NASA’s data is free to the public, and there are a number of different ways to get it. Different interfaces will allow you to subset the data in different ways or even interactively view the data you’d like to download. You’ll need to register with NASA, regardless of which interface you choose to use, but registration is quick, easy, and, again, free. We’ve put together a how-to to get you downloading as quickly as possible.
Find the on-line how-to here.
You can also download the pdf version here.