I just tried to view some of the Met information in SNAP from this products:
S3A_SL_1_RBT____20170825T085514_20170825T085814_20170826T155622_0180_021_249_5579_MAR_O_NT_002.SEN3
The fields that I tried to view (TCWV, spec humidity, temperature) come up blank. I can see values in these though if I read the nc file using IDL program.