Patent ID: 6915106

Claim:
A digital satellite communications system for communicating data between a HUB station and a plurality of VSATs (Very Small Aperture Terminals) or between the VSATs via a communications satellite, wherein each VSAT comprises: a digital signal processing means for demodulating signals which are received by the VSAT; nonvolatile memory for storing a default program for letting the digital signal processing means execute signal demodulation at start-up of the VSAT; rewritable memory for storing an operation program for letting the digital signal processing means execute signal demodulation after the start-up of the VSAT; an operation program download means for obtaining the operation program by downloading the operation program from the HUB station; an error check/rewriting means for conducting error check to the operation program downloaded from the HUB station until an errorless operation program is obtained by the download and storing the errorless operation program in the rewritable memory; and a switching control means for switching a program which is loaded into and used by the digital signal processing means from the default program to the operation program; wherein the switching control means switches the program which is loaded into and used by the digital signal processing means from the operation program to the default program when reception synchronization between VSATs cannot be established.