include high-precision radial-velocity studies down to 3 m/s which demand for specialized, highly accurate wavelength calibration techniques. In this paper we present a developed absorption gas-cell to enable high-precision wavelength calibration for GIANO-B as a modified model of the CRIRES+ Absorbing Cell. We also discuss the manufacturing difficulties and the new design of the vessel. Furthermore, the AIT and the commissioning of the cells is also reported.
We describe the preliminary results of a ground-based observing campaign aimed at building a grid of approximately 200 spectro-photometric standard stars (SPSS), with an internal ≅1% accuracy (and sub-percent precision), tied to CALSPEC Vega and Sirius systems within ≅1%, for the absolute flux calibration of data gathered by Gaia, the European Space Agency (ESA) astrometric mission. The criteria for the selection and a list of candidates are presented, together with a description of the survey's strategy and the adopted data analysis methods. All candidates were also monitored for constancy (within ±5 mmag, approximately). The present version of the grid contains about half of the final sample, it has already reached the target accuracy but the precision will substantially improve with future releases. It will be used to calibrate the Gaia (E)DR3 release of spectra and photometry.
LOCNES (LOw-Cost NIR Extended Solar telescope) is a solar telescope installed at the TNG (Telescopio Nazionale Galileo). It feeds the light of the Sun into the NIR spectrograph GIANO-B through a 40-m patch of optical fibers. LOCNES has been designed to obtain high signal-to-noise ratio spectra of the Sun as a star with an accurate wavelength calibration through molecular-band cells. This is an entirely new area of investigation that will provide timely results to improve the search of telluric planets with NIR spectrographs such as iSHELL, CARMENES, and GIANO-B. We will extract several disc-integrated activity indicators and average magnetic field measurements for the Sun in the NIR. Eventually, they will be correlated with both the RV of the Sun-as-a -star and the resolved images of the solar disc in visible and NIR. Such an approach will allow for a better understanding of the origin of activity-induced RV variations in the two spectral domains and will help in improving the techniques for their corrections. In this paper, we outline the science drivers for the LOCNES project and its first commissioning results.
GIANO-B is the high resolution near-infrared (NIR) spectrograph of the Telescopio Nazionale Galileo (TNG), which started its regular operations in October 2017. Here we present GIANO-B Online Data Reduction Software (DRS) operating at the Telescope.
GIANO-B Online DRS is a complete end-to-end solution for the spectrograph real-time data handling. The Online DRS provides management, processing and archival of GIANO-B scientific and calibration data. Once the instrument control software acquires the exposure ramp segments from the detector, the DRS ensures the complete data flow until the final data products are ingested into the science archive. A part of the Online DRS is GOFIO software, which performs the reduction process from ramp-processed 2D spectra to extracted and calibrated 1D spectra.
A User Interface (UI) developed as a part of the Online DRS provides basic information on the final reduced data, thus allowing the observer to take decisions in real-time during the night and adjust the observational strategy as needed.
GIANO is the IR high resolution spectrograph of the TNG. It covers the 950-2450 nm wavelengths range in a single shot at a resolving power of R=50,000. This document describes the first fundamental steps of the data reduction, namely eliminating the curvature of the traces and the tilt of the slit images. These effects can be accurately modeled and corrected using a physical model of the instrument. We find that the curvature and tilt parameters did not vary during the whole lifetime of the instrument. In particular, they were not affected by thermal cycles or by the works performed to mount the spectrometer on its new interface. A similar ab-initio modeling is also applied to the wavelength calibration that can be accurately (0.03 pixel r.m.s.) defined using a minimum number of parameters to fit. This approach is particularly useful when using a calibration source with an irregular wavelengths coverage; e.g. for the U-Ne lamp that has only few lines in the 2000 nm - 2300 nm wavelengths range.
GIARPS (GIAno and haRPS) is a project devoted to have on the same focal station of the Telescopio Nazionale Galileo (TNG) both high resolution spectrographs, HARPS–N (VIS) and GIANO–B (NIR), working simultaneously. This could be considered the first and unique worldwide instrument providing cross-dispersed echelle spectroscopy at a resolution of 50,000 in the NIR range and 115,000 in the VIS and over in a wide spectral range (0.383−2.45 μm) in a single exposure. The science case is very broad, given the versatility of such an instrument and its large wavelength range. A number of outstanding science cases encompassing mainly extra-solar planet science starting from rocky planets search and hot Jupiters to atmosphere characterization can be considered. Furthermore both instruments can measure high precision radial velocities by means the simultaneous thorium technique (HARPS–N) and absorbing cell technique (GIANO–B) in a single exposure. Other science cases are also possible. GIARPS, as a brand new observing mode of the TNG started after the moving of GIANO–A (fiber fed spectrograph) from Nasmyth–A to Nasmyth–B where it was re–born as GIANO–B (no more fiber feed spectrograph). The official Commissioning finished on March 2017 and then it was offered to the community. Despite the work is not finished yet. In this paper we describe the preliminary scientific results obtained with GIANO–B and GIARPS observing mode with data taken during commissioning and first open time observations.
KEYWORDS: Signal to noise ratio, Spectrographs, Sensors, Calibration, Spectroscopy, Lamps, Data processing, Infrared radiation, Near infrared spectroscopy, Signal detection
The NIR echelle spectrograph GIANO-B at the Telescopio Nazionale Galileo is equipped with a fully automated online DRS: part of this pipeline is the GOFIO reduction software, that processes all the observed data, from the calibrations to the nodding or stare images. GOFIO reduction process includes bad pixel and cosmic removal, flat-field and blaze correction, optimal extraction, wavelength calibration, nodding or stare group processing. An offline version of GOFIO will allow the users to adapt the reduction to their needs, and to compute the radial velocity using telluric lines as a reference system. GIANO-B may be used simultaneously with HARPS-N in the GIARPS observing mode to obtain high-resolution spectra in a wide wavelength range (383-2450 nm) with a single acquisition. In this framework, GOFIO, as part of the online DRS, provides fast and reliable data reduction during the night, in order to compare the infrared and visible observations on the fly.
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