Which Envisat product used for creation of interferogram

I am working in creating a time series using Sentinel 1 SLC IW product but I needed older dates than 2014 so I found out I can combine the results of Envisat InSAR processing but there are many products of this satellite and I need to know which one of these products provided in the link below is used for such purpose. I am looking forward for your aid.

IMS is the standard stripmap product with complex radar informtion

ASA = Envisat

If you search through the IMS collections within that portal you will find the Pair/Interferometric search

that can help you identify suitable pairs of ASAR data to do InSAR…