I'm afraid that atmospheric correction of WV3 SWIR data is not supported in Geomatica. WV3 comes with two separate files; one MS and PAN and the other SWIR. In order to run ATCOR on SWIR bands you need MS bands as well. However, in the case of WV3 the pixel sizes for the SWIR data and MS data are different and these files cannot be merged. Unfortunately, you cannot run ATCOR on just the SWIR data as you will get an error, asking for a red band.