The Doppler radial velocity (RV) technique continues to drive our understanding of planet masses, their interior structure, and orbital dynamics. However, technology advances in this field have reached an impasse. Doppler precision has leveled off and progress is impeded by fundamental limitations set by basic physics. Governed by the design decisions of the earliest spectrographs, existing RV instruments are limited to studying planets with RV semi-amplitudes of ~1 meter per second: this makes the difference between detecting gas giant planets and Earth-like worlds orbiting in the habitable zone and has important scientific implications for TESS and JWST.
We are developing a planet-finding spectrograph for the Large Binocular Telescope named “iLocater” that uses “extreme” adaptive optics (AO) to couple starlight directly into single mode fibers, eliminating the effects of modal noise entirely. By correcting for the image-blurring effects introduced by Earth’s turbulent atmosphere, iLocater shows promise to finally overcome the “1 m/s barrier.” In this talk I will describe the many-fold benefits of building an RV spectrograph that operates at the diffraction-limit. In particular, I will argue that AO-fed instruments on large telescopes may represent the only path towards generating 10 cm/s precision. Finally, I will provide an update on the iLocater project, highlighting recent on-sky results for injecting starlight into single mode fibers.
