They do this by comparing how long it takes signals from different satellites to reach them. (sciencenewsforstudents.org)
However, the researchers also discover that different satellite data can reveal environmental stresses that crops experience related to drought and heat. (sciencedaily.com)
In fact, there are now well over 150 individual assessments of ice sheet mass balance based on measurements acquired by at least 15 different satellite missions. (imbie.org)