Imaging sensors for PoET: a spatially resolved solar spectroscopy instrument

Abstract

The study of the Sun is an area still open in several topics of astrophysics, in a field that has seen an expansion in recent years - therefore, it is critical that collected data is thoroughly traceable and accurate to be used in new study cases or predictive models. A ground based, portable, optimized system, consisting of a Schmidt-Cassegrain telescope coupled to a refractor telescope acting as a pointing telescope, is being designed to provide high resolution imaging of smaller areas on the Sun’s surface, being able to obtain disk-resolved, high spectral resolution data, at a relative low cost (compared to large consortium developed instruments). The light collected by the telescope will be fibre-fed to a spectrograph - the injection of light in the fibre is critical and requires an imaging sensor to aid the light guiding process. The goal of the present work was to explore the best candidates for the image sensors, their architectures, requirements, and constraints, as well as their expected performance range and signal noise. The trade-off analysis between CMOS and CCD based sensors was made and it was concluded, that for the intended application, either type of architecture is admissible, provided the sensor is within desired parameters.

Solar photospheric spectrum microvariability

“…Of additional interest is data from across a spatially slightly resolved solar disk, measured with comparable precision, for example monitoring the characteristics in wavelength jittering in quiet areas versus magnetic ones. This behavior can be theoretically predicted, but the corresponding observations are not yet available, although projects are in progress (Leite et al 2022).…”

“…For measurements of integrated sunlight, the amplitudes from the simulation area have to be reduced by a large factor, but only by a small amount (if any) in spatially resolved data. These observations should become practical with forthcoming solar telescopes, where light from sections of a spatially somewhat resolved solar image is fed into a high-precision instrument, for example the PoET project at the ESPRESSO spectrometer of ESO in Chile (Leite et al 2022).…”

The Extreme Stellar-signals Project. III. Combining Solar Data from HARPS, HARPS-N, EXPRES, and NEID

“…In this analysis, EXPRES and NEID are in the same time zone and share by far the greatest number of overlapping data points. It will soon be possible to perform a similar analysis with HARPS and HARPS-N data as solar telescopes for ESPRESSO (PoET; Leite et al 2022) 38 and HARPS-3 (ABORAS;Farret Jentink et al 2022) come online, covering the same time range as HARPS and HARPS-N, respectively.…”

“…PEPSI (Strassmeier et al 2015) and GIANO-B (Claudi et al 2018) also have solar feeds. Solar feeds for KPF (R. Rubenzahl 2023, in preparation), ESPRESSO (Leite et al 2022), HARPS-3 (Farret Jentink et al 2022), MAROON-X (Seifahrt et al 2018), andNIRPS (Bouchy et al 2017) are in the works. We note that shorter exposure times give rise to less error when binned to share time stamps, meaning shorter solar exposures will be easier to compare with observations from other instruments.…”

“…Several planet-hunting spectrographs therefore have solar feeds-i.e., the High-Accuracy Radial-velocity Planet Searcher (HARPS), the High-Accuracy Radial-velocity Planet Searcher in the North (HARPS-N; Phillips et al 2016), the EXtreme PREcision SPectrograph (EXPRES; J. Llama 2023, in preparation), the NN-explore Exoplanet Investigations with Doppler spectroscopy instrument (NEID; Lin et al 2022), and the Keck Planet Finder (KPF; R. Rubenzahl 2023, in preparation). Other instruments have plans to add a solar feed-e.g., on the Échelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO; Leite et al 2022) or the M dwarf Advanced Radial velocity Observer Of Neighboring eXoplanets (MAROON-X).…”