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We have developed, manufactured, and tested a new feed design for interferometric radio telescopes with "large-N, small-D" designs. Such arrays require low-cost and low-complexity feeds for mass production on reasonable timescales and budgets, and also require those feeds to be compact to minimize obstruction of the dishes, along with having ultra-wide frequency bands of operation for most current and future science goals. The feed presented in this paper modifies the exponentially tapered slot antenna (Vivaldi) and quad-ridged flared horn antenna designs by having an oversized backshort, a novel method of maintaining a small size that is well-suited for deeper dishes (f ∕ D ≤ 0. 2 5). It is made of laser cut aluminum and printed circuit boards, such that it is inexpensive (≲ 7 5 USD per feed in large-scale production) and quick to build; it has a 5:1 frequency ratio, and its size is approximately a third of its longest operating wavelength. We present the science and engineering constraints that went into design decisions, the development and optimization process, and the simulated performance. A version of this feed design was optimized and fabricated for the Canadian Hydrogen Observatory and Radio-transient Detector (CHORD) prototypes. When simulated on CHORD's very deep dishes (f ∕ D = 0. 2 1) and with CHORD's custom first-stage amplifiers, the on-sky system temperature T sys of the complete receiving system from dish to digitizer remains below 30 K over most of the 0.3–1.5 GHz band, and maintains an aperture efficiency η A between 0.4 and 0.6. The entire receiving chain operates at ambient temperature. The feed is designed to slightly under-illuminate the CHORD dishes, in order to minimize coupling between array elements and spillover. [ABSTRACT FROM AUTHOR]

This paper is about the Data Processing Center (DPC) working within the RadioAstron project. Since the launch of the space radio telescope to orbit in July 2011, the DPC underwent significant quantitative and qualitative changes as the project developed. This paper describes the schemes, structure, stages of the processing center development, current upgrades and new technologies introduced in the DPC throughout the entire period of its operation. For technical reasons, the scheduled observations in the project were terminated in January 2019. However, still the work of the DPC continued. Today, the most valuable thing we have is information. There is now a unique archive of service and scientific data of the project in our possession, and a data bank of the RadioAstron project is underway, which will ensure a proper access to scientific and service information for all interested experts, as well as provide an opportunity for an additional data analysis. [ABSTRACT FROM AUTHOR]