Keck II Telescope Receives Upgrade to See in Infrared

The newly upgraded adaptive optics (AO) system on W.M. Keck Observatory’s Keck II telescope now features the first infrared pyramid wavefront sensor available for scientific use.

AO is a technique used to remove the blurring of astronomical images caused by turbulence in the Earth’s atmosphere. The paper detailing the project was published in the Journal of Astronomical Telescopes, Instruments, and Systems.

With the new infrared pyramid wavefront sensor, Keck II’s AO system can better detect cooler, hard-to-see objects in the universe such as exoplanets, protoplanets, and young dwarf stars.

Most observatories use visible-wavelength Shack-Hartmann or pyramid wavefront sensors, said Peter Wizinowich, chief of technical development at Keck Observatory and principal investigator for this project.

“It’s like adding night-vision goggles to Keck’s AO system,” said lead author Charlotte Bond, a postdoctoral AO scientist who led the project development team. “The infrared pyramid wavefront sensor is especially desirable for the study of baby exoplanets, which are expected to orbit cooler, redder stars or be shrouded in dust, making them faint at visible wavelengths but relatively bright in the infrared.”

The University of Hawaiʻi Institute for Astronomy provided the camera for the pyramid wavefront sensor, which is based on a new technology, very low noise, infrared avalanche photodiode array.

The Keck II telescope’s AO upgrade also involves a new GPU-based real-time controller (RTC) that analyzes the image coming from the pyramid wavefront sensor then controls the deformable mirror to correct the atmospheric distortions. The software architecture implemented on the RTC is based on code developed by Olivier Guyon at Subaru Telescope.

“This has been one of the most exciting projects I’ve ever worked on,” said co-author Sylvain Cetre, a software engineer at Keck Observatory and one of the lead project developers. “The new RTC performs heavy computations in the shortest time possible at very high speeds, resulting in a dramatic improvement in image quality.