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Exoplanets can be detected from a time series of stellar spectra by looking for small, periodic shifts in the absorption
features that are consistent with Doppler shifts caused by the presence of an exoplanet, or multiple exoplanets, in the
system. While hundreds of large exoplanets have already been discovered with the Doppler technique (also called radial
velocity), our goal is to improve the measurement precision so that many Earth-like planets can be detected. The smaller
mass and longer period of true Earth analogues require the ability to detect a reflex velocity of ~10 cm/s over long time
periods. Currently, typical astronomical spectrographs calibrate using either Iodine absorptive cells or Thorium Argon
lamps and achieve ~10 m/s precision, with the most stable spectrographs pushing down to ~2 m/s. High velocity
precision is currently achieved at HARPS by controlling the thermal and pressure environment of the spectrograph.
These environmental controls increase the cost of the spectrograph, and it is not feasible to simply retrofit existing
spectrometers. We propose a fiber-fed high precision spectrograph design that combines the existing ~5000-6000 A
Iodine calibration system with a high-precision Laser Frequency Comb (LFC) system from ~6000-7000 A that just
meets the redward side of the Iodine lines. The scientific motivation for such a system includes: a 1000 A span in the red
is currently achievable with LFC systems, combining the two calibration methods increases the wavelength range by a
factor of two, and moving redward decreases the "noise" from starspots. The proposed LFC system design employs a
fiber laser, tunable serial Fabry-Perot cavity filters to match the resolution of the LFC system to that of standard
astronomical spectrographs, and terminal ultrasonic vibration of the multimode fiber for a stable point spread function.
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