Reading Themis labels
You need to download the .img file (linked on the image website). This has a header with image details. I use NASAview - a PC program to open the .img files and read the headers. it also has useful but simple image processing to stretch the contrast as required.
In principle, any program that can read binary headers will cope, the trick is knowing the format. You need to dig into the Themis site and the PDS to find data record specifications.