When I was use Sentinel1 data with SAR Simulation in SANP,at first,I do split with s-1 TOPS Split tool,and then I do deburst with s-1 TOPS Deburst tool. Then I do SAR Simulation,SNAP error:
A problem occurred during the target product initialisation.
Type:OperatorException
Message:incidence_angle tie point grid not found in product.
GETASSE is one of the automatically downloaded DEMs which are supported by SNAP. If your area lies between 60° North and 60° South, I recommend to use SRTM 1Sec HGT (AutoDownload) whenever you can.
Has it worked to save all processing steps as BEAM DIMAP? It conserves the metadata required by some radar tools better than general formats. In the end you can still export to GeoTiff, please check the notes on this in this tutorial: Export of products from SNAP