Radio astronomy with the European Lunar Lander: Opening up the last unexplored frequency regime

Abstract

The moon is a unique location in our solar system and provides important information regarding the exposure to free space that is essential for future human space exploration to mars and beyond. The active broadband (1 kHz−100 MHz) tripole antenna now envisaged to be placed on the European Lunar Lander located at the Lunar South Pole allows for sensitive measurements of the exosphere and ionosphere, and their interaction with the Earths magnetosphere, solar particles, wind and CMEs and studies of radio communication on the moon, that are essential for future lunar human and science exploration. In addition, the lunar South pole provides an excellent opportunity for radio astronomy. Placing a single radio antenna in an eternally dark crater or behind a mountain at the south (or north) pole would potentially provide perfect shielding from man-made radio interference (RFI), absence of ionospheric distortions, and high temperature and antenna gain stability that allows detection of the 21 cm wave emission from pristine hydrogen formed after the big bang and into the period where the first stars formed. A detection of the 21 cm line from the moon at these frequencies would allow for the first time a clue on the distribution and evolution on mass in the early universe between the Epoch of Recombination and Epoch of Reionization (EoR). Next to providing a cosmological breakthrough, a single lunar radio antenna would allow for studies of the effect of solar flares and Coronal Mass Ejections (CMEs) on the solar wind at distances close to earth (space weather) and would open up the study of low frequency radio events (flares and pulses) from planets such as Jupiter and Saturn, which are known to emit bright (kJy−MJy) radio emission below 30 MHz (Jester and Falcke, 2009). Finally, a single radio antenna on the lunar lander would pave the way for a future large lunar radio interferometer; not only will it demonstrate the possibilities for lunar radio science and open up the last unexplored radio regime, but it will also allow a determination of the limitations of lunar radio science by measuring the local radio background noise.

Antenna design and implementation for the future space Ultra-Long wavelength radio telescope

“…Recently, many other concepts have been presented for exploring the ULW region. These range from a single satellite element (DARE [10] and LRX [38]) to swarms of small satellites forming multi-element interferometers (FIRST [7], SURO-LC [8], OLFAR [19], [28], DARIS [31]). Their locations cover the lunar surface, lunar orbit, the Sun-Earth L2 point, etc.…”

“…In the ESA report [6] a 4 m active dipole antenna was suggested as a receiving element for the ULW array on the lunar far side. In other recent studies [7], [8], [10], [19], [38], dipole antennas have also been considered for ULW astronomy. For the ULW antenna design, discussed different antenna concepts operating from 1 to 10 MHz have been discussed in 2007 with the conclusion that a non-matched dipole is acceptable for the space-borne radio astronomy [3].…”

Prospects of probing the radio emission of lunar UHECRv events

“…The experiment was designed to observe radio emissions on the lunar surface including UHECRv radiation. Technical requirements and science cases of LRX are described in (Klein-Wolt et al, 2012;Zarka et al, 2012). An individual antenna is used for both the lunar orbiter and the lunar surface experiments in this study.…”

“…A tripole antenna is a preferred choice for individual antennas onboard the lunar orbiter satellites and lunar lander (Stål, 2007;Klein-Wolt et al, 2012). It consists of 3 co-centred orthogonal dipoles which enables it to detect signals in all directions.…”

“…Impact of lunar dust, charged particles, and micro-meteorites generate radio pulses which cover a broad range of spectrum from kHz to GHz regime (Grimalsky et al, 2004). It has local peaks at kHz regime which are detectable by the antenna, Dust camera, and Langmuir probe (Klein-Wolt et al, 2012). Those events occurring near the antenna generate pulses which could be confused with UHECRv events for the lunar surface observations.…”