Mercury Computer Systems Inc. said Wednesday Russell K. Johnsen has resigned form his post as chairman of the company's board.
Mercury, which makes computer systems and software, said it has appointed Vincent Vitto to take his place. Vitto has served on the board since he retired from his former position as CEO of Draper Laboratory, a nonprofit engineering lab, in 2006.
The company did not disclose why Johnsen decided to step down, but said he recently took the job of president at USfalcon Inc., a defense contractor. Calls seeking comment were not immediately returned Wednesday.
Johnsen had served on the Mercury's board since 2001 and was elected chairman in 2008.