Determining the master and slave in in the snap for interfrometry

Hello,
Since my study area is covered by two sentinel_1A products, to save processing time and processing steps, I tried to mosaic the images. For this reason, considering that my study method is interferometry using the PSI method, to determine the MASTER and SLAVES, one must be selected from the mosaicked images. However, while executing the command, considering that I have separately corrected both images for radiometric and terrain correction (Range-Doppler Terrain Correction), an error with the following statement appears:
Error: unable to read C:\RS\mosaic20150110.dim

Doppler Centroid Coefficients not found
After clicking OK, the error details appear:
Error: Index 0 out of bounds for length 0
Each image is attached separately
MOSAIC1



Hello
Since my study area is covered by two sentinel_1A products, to save processing time and processing steps, I tried to mosaic the images. Therefore, considering that my study method is PSI interferometry, to determine MASTER and SLAVES, it is necessary to select from the mosaicked images. However, while executing the command, considering that I have corrected both images separately for radiometric correction and terrain correction (Range-Doppler Terrain Correction), an error appears with the following statement:
Error: Unable to read C:\RS\mosaic20150110.dim

Doppler center coefficients not found
After clicking OK, the error details appear:
Error: Index 0 out of range for length 0
Each image is attached separately

Please help
Thanks