Low data volume satellite communication system

A communication terminal suitable for sending burst messages to network infrastructure in a communication system, the network infrastructure having a receiver, the terminal comprising: 5 a transmitter configured to transmit the burst messages to the network infrastructure, the burst messages including a pilot waveform; the pilot waveform comprising a series of repeated short sequences modulated to add time spacing of varying length between the repeated short sequences, wherein the time spacing is arranged such that an in-phase correlation peak has significantly higher magnitude 10 than out-of-phase correlation peaks at the network infrastructure receiver.