In astronomy, ultra-high angular resolution has always been a crucial tool for fundamental discovery. New momentum in high angular resolution astrophysics was provided by the millimeter VLBI system's Event Horizon Telescope's direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 and a number of pioneering results from the Space VLBI mission RadioAstron. The angular resolution was approximately 10–20 microarcseconds (0.05–0.1 nanoradians) in both of these instances. The requirements of advanced astrophysical research necessitate further progress toward "sharper" values of at least one order of magnitude at the level of one microarcsecond. The paper emphasizes that placing millimeter and submillimeter wavelength interferometric systems in space is the only way to achieve these higher values. In the context of the ESA Call for White Papers for the Voyage 2050 long-term plan in 2019, a concept of this kind of system has been proposed. It is called Terahertz Exploration and Zooming-in for Astrophysics. Based on recent research on active galactic nuclei and supermassive black holes, we present new science objectives for this concept in the current paper. In addition, we go over a number of strategies for overcoming the technological obstacles that arise when building a space-based interferometric system at millimeter or submillimeter wavelengths. We focus on a novel space-borne millimeter/submillimeter antenna configuration that has the potential to overcome a number of obstacles to the creation of large, precise mechanical structures. In addition, a summary of potential space-qualified technologies for low-noise analog front-end instrumentation for millimeter and submillimeter telescopes is provided in this paper. Instrumentation for data handling and processing is another important technological part of a sub-millimeter Space VLBI system. This instrumentation's requirements and potential implementation options are extrapolated from the most recent, cutting-edge Earth-based VLBI data transport and processing equipment. The interferometric baseline state vector determination, synchronization, and heterodyning systems are also briefly discussed in this paper. The paper's technology-focused sections do not aim to present a comprehensive set of technological solutions for space-borne interferometers operating at terahertz (sub-millimeter) frequencies. Instead, when used in conjunction with the original ESA Voyage 2050 White Paper, it makes a stronger case for the next generation of microarcsecond-level imaging instruments and serves as a foundation for more in-depth studies of technology trade-offs.
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