Commissioning and performance results of the WFIRST/PISCES integral field spectrograph

Abstract

Direct imaging of exoplanets has become a priority in the field of exoplanet discovery and characterization due to its ability to directly obtain evidence about a planet’s atmosphere and some bulk properties. Features such as atmospheric composition, structure and clouds are just some of the planetary properties obtainable from directly imaged spectra. However, detecting and observing spectra of exoplanets using direct imaging is challenging due to the combination of extreme star to planet contrast ratios and the relatively small apparent physical separation between a host star and an orbiting planet. Detection of Earth-sized planets in reflected visible light requires contrast ratios of 10^(10), while even detection of Jupiter-sized planets and large young self-luminous planets requires contrast ratios of 10^8 and 10^6, respectively. Consequently, direct detection of exoplanets requires observing strategies which push the boundaries of high contrast imaging. The use of coronagraphy to occult a host star has been combined with adaptive optics (AO) technology to yield a particularly promising means of potentially achieving the required contrast ratios in regions close-in enough to the host star. Ground based adaptive optics systems such as The Gemini Planet Imager (GPI) and Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument have been able to achieve contrast ratios nearing 10^7 using post-processing techniques and have yielded a number of direct detections of young self-luminous planets. Advancing these technologies onto a space based platform immune to the difficulties posed by the effects of Earth’s atmosphere is the next step in accessing even larger contrast ratios.