The Tierras Observatory: Ultra-Precise Photometry for Characterizing Exoplanets and Their Host Stars

by Keith CowingNovember 11, 2026November 11, 2026

Graphical overview of the Tierras instrument and its installation. Left: CAD cross-section of the full Tierras instrument installed on the 1.3-m telescope. From top to bottom, the telescope’s native f /13.5 beam (not shown) crosses the primary mirror hole (white), passes through the Tierras filter (pink) and lenses 1–4 (purple), producing an f /5.6 beam. The beam is imaged at the CCD chip (yellow), which is housed in a vacuum chamber inside the dewar (black). Components of the 1.3-m telescope are shown with reduced opacity, whereas opto-mechanical components of our instrument are shown in white. The instrument interface plate is shown in silver. Top right: The focal reducer and field flattener fully integrated with the CCD dewar, resting atop our custom installation cradle and positioned underneath the primary mirror of the telescope (not visible in this view), immediately prior to installation. Bottom right: The Tierras instrument following installation on the 1.3-m telescope. Only the bottom of the CCD dewar is visible from this vantage point, as the rest of the instrument is nested immediately underneath the primary mirror.-- [astro-ph.EP]

[astro-ph.EP] The Tierras Observatory is a fully robotic 1.3-m telescope at the Fred Lawrence Whipple Observatory in southern Arizona.

Tierras achieves sub-part-per-thousand (ppt) photometric precision on two timescales: intra-night, to detect and characterize transits of planets around nearby mid-to-late M dwarfs, and night-to-night across an observing season, to characterize the long-term variability of their host stars.

We describe the facility and instrument design, our photometric pipeline, and our on-sky performance. We present the first ground-based light curves with sub-ppt precision over timescales of months.

This precision enables a range of exoplanet-related science, including the measurement of host star rotation periods, the detection of long-period transits, and the discovery of additional terrestrial planets in known M dwarf systems.

Juliana García-Mejía, Patrick Tamburo, David Charbonneau, Daniel Fabricant, Jonathan M. Irwin, Robert Fata, Joseph M. Zajac, Peter E. Doherty, Brian McLeod, Pascal Fortin, Michael L. Calkins, Gilbert A. Esquerdo

Comments: 27 pages, 15 figures, 3 tables. Submitted to PASP
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2611.12849 [astro-ph.EP] (or arXiv:2611.12849v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2611.12849
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Submission history
From: Juliana García-Mejía
[v1] Mon, 9 Nov 2026 18:41:56 UTC (28,925 KB)
https://arxiv.org/abs/2611.12849

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp... More by Keith Cowing

The Tierras Observatory: Ultra-Precise Photometry for Characterizing Exoplanets and Their Host Stars

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