Antenna Arrays for High Data Return from Future Deep Space Missions

Abstract

Future missions will be more demanding than present ones (larger link distances, higher data rates, limited on board communication performances of landers and rovers to be compensated by the ground station antenna …). Present capabilities of ESA Deep Space Antennas, being the state of the art of today's technology, sometimes struggle to provide the performances required by the missions. Future missions will need an improvement of the performances of the Deep Space Antennas but the present technology based on large parabolic reflectors almost reaches its limits. Two ESA studies have analyzed the different solutions for future Deep Space Antennas, like the extension of the present concept to larger dishes and the arraying of few big antennas in reception or higher transmitter power levels in transmission. The final solution involving arraying of large parabolic dishes is described with special focus on the new possibilities of operation offered by an array of antennas. The Array capabilities can be shared between missions in a dynamic way by distributing the total performance of the array (G/T) between different missions with the allocation of a fraction of the ground station to each one of several simultaneously supported missions in function of the required G/T of each mission. The multimission support will allow not only a larger number of station support hours but also cost savings for the missions by sharing the cost of the station. I. Introduction ESA 35 m Deep Space Antennas are equipped with the state of the art technology for Deep Space communications. The present requirements of ESA Deep Space antennas (107 dBW EIRP and 50 dB/°K G/T in X band) are based on present missions requirements. New missions will be more demanding for the ground stations: Cosmic Vision missions to Jupiter-Saturn will require increased data downlink rates from very distant probes; manned missions demand much higher (and bidirectional) link capability to allow video and audio; lander/rover/penetrator missions are very limited on resources on board (small antenna and little power) and the link must be compensated with better performances of the ground station; multilink operations require the distribution of the ground station capabilities between the different missions. Emergency situation will benefit also of more performing ground stations. An improvement of the performances of the ground station’s deep space antennas in the order of 6 to 10 dB would be needed for future missions. Unfortunately present technology is reaching its limits. A trade-off between the present concept for Deep Space antennas with larger dishes - higher transmitted power and new architectures (like arraying few big antennas) or even hybrid solutions shall be performed to conclude with the best option. More futuristic approaches like arraying of many (100's) small antennas, not only for reception but also even for transmission, shall be also considered for the long term. The results of the trade-off provides the description of the best architecture , its performances, the feasibility of the solution, the cost, and a roadmap for the future possible implementation. ESA has supported in the frame of the General Studies Program two parallel studies