Constellations of MEO Satellites and Their Observability as Telescopes

A recently introduced large-scale communication-satellite-based radio astronomy system offers several advantages in terms of radio frequency interference, available radio astronomy observation (RAO) bands, bandwidth, and observability. However, a dual-purpose satellite with communication and cosmic radio signal sensing capability incurs a much higher cost than a communication satellite. This problem motivates us to explore hybrid constellations of medium Earth orbit (MEO) satellites consisting of a mixture of single- and dual-purpose satellites to keep the cost low. In particular, we consider six configurations of half dual-purpose MEO (DMEO) satellites where one-half of the satellites are dual purpose and six configurations of quarter DMEO satellites where a quarter of the satellites are dual purpose. Based on the positioning of DMEO satellites on orbital planes, all the considered configurations fall into three general categories, i.e., unilaterally clustered, evenly distributed, and the combination of clustered and distributed configurations. We investigate two representative scenarios of RAO regions for the satellites, namely, the night hemisphere region and the Earth blockage region. We evaluate projected maximum baseline distance and (u, v) coverage of the configurations as they define the angular and spatial resolutions of the interferometric observation by the DMEO telescopes. Our investigation provides interferometric characteristics of the configurations and guidelines for the choice. The most suitable configuration changes with the RAO source direction, performance goal, and RAO region settings. Therefore, it needs to be chosen based on the overall RAO objectives during the lifetime of DMEO satellites.