NASA instrument scientist Bryan Blair had just finished writing the flight software for the agency’s Mars Orbiter Laser Altimeter, or MOLA, when he was invited in 1991 to fly a lidar instrument aboard a P-3 research aircraft to test new lidar techniques over the ice sheets in Greenland. En route, he gathered measurements of forested areas in New York state. What he discovered in the data stunned him, resulting in a 27-year quest to build a spaceborne lidar for measuring forests.