Lander pooling and data collection principle for future planetary missions

Abstract Future in-situ planetary missions will probably be based upon the use of several Landers located on the surface or in the area of the visited planet in association with one ore more satellites put in circular or elliptical orbit around the planet. The Landers can be fixed platforms like small stations or penetrators or mobile vehicules like balloon or rover. Each Lander must be considered as a data source which must be collected and transmitted to the Earth either directly or indirectly through the orbiting satellite. In addition it can be interesting to perform Lander positioning in order to more accuratly identify the situation of the operating region; this possibility can be of higher interest for balloon or rover which are continuously moving during the mission. In addition, fixed Landers can be used as a positioning and orbit determination basis in order to improve satellite ephemerids determination. A topical exemple for such missions is given by the Russian mission Mars 96 which includes the deployment from the orbiter of two small Stations und two Penetrators on the Mars planet at the end of year 97. These Landers will be linked to Earth through two telecommunication relays located onboard Mars 96 satellite to be launched by Russia und Mars Global Surveyor satellite to be launched by the United States, both at the end of year 1996. The relays are provided to these projects by the French space agency. Centre National d'Etudes Spatiales (CNES). The present paper wHich topics are based on the relay mission1 of these two projects is related to the analysis of the pooling, data collection and localization problems from an orbiting satellite, this satellite being in direct communication with several Landers or other moving vehicules located on the planet. Relevant parameters related to data transmission and positioning problem are identified and description of some possible method for data retrieval needs is proposed for future planetary missions.