The Tierras Observatory: An ultra-precise photometer to characterize nearby terrestrial exoplanets

TL;DR

The Tierras Observatory is a highly precise, automated photometer designed to detect and characterize terrestrial exoplanets around small stars by minimizing systematic errors and optimizing observational techniques.

Contribution

It introduces a refurbished 1.3-m telescope with specialized optics and filters to achieve unprecedented photometric precision for ground-based exoplanet studies.

Findings

Designed to limit systematic errors to 250 ppm

Optimized for detecting transits of small, nearby stars

Utilizes a narrow bandpass filter to reduce water vapor effects

Abstract

We report on the status of the Tierras Observatory, a refurbished 1.3-m ultra-precise fully-automated photometer located at the F. L. Whipple Observatory atop Mt. Hopkins, Arizona. Tierras is designed to limit systematic errors, notably precipitable water vapor (PWV), to 250 ppm, enabling the characterization of terrestrial planet transits orbiting $< 0.3 \, R_{\odot}$ stars, as well as the potential discovery of exo-moons and exo-rings. The design choices that will enable our science goals include: a four-lens focal reducer and field-flattener to increase the field-of-view of the telescope from a $11.94'$ to a $0.48^{\circ}$ side; a custom narrow bandpass ($40.2$ nm FWHM) filter centered around $863.5$ nm to minimize PWV errors known to limit ground-based photometry of red dwarfs; and a deep-depletion $4K \times 4K$ CCD with a 300ke-full well and QE$>85\%$ in our bandpass, operating in frame transfer mode. We are also pursuing the design of a set of baffles to minimize the significant amount of scattered light reaching the image plane. Tierras will begin science operations in early 2021.