The Koyal Group Info Mag News\u2502 This Summer, NASA Will

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When you\u2019re working in the yard this summer, take a look up: Using a satellite, NASA scientists are paying attention to how healthy your lawn and garden are.

Next month, the agency plans to launch the Orbiting Carbon Observatory-2. Its primary aim is to create a global map of carbon sources and carbon sinks. The OCO-2 mission will provide the most detailed map of photosynthetic fluorescence \u2014 that is to say, of how plants glow \u2014 ever created. Using this data, scientists should be able to estimate how quickly the world\u2019s plants are absorbing carbon from the atmosphere.

The applications of the project are wide-ranging, but the science is easy enough to understand.

During photosynthesis, a plant absorbs light, then immediately re-emits it at a different wavelength. This is known as fluorescence. In a laboratory setting, botanists can measure the intensity of fluorescence to estimate how actively a plant is photosynthesizing. A satellite could, in theory, detect the light emitted by the world\u2019s plants to estimate how much carbon the plants are absorbing. But there has always been a big, fiery problem: the sun.

The sun is, in most ways, a nice thing to have around. It makes life possible by supplying energy to our planet. From an observational standpoint, though, it can be a major pain. There are huge swaths of the universe that we simply cannot see because the brightness of the sun obscures our view.

In much the same way, the sun was thought to make it impossible to measure global photosynthetic fluorescence. The signals we want to observe are subtle and represent a narrow slice of the electromagnetic spectrum. The sun\u2019s broad-spectrum rays were presumed to overwhelm the wavelengths of plant fluorescence, making them virtually impossible to detect.

That\u2019s where NASA\u2019s Joanna Joiner of the Goddard Space Flight Center in Greenbelt, Md., and Christian Frankenberg of the Jet Propulsion Laboratory in Pasadena, Calif., came in, with their innovative use of an electromagnetic phenomenon known as Fraunhofer lines. In the early 19th century, German optician Joseph Fraunhofer noticed that, in between the beautiful bands of colored light that emerged from a prism, several dark lines appeared. That\u2019s because, by the time sunlight reaches Earth, molecules in the atmosphere have absorbed certain wavelengths of light. In other words, our atmosphere blocks out the sun in certain wavelength bands of the electromagnetic spectrum.

Joiner and Frankenberg realized that they could look for plant fluorescence in the bands of the electromagnetic spectrum where the sun\u2019s light has been dimmed. Data from the Japanese Greenhouse Gases Observing Satellite, which was launched in 2009, confirmed their hunch. Although the OCO-2 project was already in motion by the time Joiner and Frankenberg made their breakthrough,

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