The Carnegie Planet Finder Spectrograph: integration and commissioning

Abstract

The Carnegie Planet Finder Spectrograph (PFS) has been commissioned for use with the 6.5 meter Magellan Clay telescope at Las Campanas Observatory in Chile. PFS is optimized for high precision measurements of stellar radial velocities to support an ongoing search for extrasolar planets. PFS uses an R4 echelle grating and a prism cross-disperser in a Littrow arrangement to provide complete wavelength coverage between 388 and 668 nm distributed across 64 orders. The spectral resolution is 38,000 with a 1 arcsecond wide slit. An iodine absorption cell is used to superimpose well-defined absorption features on the stellar spectra, providing a fiducial wavelength reference. Several uncommon features have been implemented in the pursuit of increased velocity stability. These include enclosing the echelle grating in a vacuum tank, actively controlling the temperature of the instrument, providing a time delayed integration mode to improve flatfielding, and actively controlling the telescope guiding and focus using an image of the target star on the slit. Data collected in the first five months of scientific operation indicate that velocity precision better than 1 m s -1 RMS is being achieved.