NORTHAMPTON, Mass., Feb. 4 -- Kollmorgen Corp. of Northampton is being awarded a $13.5 million modification to a previously awarded US Navy contract. Kollmorgen designs submarine periscopes, optronics and masts, as well as weapon systems for surface ships, combat vehicles and other defense platforms. The original contract from The Naval Sea Systems Command in Washington, D.C., is for engineering services and production of the universal modular mast system for installation on Virginia and SSGN class submarines. The UMM is a nonhull penetrating mast that raises and lowers sensors. Work will be performed in Northampton and in Bologna, Italy, and is expected to be completed in December.