High-precision calibration of spectrographs using laser frequency combs

We present the first stringent tests of a novel calibration system based on a laser frequency comb (LFC) for radial velocity measurements. The tests were obtained with the high resolution, optical HARPS spectrograph. Photon noise limited repeatability of 9 cm s-1 was obtained, using only little more than one of 72 echelle orders. In the calibration curve CCD inhomogeneities showed up and could be calibrated, which were undetectable with previous Th-Ar calibrations. To obtain an even higher repeatability and lower residuals, a larger spectral bandwidth is necessary. An improved version of the LFC is currently under development. The results of the latest tests will be presented.

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