Self-Calibrated Interferometry For exoplanet spectrscopY (SCIFY) is the name of a new ERC Consolidator project that will start in October 2020 at KU Leuven. SCIFY aims at building NOTT, a thermal near-infrared (3.8 microns) high-contrast nulling interferometric instrument for the visitor focus of the Very Large Telescope Interferometer. By leveraging its state-of-the-art infrastructure, long baselines, and strategic position in the Southern hemisphere, a dedicated high-contrast VLTI instrument will be able to carry out several exoplanet programmes to study young Jupiter-like exoplanets at the most relevant angular separations (i.e., close to the snow line) and better understand how planets form and evolve. In the long term, the SCIFY project will be a cornerstone in the roadmap leading to the characterisation of terrestrial exoplanets and the search for life beyond Earth (see LIFE project page).
The immediate objectives of SCIFY will focus on the following research topics:
- Development, characterization, and tests of the instrument in the lab. One of the main tasks of SCIFY is to build the Hi-5 interferometric instrument. In collaboration with different universities (University of Liège, Australian National University, University of Cologne, Institut de planétologie et d'astrophysique de Grenoble, Nice Observatory, ETH Zurich), we will build, characterize, and test the new instrument in the laboratory. With the support of engineers at the Liege Space Center, the main tasks will consist in designing the cryostat, integrating the detector, aligning the instrument, testing different achromatic phase shifters, comparing different beam combination strategies, and developing the control and data acquisition software.
- Development of advanced self-calibration data reduction techniques. Current state-of-the-art nulling interferometers are still operating one to two orders of magnitudes above the fundamental photon noise limit due to systematic errors caused by imperfect background subtraction and/or residual phase variation. With SCIFY, we will tackle this problem by improving self-calibration data processing techniques in three different ways: (1) add the possibility to process spectrally dispersed data (spectral self-calibration) and investigate how to use the constructive output of the interferometer to remove residual starlight and telluric absorption from the destructive output; (2) generalise the self-calibration algorithm to handle more than two telescopes; and (3) adapt the technique to classical phase-referenced stellar interferometers such as VLTI/GRAVITY (in collaboration with NASA/JPL). The goal is to provide a new and more robust general purpose interferometric self-calibration data reduction tool while preparing the data processing tool of NOTT.
- Enabling deep interferometric nulling with the VLTI. Within SCIFY, we will develop control solutions to improve the stability and robustness of the VLTI against internal and external optical path-length difference (OPD) variations. Current nulling interferometers are limited by both the dispersive effect of precipitable water vapor (PWV) and by high-frequency vibration peaks, which are also present on the VLTI infrastructure. In collaboration with the GRAVITY+ collaboration and ESO, we will design and optimise a system to monitor and remove these perturbations with the goal to improve the OPD stability of the VLTI. We will also investigate the possibility to use the constructive output of the nuller in order to track and correct the low frequency variations induced by PWV.
- Combination of nulling interferometry and high-dispersion spectroscopy. Combining high-dispersion-spectroscopy and direct imaging has proven to be a powerful technique to improve the dynamic range and characterize exoplanets with single-dish telescopes. In collaboration with the Institut de planétologie et d'astrophysique de Grenoble, we will establish the mathematical foundations of combining nulling interferometry and high-dispersion spectroscopy and investigate how it improves the dynamic range.
- Scientific exploitation of high-contrast infrared interferometers. Our team participates in the scientific exploitation of the second-generation instruments on the VLTI (GRAVITY and MATISSE). In particular, we currently lead and/or are part of various observing programmes to characterize exozodiacal dust around nearby main-sequence stars. Thanks to our collaborations with various observatories around the world, we also have access to data obtained with state-of-the-art nulling interferometers (LBTI, Keck). Within SCIFY, we will continue to contribute to their scientific exploitation and support their data analysis efforts. By 2024, the goal is to start the scientific exploitation of NOTT. Note that our team currently leads one of the seven VLTI expertise centers in Europe (see page of the Belgian expertise center here).