EXPRES: A Next-Generation Spectrograph

EXPRES (the Extreme PREcision Spectrograph) is a R~137,000, fiber-fed, optical spectrograph installed at the 4.3-m Lowell Discovery Telescope near Flagstaff, Arizona. I will give an overview of the optical design, commissioning, and software development that has gone into EXPRES. The instrument itself has demonstrated a stability of 4-7 cm/s. We have constructed a flat-relative, optimal-extraction based pipeline that returns on-sky, single-measurement precision of ~30 cm/s for observations with per-pixel S/N of 250. I will highlight Excalibur, a novel hierarchical, non-parametric method for wavelength calibration. Recent EXPRES data of known planetary systems show sub-m/s residual RMS. EXPRES data is also being used for a community-wide "EXPRES Stellar Signals Project" to diagnose stellar photospheric velocities.

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