Advice on SARMosaic operator

Dear colleagues,
I’m stuck with the following:

  1. the task is to produce interferogram over area covered by the subsequent and slightly overlapping scenes for an earthquake event
  2. first I tried to process the sub-swats from two SAR sets separately , but the result was really poor
  3. Next I decided to extract only the bursts from the two sub-swats from the that cover the area of interest from the 4 SAR scenes, process them with orbital information and merge them with SAR Mosaic. My idea was to produce interferogram from the merged bursts starting with BackGeocoding. It was a surprise that SAR Mosaic works with Geocoded products.
    The question is - why the information in the original SAR data is not enough for this operation? Is it not sufficient to to make this operation.

Thank you for your comments.