The meteorological data distribution mission on board SIRIO satellite

The SIRIO 2 meteorological data distributor mission and the related telecommunication package, comprising an S band repeater and a despun antenna system assembly are described. The repeater assembly receives and amplifies signals via a low noise amplifier, down converts them to an intermediate frequency (IF) and amplifies these signals at IF, to generate a TLM carrier phase modulated by the PCM signals from the on board telemetry encoder. It sums the IF signal and the TLM carrier and up converts them to an S band frequency, and provides power amplification of the composite signal for retransmission. The despun antenna system functions are: provide a beamwidth at the reveive and transmit frequency bands sufficient to meet the coverage requirements; provide gain over the coverage at the receive and transmit frequencies; and acquire and maintain the pointing of the beam towards Earth during all mission lifetime by despinning the antenna structure with a rotary motion having the same satellite angular speed but opposite direction.