Performance Verification of the EXtreme PREcision Spectrograph

Journal
Date Issued
2020
Author(s)
Blackman, Ryan T.
•
Fischer, Debra A.
•
Jurgenson, Colby A.
•
Sawyer, David
•
McCracken, Tyler M.
•
Szymkowiak, Andrew E.
•
Petersburg, Ryan R.
•
Joel Ong, J. M.
•
Brewer, John M.
•
Zhao, Lily L.
•
Leet, Christopher
•
Buchhave, Lars A.
•
Tronsgaard, René
•
Llama, Joe
•
Sawyer, Travis
•
Davis, Allen B.
•
Cabot, Samuel H.C.
•
Shao, Michael
•
Trahan, Russell
•
Nemati, Bijan
•
•
•
•
Fournier, Paul
•
Pawluczyk, Rafal
DOI
Abstract
The EXtreme PREcision Spectrograph (EXPRES) is a new Doppler spectrograph designed to reach a radial-velocity measurement precision sufficient to detect Earth-like exoplanets orbiting nearby, bright stars. We report on extensive laboratory testing and on-sky observations to quantitatively assess the instrumental radial-velocity measurement precision of EXPRES, with a focused discussion of individual terms in the instrument error budget. We find that EXPRES can reach a single-measurement instrument calibration precision better than 10 cm s-1, not including photon noise from stellar observations. We also report on the performance of the various environmental, mechanical, and optical subsystems of EXPRES, assessing any contributions to radial-velocity error. For atmospheric and telescope related effects, this includes the fast tip-tilt guiding system, atmospheric dispersion compensation, and the chromatic exposure meter. For instrument calibration, this includes the laser fRequency comb (LFC), flat-field light source, CCD detector, and effects in the optical fibers. Modal noise is mitigated to a negligible level via a chaotic fiber agitator, which is especially important for wavelength calibration with the LFC. Regarding detector effects, we empirically assess the impact on the radial-velocity precision due to pixel-position nonuniformities and charge transfer inefficiency (CTI). EXPRES has begun its science survey to discover exoplanets orbiting G-dwarf and K-dwarf stars, in addition to transit spectroscopy and measurements of the Rossiter-McLaughlin effect.
Volume
159
Issue
5
Start page
238
Uri
Url
Issn Identifier
0004-6256
Rights
open.access
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