PHM - Passive Hydrogen Maser is an atomic clock developed by Airborne and Space Systems Division, used for precise positioning, timekeeping and other onboard applications. Designed to operate in space for more than 12 years, it offers an outstanding stability for averaging times from 1 to 100,000 seconds. Airborne and Space Systems Division is also developing a mini PHM, which offers the same frequency stability as the PHM in a smaller package.