Optical fibers for precise radial velocities: an update

摘要

For the PRV instrument using simultaneous calibration technique such as with sources like thorium lamps, Fabry PerotEtalons or laser comb, it is essential that the instrument stays stable between the wavelength calibration frame and theactual scientific measurement. These instruments are usually in pressure and temperature controlled environments forexample under vacuum. However this is not sufficient to reach the instrumental stability required to get to precision levelof the mssup-1/sup and below required to build the next generation PRV instruments. Another requirement is an as constant aspossible illumination of the spectrograph to stabilize the line profile of the instrument. To achieve this, it is necessary to usea device that will scramble the light coming from the star to mitigate the effects of the atmosphere. In addition this deviceshould not increase significantly the beam etendue, which is already a technological challenge for large telescopes. Thecommon solution to this problem is to use optical fibers. Historically the solution has been to use circular fibers as theywere the only one available. Recently for other purposes non-circular fibers have been developed and made available. Theyhave been tested, and present an important improvement in the scrambling over the circular fibers. We will present inthis paper the properties of the octagonal fibers used for the HARPS-N2 instrument and the achieved performance of itsfiber train.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.