Lasers, Holography Tested as Weather Forecast Tools

WESTMINSTER, Md. — Most nights, David Guerra climbs a spiral staircase to the roof of the physics building at Western Maryland College and shoots laser beams into the quiet sky.

Based on his experiments, NASA hopes to mount a similar machine on a satellite within five years to fire lasers into Earth’s atmosphere.

The goal: better weather forecasts, with implications for everything from food production to disaster preparation.

The project is part of NASA’s New Millennium program, which aims to expand our understanding of the universe by using smaller, more efficient instruments that are cheaper to launch into space.

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Guerra’s device is a telescope that uses lasers and holography to “see” atmospheric structures. It detects clouds and pollutants, but its real importance is its potential for reading the winds.

Atmospheric winds drive the weather, said Geary Schwemmer, a research engineer at NASA’s Goddard Space Flight Center in Greenbelt, who is overseeing the project.

“If we had a better knowledge of winds, that would give us an improvement in weather forecasting,” he said.

Laser and holographic telescopes could replace the comparatively crude anemometers and weather balloons that now provide wind data, Schwemmer said. The experimental instruments are 1,000 times more sensitive, capable of reading atmospheric layers in meters, not kilometers, he said.

Schwemmer invented the holographic telescope that Guerra and two students are testing under a three-year, $40,000 cooperative agreement with the space agency. It is the world’s only laser telescope with a holographic optical element, Schwemmer said.

“We’re sort of perfecting the technology,” Guerra said.

The telescope has three main components: a laser, a holographic optical element and a detector. It looks like a 7-foot metal tripod standing next to an end table topped by a blue box resembling a computer’s central processing unit. Directly beneath the tripod is the holographic element, a blue-green glass disc the size of a large pizza.

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The laser shoots horizontally out of the box into a mirror that reflects the beam straight down onto the spinning disc. The holographic disc bounces the beam back upward at an angle.

As the concentrated beam of light moves upward, gradually diffusing, it strikes particles in the air that reflect the light in all directions.

Some of the reflected light falls back onto the holographic disc, which then focuses the reflected light onto the detector atop the tripod. The detector transforms the light into electrical impulses that can be used to discern wind speed and direction, as well as cloud boundaries and concentrations of particles in the atmosphere.

A version of the holographic telescope will be tested on a space shuttle flight as early as 2000, and one could be mounted on a satellite within two years after that, Schwemmer said.