Ground-based radio telescopes are routinely used to search for light dark matter (DM) candidates such as axionlike particles or dark photons. However, these instruments face inherent limitations to push the searches to masses below 10-7 eV, due to the effect of the Earth's ionosphere. The extant and planned space- or Moon-based radio telescopes motivate this study: We systematically investigate their sensitivity to resonant conversion of light DM into radio signals from three solar system targets: the Sun, the Earth, and Jupiter. The perspectives are especially encouraging for dark photon searches using the Sun as a target, and for axionlike particles conversion in Jupiter's magnetosphere.