Fiber injection unit

Coupling a high-resolution spectrograph with a high-contrast imaging instrument is the next big step in the direct characterization of exoplanet atmospheres. In this scheme, the high-contrast imaging system serves as a spatial filter to separate the light from the star and the planet, and the high-resolution spectrograph serves as spectral filter, which differentiates between features in the stellar and planetary spectra, e.g., between different absorption lines and radial velocities. High-resolution spectroscopy has three game-changing benefits:

1. Detailed species-by-species molecular characterization (spectral retrieval).

2. Doppler measurements (planet spin, orbital velocity, plus mapping of atmospheric and/or surface features).

3. Last but not least, improved detection capability by side-stepping speckle noise calibration issues affecting low-resolution spectroscopic data from current integral field spectrographs such as SPHERE and GPI.

Most direct imaging results so far have indeed focused on photometry and very low-resolution spectroscopy, due to the lack of instruments designed to optimally merge high contrast imaging (wavefront control and coron- agraphy) and high-resolution spectroscopy at small angles from the host star. KPIC, and its fiber injection unit (FIU) linking Keck AO to NIRSPEC  would enable routine high-resolution characterization of directly imaged low-mass companions and exoplanets. 

© Dimitri Mawet 2017