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Tripole antenna in LOFAR CS011

Submitter: Linjie Chen, Menno Norden
Description: Sky radio emission below 10 MHz is inaccessible from the surface on Earth due to the absorption and scattering in the ionosphere. To explore this region of the electromagnetic spectrum, a space-based radio telescope would be required. The far side of the Moon is shielded from the Earth's radio interference and offers a very large and stable platform for a radio observatory. With the rapid development of lunar exploration, it is feasible to build a Moon-based astronomy facility.

In the very first lunar missions, a very low frequency radio interferometer can be implemented with a lander and a rove to get a degree-level angular resolution. Even with a single antenna, there are several experiments which could be done: measure the meteoritic impacts (bright radio pulses on ms time scales); measure the cosmic rays (pulses on 0.1 us time scale); monitor the RFI situation and ionospheric cutoff frequency on the Moon.

Based on these motivations, an active tripole antenna has been developed as the Moon antenna prototype. To verify its performance, the tripole antenna has been installed at the LOFAR core station CS011 and it has been involved in some test observations. During the last four months, a lot of data have been obtained with the tripole antenna and other LBAs in CS011, that include 24-hour spectra of the sky background, RFI monitoring, and lightning detections. These data will be used to analyse the antenna sensitivity, and test the antenna capability of DOA estimates for RFI and transient radio sources. Similar experiments will be amongst the first to be carried out in the observational programmes of future Moon-based radio astronomy facilities. The insets show results of the monitoring conducted at the CS011 site with the tripole antenna.

The work described here is a part of the PhD project by the undersigned (”Research on a Moon- based Very Low Frequency Radio Interferometer”), funded by the Joint PhD Training Programme of the Royal Dutch Academy of Science (KNAW) and the Chinese Academy of Sciences (CAS).

Great thanks to Menno Norden and Jan Nijboer (ASTRON) for their assistance of the antenna setup and measurements!
Copyright: L.Chen / JIVE, ASTRON, Radboud University and NAOC
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