Abstract

We have developed a sensitive, novel laser heterodyne radiometer using a fiber-coupled distributed feedback laser as the local oscillator to measure Fe(I) Fraunhofer lines Doppler-shifted by the rotational motion of the Sun. The radiometer repetitively measures the Doppler shift of an Fe(I) Fraunhofer line at a vacuum wavelength of 1559.252 nm induced by the Sun’s rotation on its eastern and western limbs. The measured shift is slightly smaller than expected as a result of the simple solar tracking system and collection optics used for demonstration. We show through calculation that a multichannel instrument of identical design in conjunction with a Keck-class telescope can be used to search for exoplanets in nearby star systems using the star-wobble radial velocity method with $1 - \frac{{\rm meter}}{{\rm sec}}$ velocity resolution.

© 2020 Optical Society of America

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