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Keeping nighttime lighting under control

Yosemite National Park offers stunning views of mountain vistas during the day and star-filled skies at night. This view often includes the Milky Way -- invisible to almost one third of Earth’s population due to light pollution.

Artificial lighting is restricted in Yosemite, but some areas in the park require lighting, such as parking lots and pathways between buildings. Light pollution can not only have a negative effect on visitors’ experiences, but can also change the natural rhythms of the park’s wildlife.

University of California, Merced (UC Merced) graduate student Melissa Ricketts has found a solution – by turning one of her professor’s inventions upside down. In an article from UC Merced’s University News, Ricketts describes what she calls “prescribed irradiance distribution.”

Ricketts is a member of UC Solar, a multicampus research institute headquartered at UC Merced headed by Roland Winston, the inventor of nonimaging optics. His compound parabolic concentrator (CPC) is a key piece of solar-collecting equipment in the emerging solar energy industry. Ricketts has developed a way to make Winston’s CPC emit light rather than gather it.

“It’s the reverse of the solar collector,” Ricketts said. “We can make a perfect square of LED light, or a circle, or whatever shape works best to illuminate only what needs to be illuminated.


Ricketts has been working with Steve Shackelton, a UC Merced staff member and former Yosemite chief ranger, on what they call “The Sand Pile Project.” Although most of their work is done in the lab, designs are occasionally tested in Yosemite on a large pile of sand that snowplow operators spread on the park roads when needed. The park needs to keep the sand pile well-lit so it can be accessed at any time, but lighting should have minimum effects on the surrounding areas.

UC Merced graduate student Melissa Ricketts sets up her LED
 lighting solution in the Sand Pile at Yosemite National Park
Credit: Courtesy of UC Merced

Yosemite is cautious about introducing new technology into the park, but they have been supportive of Ricketts’ research toward managing light by letting her use the area as a test where her work could eventually have global implications for wildlife and park visitors.

“We’re hoping to show the park we can eliminate the unnecessary light,” Ricketts said. She’s currently seeking funding to make the project viable for Yosemite and other parks

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