NASA's PACE Satellite Maps Fall Color Planetwide
A hyperspectral ocean sensor is now tracking autumn leaf pigments across the entire globe, every day or two.
By The space-quantum Desk
NASA's PACE satellite was designed to study ocean ecosystems, but its hyperspectral OCI instrument—scanning at 286 spectral bands—turns out to be a remarkably precise tool for reading the colors of autumn forests. [1]
PACE is the first satellite capable of measuring all three key leaf pigments—anthocyanins (reds), carotenoids (yellows and oranges), and chlorophylls (greens)—across the entire planet every day or two. [1] By tracking how much red, orange, and yellow forests show compared with green, scientists can pinpoint where leaves are changing and when color peaks in any given region.
The satellite detected particularly high levels of redness in parts of northern and eastern Russia, northern Alaska, and northern Canada from September 29 to October 4. [1] In New England and upstate New York, redness began to fade during the week of October 5 to 11, even as it spread across much of the Midwest and the Mid-Atlantic. [1]
The tradition PACE is now instrumenting has deep roots. The Japanese practice of momijigari—the direct translation of which is "Red leaves hunting"—dates to the Nara period (710–794), with autumn foliage celebrated in Manyoshu, the oldest collection of Japanese waka poems that were compiled during the Nara period. [2] In America, organized leaf-peeping entered the historical record in the 19th century. [1]
What was once a matter of timing, intuition, and geography is now a data stream—one that collapses the distance between a satellite's daily pass and a hillside thick with maples.
NASA data scientist Skye Caplan is posting weekly foliage maps and asking the public to submit ground photos to help "ground truth" PACE observations. [1] The team hopes the data will eventually support research into wildfire risk, the global carbon cycle, and early detection of drought, insect infestations, and plant disease. [1]
As Caplan put it: "Color changes happen kind of slowly, then all at once, and then they're gone." [1] The satellite, at least, never blinks.