Orbiting Low Frequency Array for radio astronomy

Recently new and interesting science drivers have emerged for very low frequency radio astronomy from 0.3 MHz to 30 MHz. However Earth bound radio observations at these wavelengths are severely hampered by ionospheric distortions, man made interference, solar flares and even complete reflection below 10 MHz. OLFAR is Orbiting Low Frequency ARray, a project whose aim is to develop a detailed system concept for space based very low frequency large aperture radio interferometric array observing at these very long wavelengths. The OLFAR cluster could either orbit the moon, whilst sampling during the Earth-radio eclipse phase, or orbit the Earth-moon L2 point, sampling almost continuously or Earth-trailing and leading orbit. The aim of this paper is to present the technical requirements for OLFAR and first order estimates of data rates for space based radio astronomy based on the proposed scalable distributed correlator model. The OLFAR cluster will comprise of autonomous flight units, each of which is individually capable of inter satellite communication and down-link. The down-link data rate is heavily dependent on distance of the cluster from Earth and thus the deployment location of OLFAR, which are discussed.