This article from IEEE  talks about how satellite data can predict agricultural output and famine.  Terra plays a large role in measuring the National Data Vegetation Index (NDVI), which is measured using spectral bands 1 and 2 (infrared to visible light) of the Moderate-resolution Imaging Spectroradiometer. NDVI compares the amount of light reflected in near-infrared with that reflected in visible light; if there is more infrared, the vegetation in that spot is likely to be dense and thus yield more of the crop.” Armed with this information and data from other satellites researchers are able to get a better picture of how the worlds crops are faring.  Read more