Procedure Notes: How to Do Stuff
Collage is an NCSA freeware program used to display HDF data. It does not allow you to do anything with the HDF data other than display it (as far as I know). You can use it to see what the values are in your scientific data set, for example, or to display a scientific data set (a scientific data set (SDS) is an official HDF 'object', and is probably the typical data type you will encounter in working with imagery in HDF format).
This note assumes you have a SSM/I brightness temperature HDF file in your possession (e.g., f10_Tb_96035_04A.hdf).
Start collage: path/collage.sn4. Go to File, then Open the hdf file of interest. Hit OK.
The X HDF Browser widget will appear. The left column (probably) should be Groups (but hey, experiment...). The Numeric Data Groups 4-11 contain the 7 channels of SSM/I data (sequence: 19v, 19h, 22v, 37v, 37h, 85v, 85h). Double click on the Numeric Data Group of interest (e.g., NDG=10 for 85v).
The Data Display widget will appear. The large integer values displayed are Tb*100 (i.e., 19215=192.15 K). Go to File, then Make Image. Make Image produces an image of the entire SSM/I swath .
Ok, now you have displayed an HDF image using Collage.