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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 Malargue stations from Exomars and Mars Express spacecraft, endorsing the tool for an off-line use in the near future.

The move towards higher frequency bands like 26GHz or 32GHz for scientific satellite data downlinks calls for the need to better characterise the atmosphere at the sites where ground antennas are located. For this reason ESA is undertaking the deployment of microwave radiometers at its Deep Space station locations. This paper reports the results of the first two years of site characterisation at the ESA Deep Space antenna 2 located in Cebreros, Spain.

We discuss the results achieved so far in the RESCUe (Reliable TTC b) non-coherent modulation schemes, like Frequency Shift Keying (FSK) and Differentially Encoded Phase Shift Keying (DPSK), as an alternative to coherent modulation schemes, like Phase Shift Keying (PSK); c) diversity techniques (space, time and frequency).

The Portable Radio Science Receiver (PRSR) is a suitcase-sized open-loop digital receiver designed to be small and easy to transport so that it can be deployed quickly and easily anywhere in the world. The PRSR digitizes, down-converts, and filters using custom hardware, firmware, and software. Up to 16 channels can be independently configured and recorded with a total data rate of up to 256 Mbps. The design and implementation of the system's hardware, firmware, and software is described. To minimize costs and time to deployment, our design leveraged elements of the hardware, firmware, and software designs from the existing full-sized operational (non-portable) Radio Science Receivers (RSR) and Wideband VLBI Science Receivers (WVSR), which have successfully supported flagship NASA deep space missions at all Deep Space Network (DSN) sites. We discuss a demonstration of the PRSR using VLBI, with one part per billion angular resolution: 1 nano-radian / 200 µas. This is the highest resolution astronomical instrument ever operated solely from the Southern Hemisphere. Preliminary results from two sites are presented, including the European Space Agency (ESA) sites at Cebreros, Spain and Malargue, Argentina. Malargue's South American location is of special interest because it greatly improves the geometric coverage for spacecraft navigation in the Southern Hemisphere and will for the first time provide coverage to the 1/4 of the range of declination that has been excluded from reference frame work at Ka-band.

Turbulence is an important effect for different applications including different aspects of electromagnetic propagation in the atmosphere, especially for frequencies in the microwave part of the spectrum. Our parameter of interest is an integrated effect, namely the propagation delay of a signal propagating through the Earth's atmosphere to a receiver on the ground. A simulation method has been implemented in order to predict the statistics of atmospheric turbulence. For systems where calibration for the wet delay is done by means of radiometric measurements there is an uncalibrated remainder of the variability due to imperfections of the method: (1) the radiometer location, which may not be identical to the location of the receiving antenna that is subject to calibration, (2) a pointing offset on the sky, and (3) the radiometer beam that may sense another volume of the air than does the original signal. The size of the remainder depends on the assumptions made about the atmospheric variability when the instrument is calibrated. The analysis shows that the overall performance of the system to a significant level depends on the uncertainty in the true range of variation for the turbulence strength parameter C n 2.

This paper presents the preliminary design of the Beam Waveguide (BWG) system of the 64-m diameter paraboloidal reflector antenna Sardinia Radio Telescope (SRT). The project is aimed at providing the antenna with Telemetry, Tracking & Command (TT&C) capabilities in order to support present and future deep-space missions. The synthesis of the BWG layout has been carried out according to the Gaussian Beam theory, which represents a reasonable compromise between accuracy of the results and computational time to set up the initial specifications of large reflector antennas. According to this assumption, the best design parameters of the antenna feeding system have been achieved through an accurate optimization analysis and verified by Physical Optics simulations. The proposed BWG architecture and the corresponding simulated antenna performance are shown in this paper.

The main focus of this study is the characterization of internal noise of the Microwave Radiometer (MWR) to be located at an ESA Deep Space Antenna (DSA) site, to accurately retrieve the tropospheric path delay along the line-of-sight of the deep space probe. This would enable precise tropospheric calibration of radiometric observables (range and range-rate) with particular reference to the BepiColombo SIC and the Cebreros (S) DSA. The characterization of current MWRs technologies has been based on a detailed analysis of data collected at Cabauw (NL) remote sensing site with the available instruments.

This paper describes the techniques currently in use and those proposed for a precise estimation of the Earth troposphere path delay for Deep Space probe tracking purposes. The different proposed techniques could be selected according to the to the mission goals and tracking accuracy requirements. In this paper, they are sorted by an increasing accuracy but also level of complexity.