Off-line Correlator for Antenna Array Over Long Baselines

This paper illustrates the design, implementation and testing of a prototype of an off-line correlator for large dish antenna array, in the frame of the ESA-funded study “Prototype of off-line Correlator for Arraying of Large Aperture Antennas” In order to improve the performance of downlink reception, a four 35-m antenna array is a valid alternative to a single large 70-m dish, offering the same performance with remarkable advantages, such as being more fail-safe against the failure of components. The concept is to acquire two or more replicas of the same signal at different Ground Stations and combine them after delay and phase correction, due mainly to media and clock offset. After a first study phase of the best combination and correlation methods, as well as of the requirements driven by the analysis of the error sources of delay and phase misalignment, the tool has been designed, implemented and successfully tested. Together with the correlator, a simulator has also been developed, in order to better test the performance of the combination tool. Tests with simulated, static (generated in ESOC) and real mission data have been carried out. The improvement in the Signal-to-Noise Ratio has been demonstrated, and the information bits have been successfully reconstructed after the combination of the deep space signal acquired in Cebreros and Malargüe stations from Exomars and Mars Express spacecraft, endorsing the tool for an off-line use in the near future.