NRC's adaptive optics help astronomers see better and farther into space

- Victoria, British Columbia,

Twinkling stars have enchanted humans since the dawn of time. But they make it hard for astronomers to get clear images of the skies. Great news: advanced technology developed by the National Research Council of Canada (NRC) takes the twinkle out, and changes the game for studying our universe.

Once the light from a star enters the earth's atmosphere, it passes through several layers of air turbulence that appear to make the light flicker or twinkle. This effect also distorts images taken by telescopes on the ground. Fortunately, scientists can now remove that atmospheric disturbance with adaptive optics, clearing the air for those telescopes to take crisp, pure images.

Researchers at the NRC's Herzberg Astronomy and Astrophysics Research Centre have developed an experimental adaptive optics system that is undergoing rigorous tests on their 1.2-metre McKellar Telescope in British Columbia. This project—Research, Experiment and Validation of Adaptive Optics with a Legacy Telescope (REVOLT)—uses advanced cameras, high-speed computers and bendable mirrors to correct the effects of atmospheric turbulence. With adaptive optics, the images produced by telescopes on earth can be as high-quality and high-resolution as they would be from telescopes in space above the atmosphere, and cost much less.

According to Dr. Jean-Pierre Véran, Adaptive Optics team leader at the Herzberg Astronomy and Astrophysics Research Centre, REVOLT has immense implications for larger optical telescopes now in place (up to 10 metres) and in development (up to 39 metres). "Time on these big telescopes around the world is in very high demand, so when they acquire new technology, they want proof that it has a very high level of maturity," he says. "REVOLT serves as a test bench that allows us to validate new technologies on a small telescope in operational conditions."

Image of the star Alpha Persei with the system off (left) and on (right) shows REVOLT improved the resolution by a factor of 5 and the sensitivity by a factor of almost 500.

He points out that the project, which took about 2 years to complete, was successfully tested on the McKellar Telescope for the first time in August 2022, with more observations planned for September. "This means we can see an object almost 500 times fainter with the same amount of observing time, which is an illustration of one of the key benefits of Adaptive Optics for large research telescopes," says Dr. Kathryn Jackson, Adaptive Optics scientist at the Herzberg Astronomy and Astrophysics Research Centre. The research showed that REVOLT was able to efficiently correct the atmospheric turbulence, demonstrating that 2 novel technologies performed as expected when tested in operational conditions. These are the Herzberg Extensible Adaptive Real-Time Toolkit (HEART) and a new commercial high-speed camera called C-Blue One.

Real-time control platform and camera

HEART's first client, the Gemini North Observatory in Hawaii, tasked the researchers to work with the Gemini North Adaptive Optics (GNAO) imager to fix the twinkle for the observatory's massive telescope.

The instrument's real-time controller (RTC) is based on HEART, created by the research centre's multidisciplinary team. HEART's layout, architecture and tools make it easy to adapt to and drive any adaptive optics system. The GNAO RTC acts as the brain of the system, which processes incoming natural and laser-guide star sensor signals and issues commands to the deformable mirrors.

"This system will be able to capture astronomical images with unprecedented resolution, sensitivity and contrast," says Jennifer Dunn, head of the research centre's Software Group. "Once installed, it will significantly increase the scientific productivity of Gemini." HEART will also be deployed on several adaptive optics systems in observatories around the world.

An integral part of the platform is the new commercial C-Blue One camera by First Light Imaging. The REVOLT experiment was the first time this camera was used in an AO system on a telescope observing real astronomical objects. In REVOLT, this CMOS low-noise digital camera takes 1000 high-resolution images per second.

Putting it all together

The multidisciplinary REVOLT team includes engineers and scientists specializing in adaptive optics, software, high-precision opto-mechanics and electronics. They will also be working with other NRC research centres that will use the test bed starting this fall.

For example, the REVOLT system will be used to feed corrected starlight into an optical fibre, to enable an on-sky demonstration of a novel fibre-fed prototype instrument known as a spectral correlation sensor. This sensor, which was jointly developed by researchers at the Herzberg Astronomy and Astrophysics and Advanced Electronics and Photonics research centres, exploits the advantages of silicon photonics chip technology to produce an ultra-compact, lightweight astronomical instrument that will be used for high-sensitivity, real-time, remote gas detection in stellar and planetary atmospheres. This will be the first field test of this new instrument technology, using real operating conditions at a professional grade telescope.

Furthermore, the NRC's Nanotechnology Research Centre will test-drive a new generation of low-voltage deformable mirrors (LVDM) on REVOLT. LVDM can correct distorted images from land-based telescopes and ground-to-space communications waves due to turbulence in the atmosphere. LVDM is key to integrate various components of a Micro-Electro-Mechanical System Deformable Mirror, including the mirror face sheet, the electromagnetic actuator, the circuits on a semiconductor wafer and the printed circuit board, all because of low driving voltage utilized by the electromagnetic force (known as the Lorentz force) from a powerful permanent magnet. LVDM is helping to compensate for atmospheric turbulence in real time with incredibly low power consumption, high mirror displacement, high fill factor of the reflective deformable mirror surface, and with a 1 millisecond response time.

REVOLT is instrumental in demonstrating novel technologies that are critical to the advancement of adaptive optics, which is key to progress in astronomy and physics, and in our understanding of how nature works. Adaptive optics also enables disruptive technologies used in many fields, including telecommunications, ophthalmology, microscopy and laser treatment of diseases.

"It has many long-term benefits for Canadians and other citizens of the world, and the faster we are able to develop these new technologies, the sooner we can effect important changes," concludes Dr. Véran.

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