Olfar: orbiting low frequency antenna for radio astronomy

New interesting astronomical science drivers for very low frequency radio astronomy have emerged, ranging from studies of the astronomical dark ages, the epoch of reionization, exoplanets, to ultra-high energy cosmic rays. However, astronomical observations with Earth-bound radio telescopes at very low frequencies are hampered by the ionospheric plasma, which scatters impinging celestial radio waves. This effect is larger at lower frequencies. Below about 5 MHz at night or about 10 MHz during daytime, the ionosphere is even opaque for radio waves. That means that Earth-bound radio astronomy observations in those bands would be severely limited in sensitivity and spatial resolution, or would be entirely impossible. A radio telescope in space would not be hampered by the Earths ionosphere, but up to now such a telescope was technologically and financially not feasible. However, extrapolation of current technological advancements in signal processing and small satellite systems imply that distributed low frequency radio telescopes in space could be feasible. We propose an autonomous distributed sensor system in space to explore this new low frequency band for radio astronomy. The array will have identical elements (satellites), and ideally no central processing system. An advantage of such a system is that it is highly scalable and, due to the distributed nature, virtually insensitive to failure or non-availability of a fraction of its components. In this paper we present this novel concept of OLFAR, the orbiting low frequency antennas for radio astronomy in space.