I'm currently trying to retrieve data from http://smap.jpl.nasa.gov/data/ and use it in ArcMap. The issue is that the data is curved towards the poles and so the bottom left of the extent isn't the same latitude as the bottom right. This means that even if I define the projection as WGS 1984, it doesn't look as it should look. It comes up as a rectangular raster that isn't in the right geographic location.
Some things to note... The HDF5 contains a grid of latitude values as well as a grid of longitude values along with the soil moisture subdatasets I'm interested in working with. These are separate subdatasets but maybe I could save them as text files, import them into excel, and then merge them somehow into file readable by ArcMap. This way when combined with the soil moisture data I'll be able to see it in ArcMap in the right geographic location.