Seeing is the effect of random fluctuations in the index of refraction throughout the Earth’s atmosphere which result in random fluctuations in the direction of light from a distant source. Scintillation is the random fluctuation of the light intensity received. In 1993, a correlation was found between seeing and scintillation. Using this concept, and by using a non-telescopic method, we can measure seeing during the day, using the sun as the source of light. PoET is the Paranal solar Espresso Telescope that will be connected to the ESPRESSO high resolution spectrograph. Using the Sun as a proxy, PoET will allow us to understand the physical processes responsible for the stellar noise in ultra-high precision spectroscopy studies of exoplanets. PoET will be able to point to any region in the solar disk and obtain a high-resolution spectrum, of spatially resolved region, between 1 and 60 arcsec areas in the solar disk. Therefore, it is crucial to understand the atmospheric conditions during the day to be able to define which aperture PoET will be observing with. In this context, we are implementing a solar seeing measurement instrument that will be used to measure the seeing during the day in Paranal, Chile where PoET will be installed. In this paper, we will discuss the concept behind the instrument, and present its current phase. We will present the optomechanical, electronics, and software-related components; as well as the first on-sky testing measurements.
There are currently important challenges imposed by stellar “noise” often associated with the discovery and characterization of exoplanets similar to Earth. In particular, various physical processes occurring on the stellar photosphere modify stellar spectra, severely challenging the detection and characterization of low-mass planets. A detailed study of the Sun can be used as a spectral proxy to a better understanding of the variable noise sources present in solar-type stars. By obtaining full integrations of the solar disk ("sun-as-a-star observations") in combination with high resolution, spatially resolved observations of smaller areas, the acquired spectra will help in the identification of individual stellar features responsible for the observed spectral deformations. The Instituto de Astrofísica e Ciências do Espaço (Portugal) is currently developing an instrument to approach this challenge. In conjunction with the high-resolution spectrograph ESPRESSO (spectral resolutions of R ~140 000 and ~190 000, HR and UHR modes, respectively), the Paranal solar ESPRESSO Telescope (PoET) will have two dedicated telescopes to map the Sun’s surface through disk-resolved and disk-integrated measurements, with respective telescope diameters of 600 and 75 millimeters. PoET has the requirement to perform disk-resolved observations from 1 to 60 arcseconds in conjunction with the full disk. In this work, a summary of the current configuration of the system – PoET’s telescopes and their frontends – will be given, as well as the preliminary assumptions made to build PoET, with consideration for the light requirements of the ESPRESSO spectrograph.
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