Mobile satellite services (MSS) provide two-way voice and data communications to global users who are on the go or in remote locations; terminals range in size from handheld to laptop-size units. Terminals can also be mounted in a vehicle, with communications maintained while the vehicle is moving. MSS operates at L-band—low enough in the frequency spectrum to avoid the rain fade associated with higher bandwidth Ku- and Ka-band fixed satellite systems. (Note: Ku and Ka bands are used for a limited set of similar applications, but typically have much larger terminals; more focused beams also result in the need for the terminal to track the satellite.)