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Award Winning Algorithm Takes Subaru's Search for Habitable Planets to the Next Level

October 17, 2018

An international team of scientists, including astronomers from the Subaru Telescope and the Paris Observatory, high performance computing experts from the King Abdullah University for Science and Technology (KAUST), in collaboration with hardware giant NVIDIA, is taking the search for habitable planets and observation of the first epoch galaxies to the next level.

On-sky demonstration was recently achieved with the Subaru Chronographic Extreme Adaptive Optics (SCExAO) mounted on the Subaru Telescope. A team at the Paris Observatory is already scaling up the algorithms for future larger telescopes. KAUST's Extreme Computing Research Center (ECRC) is working with the astronomers to develop the advanced Extreme-AO algorithms that will meet the formidable habitable exoplanet imaging challenge.


Figure 1

Figure: Scientists working with SCExAO, mounted at the Nasmyth Infrared platform of the Subaru Telescope. (Credit: NAOJ)



"Imaging exoplanets with large ground based telescopes is very challenging due to the star/planet contrast and blurring induced by Earth's atmosphere. Very high performance adaptive optics (AO), sometimes referred to as 'Extreme-AO', are required," says Dr. Hatem Ltaief, Senior Research Scientist in the Extreme Computing Research Center at KAUST.

A radically new approach to Adaptive Optics has emerged from this collaboration: faster, bigger, and much smarter control algorithms. Powered by KAUST's linear algebra code running on NVIDIA's graphical processing units (GPUs), the new computational system continuously optimizes itself, and even learns to anticipate fast-changing optical disturbances induced by Earth's atmosphere.

"This fantastic new technology is already being used to take a closer look at exoplanets orbiting around nearby stars. With the larger 25-40 m telescopes astronomers are currently building, new Earth-like planets orbiting nearby stars will be imaged and their atmospheric composition will be measured to look for signs of life such as, Oxygen, Water or Methane," says Professor Damien Gratadour at the Paris Observatory.

ECRC researchers at KAUST recently implemented a new Singular Value Decomposition (SVD) algorithm, often referred as the workhorse for numerical linear algebra, to optimally control a small high-speed deformable mirror to compensate for atmospheric turbulence. This research resulted in one of the best paper awards at the Platform for Advanced Scientific Computing (PASC) Conference 2018 in Basel, Switzerland. The innovation is already successfully used by astronomers to image exoplanets with the 8.2 m diameter Subaru Telescope.

"This challenge is further exacerbated with large telescopes, where imaging habitable planets through Earth's atmosphere is notoriously difficult, and requires a new approach to adaptive optics. Our previous AO systems were quite slow and lagging behind the fast-changing optical aberration due to atmospheric turbulence. The SVD algorithm developed by KAUST scientists is enabling us to correct in real-time for atmospheric blurring of images taken by large telescopes using smarter Extreme-AO. The algorithm now learns to optimize itself, and we are no longer outsmarted by turbulence," says SCExAO project scientist Dr. Oliver Guyon at the Subaru Telescope.

Working closely with NVIDIA has been critical to the success of the project, "This is an unprecedented high performance computing (HPC) challenge. Optical aberrations induced by atmosphere change over millisecond timescale, and on current large telescopes, algorithm must compute 1000s of deformable actuators positions in a millisecond or less to sharpen images. The Subaru Telescope is the highest recorded terrestrial use of these kind of GPU systems. We are continuing to work with the team as the hardware is scaled up for this exciting project due to the critical performance impact of NVIDIA GPUs," says Steve Oberlin, Chief Technology Officer at NVIDIA.

The work of the project team adds to the historic contribution of the Middle East into the field of astronomy. "We are helping astronomers make better use of today and tomorrow's most advanced telescopes. Interestingly many of the stars we are observing with the Subaru Telescope were first catalogued by stargazers in the region and have retained their Arabic names. We hope to contribute to the tradition of astronomy in the region," notes Dr. Ltaief. KAUST's high performance computing (HPC) solutions are also becoming a critical part in the design of future instruments aimed at imaging the most distant galaxies. Moving forward, ECRC researchers together with Paris Observatory and Subaru Telescope's astronomers are currently defining a common roadmap for sustainable software development.




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