Telemetry and command subsystem for a Mexican experimental microsatellite

A telemetry and command subsystem developed in Mexico is presented. The goal of this project is the design, construction, implementation and testing of a RF subsystem to be used on a digital communication link at 148 MHz (VHF band, uplink) and 400 MHz (UHF band, downlink), for the SATEX I microsatellite. The whole system consists of transmitter-receiver equipment for the satellite and its counterpart equipment for the master Earth station. The system also includes a minimal computation subsystem, which acts as a backup in case both the main and redundant onboard computers fail, generating a survival communications mode. Both terrestrial and space segments have an active (hot standby) 2:1 redundancy. A description of the developed prototype and its details are presented.