Optimization of time data codification and transmission schemes:   Application to Gaia
  Gaia is an ambitious space observatory devoted to obtain the largest and most precise astrometric catalogue of astronomical objects from our Galaxy and beyond. On-board processing and transmission of the huge amount of data generated by the instruments is one of its several technological challenges. The measurement time tags are critical for the scientific results of the mission, so they must be measured and transmitted with the highest precision - leading to an important telemetry channel occupation. In this paper we present the optimisation of time data, which has resulted in a useful software tool. We also present how time data is adapted to the Packet Telemetry standard. The several communication layers are illustrated and a method for coding and transmitting the relevant data is described as well. Although our work is focused on Gaia, the timing scheme and the corresponding tools can be applied to any other instrument or mission with similar operational principles. 
Jordi Portell (1 and 2), Enrique Garcia-Berro (1 and 2), and Xavier   Luri (1 and 3) ((1) Institut d'Estudis Espacials de Ca...