I'm trying to add rasters to a mosaic - I was initially trying to do this by background processing but I was receiveing an error - I've followed the advice of this article (http://support.esri.com/en/knowledgebase/techarticles/detail/38695) (turning off background processing/turning off the option to add geoprocessing results to the display) but I still can't get it to work - now instead of returning an error message ArcMap just shuts down with no warning.
using Arcmap 10.1 you can use an alternative option:
- add your all geo-refed raster in a new arcmap
- define the projection properly in the data frame properties
- Go to windows menu and click on image analysis.
- In image analysis tool select all your rasters and click on mosaic button present in a window below named "processing".
- A temporary raster add in table of contents, finally export it in tif or img format because you have 16bit data.