Ifg problems with ERS and ENVISAT

I am currently working on the last project of my degree in Geomatics at the University of Jaén (Spain). This addresses the way to quantify the ground deformation caused by earthquakes.

I am using SNAP software to analyse some images of ERS, ENVISAT and ALOS in order to compare the results from L’Aquila earthquake happened on 6/April/2009.

For ENVISAT, I’m using this images:


And for ERS:


I’m following the sames steps like sentinel process, but i dont obtain any results in the interferogram.

  1. Apply Orbits
  2. Subset and Multillok.
  3. Coregistration.
  4. ifg.
    am I forgotten some step? i got the same problem for ERS…

I would really appreciate yours answers.