Radial Velocity Spectrograph Project
Timeline: goal is to be on sky by 2016
We aim to build a new instrument with the capability to detect Earth-size planets in the habitable zones of mid- to late-M dwarfs using the radial velocity method. The instrument will be a high-resolution, bench-mounted spectrograph capable of delivering 1 m/s radial velocity precision for M dwarfs down to and beyond V = 16. It will be installed at one of the 6.5m Magellan telescopes at Las Campanas Observatory. The capability that this instrument will have is well beyond the reach of any existing instrument. The anticipated uses for the instrument are to (1) conduct a radial velocity only survey for potentially habitable planets around nearby mid- to late-M dwarfs and (2) to confirm and measure the masses of low-mass planet candidates identified in the habitable zones of M dwarfs by ground- and space-based transit surveys. These later objects will be the best objects for future atmospheric studies of potentially habitable planets.
The main constraint for the instrument is set by the desired wavelength coverage. The important wavelength range for the instrument is 700 -- 900 nm because this is the region containing the maximum radial velocity information for mid to late M dwarfs. There is no gas cell useful for this region, so the instrument must be intrinsically stable to deliver the desired radial velocity precision. This means that the optical setup must be fixed and that the entire instrument must be in a vacuum tank and in a temperature stabilized enclosure. The instrument must also be fiber-fed to maintain illumination stability. A resolving power of approximately 85,000 is necessary. A similar setup can not be realized by making straightforward modifications to existing instruments - a new instrument must be built to achieve the radial velocity precision goal for the target stars.
We are currently in the design phase for this instrument. Below is a Zemax drawing of our preliminary optical layout.