$4M NASA grant will help UH researchers develop new sensors for mission to find possibly inhabitable Earth-like exoplanets

University of Hawai‘i Institute for Astronomy astronomer Michael Bottom and his research team are developing the next generation of ultra-sensitive sensors necessary to observe distant Earth-like exoplanets and their atmospheres. Their mission recently got a $4 million boost thanks to a NASA grant.

For the past several years, with NASA support, astronomers at the Institute for Astronomy and industry partners at Leonardo, Markury Scientific and Hawai‘i Aerospace have been maturing the new tech, known as mercury, cadmium and tellurium linear-mode avalanche photodiode arrays, and already demonstrated how it works with 1 Megapixel sensors. Those sensors are small compared to visible-light detectors such as those in modern smartphone cameras, but the NASA grant will enable Bottom and his team to increase the size to 4 Megapixels.

Bottom and his team will provide those cutting-edge sensors for a new 6-meter space telescope optimized for direct imaging and spectroscopy of exoplanets. The new telescope is of the highest priority in the 2022 Decadal Survey on Astronomy and Astrophysics. The survey lays out the top U.S. astronomy priorities for the next decade.

The ambitious new mission aims to unambiguously identify and classify about 25 Earth-like exoplanets to determine if they possess atmospheres suitable for life.

“The technology developments required to make this space mission viable are extremely ambitious, and detectors are among the most difficult parts,” Bottom said in a press release. “But when it flies, we’ll be able to tell for the first time if habitable, Earth-like planets are common in our corner of the universe.”

The mission is extremely challenging because light reflecting from the Earth-like planets is very faint. Taking images of such planets is impossible today, and making detailed measurements of their atmospheres is even harder.

Many ground- and space-based telescopes, including the Hubble Space Telescope, James Webb Space Telescope, Keck Observatory and dozens more, already use infrared sensors developed by the UH astronomy institute, which is one of the world leaders in infrared imaging technologies. Called mercury, cadmium and tellurium astronomical wide area infrared imager — or HAWAII — arrays, they were developed by the late Don Hall along with current team members institute astronomer Klaus Hodapp and engineer Shane Jacobson as well as many others.

Unfortunately, even the best infrared detectors still have too much inherent electronic noise, the graininess in images shot in low-light conditions with a high camera sensor sensitivity setting. Despite decades of development, scientists and engineers have not been able to significantly reduce this electronic noise.

One solution is to multiply the signal received by the detector before measuring it electronically.

“Bottom and his team are on track to overcome this hurdle by applying a high voltage across the detector so that every detection of a light particle, a photon, kicks off an avalanche of electrons that easily overcomes the electronic detector noise,” Hodapp said in the press release.

While the primary goal of developing the tech is to enable the science planned for the upcoming exoplanet identification and classification project, the new detector could also be used by other projects that look at space-based spectroscopy of faint galaxies, precision photometry and ground-based high-resolution infrared spectroscopy.

“This new sensor has been developed over a decade on a number of projects, including a Nobel Prize award-winning program for the exploration of black holes,” Keith Barnes, science detectors program manager at Leonardo, Markury Scientific and Hawai‘i Aerospace, said in the press release. “So we feel excited to see how far our joint capability can help uncover more secrets of the universe.”