An Implementation of Concatenated Coding Scheme on Indian Spacecraft

Abstract

A Concatenated Coding Scheme to provide an extremely 'clean' channel is suggested for onboard spacecraft telemetry system by the Consultative Committee for Space Data Systems (CCSDS). The outer code is a Reed Solomon block code and the inner, a Viterbi or Convolutional Code. The Gaussian channel are corrected by the inner code. However, the Viterbi decoder may introduce some burst errors. These are then corrected by the Reed Solomon decoder. The inner Viterbi code (K=7, rate 1/2) was developed and implemented for the first time in RSD2 (Rohini series) satellite. The outer code has not yet been implemented onboard spacecraft since the decoder has not been fully developed. However, the onboard encoding system (255,223) has been developed and tested. This paper describes the development and implementation of Viterbi encoder in RSD2 satellite along with its inorbit performance.