The MODIS satellite records images of the earth’s surface at 250-m resolution every 16 days. The imagery is very useful for inferring vegetation growth and biomass.
There are a number of ways to download the imagery. However, the web interfaces to download the data are difficult to use, and all of the scripts I’ve found online seem to be outdated (relying on a now defunct ftp server?).
Here is a quick script I wrote to download MODIS NDVI surfaces. It’s written to download 2013 data files that cover California, but it could easily be altered for different time periods and geographic domains.