Collaborative Research: Advanced Wavefront Sensing and Control for Exoplanet Imaging at W.M. Keck Observatory

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Taking pictures of planets around other stars is difficult, because stars are much brighter than planets. However, images of other planets can also tell us what the planet is made of, what its weather might be like, how it formed, and whether it might be home to life. So far, astronomers have only managed to image a handful of planets outside the Solar System, and these planets are unusually hot, bright, and far from their suns. To take pictures of Earth-like planets (which are faint and very close to their suns) astronomers must overcome issues like the turbulence in Earth’s atmosphere and imperfections in the telescope optics. This project will tackle both these issues. A new predictive control method will be investigated that both anticipates the upcoming turbulence, and develops methods to measure and correct the internal optical errors of telescopes. The project’s investigators are involved in teaching and mentoring at the new “AstroTech” summer school. Students from underrepresented and underserved populations in Hawaii will be directly involved in this research through Akamai Workforce Initiative internships and through the University of Hawaii at Hilo. These new approaches will be demonstrated at the Keck Observatory.The last three decades have been marked by the discovery of over 4000 exoplanets orbiting nearby stars. Direct imaging is the preferred method for obtaining high signal-to-noise, high-resolution spectra of diverse exoplanet atmospheres. The performance of modern high contrast imaging systems is limited by the ability to sense and correct the lowest order wavefront aberrations that give rise to contaminating starlight close to the telescope’s diffraction limit. This project will implement two technologies at Keck Observatory to improve spatial resolution. Firstly, predictive wavefront control will minimize the effect of time lag between wavefront sensing and control that results in quickly- evolving speckles at low spatial frequencies. Secondly, focal plane wavefront control that minimizes instrument aberrations that are poorly sensed by the existing adaptive optics systems that give rise to wavefront “speckle” errors.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.