Setting up an observatory on the Moon could not only give us new views of the universe, but also inspire the billions of people who look at the Moon. Such a project will utilize the same transportation, communication, and power systems required for further exploration of the Moon. The lunar surface provides unique advantages for astronomy, even compared to orbits or Lagrange points. It is a large and stable platform that can shield unwanted radiation and that will be easily accessible once a lunar base is established. Astronomy from the Moon has been advocated since at least the mid-1960s. The most seriously investigated concept has always been a very-low-frequency (VLF) array on the lunar far side for mainly three reasons. First, the very low frequencies below ~30 MHz is the last window in the electromagnetic spectrum yet to be explored in astronomy, giving us good reasons to anticipate unexpected discoveries. Second, because of Earth's significant radio interference, the lunar far side may well be the only site accessible that enables sensitive galactic / extra-galactic VLF observations. Finally, an array of short dipole antennas is one the most technologically feasible observatories to be placed and operated on the Moon. The motivations for a lunar based VLF array is detailed in the first section. The second section provides a review of the foregoing effort and a summary of the consensus to date.

To make this dream into a reality, we identify the next required steps in the third section. We must first address any unresolved issues, especially concerning the lunar environmental factors like the ionosphere density. We should make the most out of the upcoming lunar missions by proposing relevant measurements. Most importantly, we should begin proposing our first array now. Considering the limited budget, the first realistic surface array will be deployed as a piggyback payload to early landers on the lunar south pole. The side of the Malapert Mountain that is facing away from Earth may be a good radio-quiet site.

To address issues relevant to the lunar VLF array project, we have developed a general tool to simulate the propagation of radio waves in the lunar environment. In this study, we investigated (1) how well the Moon shields long-wavelength radio interference, (2) how the Malapert Mountain at the lunar south pole shields terrestrial radio interference, and (3) how the lunar surface environment influence interferometric observations. These radio wave simulation studies and their results are presented in the fourth section.

Finally, in the last section, we make recommendations for future missions and propose the first surface array to be deployed on the far side of the Malapert Mountain near the lunar south pole. To finalize the site and the design of the observatory, recommendations are presented for specific measurements to be made by upcoming missions including SMART-1, LunarSat, and SELENE. It is especially critical to obtain detailed topology at candidate sites and to determine the electron density profile above the lunar surface at various times of the lunar month. Suggestions are given for a precursor orbiting array around 2010, a surface array on the lunar south pole around 2015, and ultimately a far side array around 2020. To realize the dream of gaining new views of the universe from the Moon, it is time for an international team to begin seriously proposing these missions.

1. 53rd IAC

2. First Submission

3. A Lunar Far Side Radio Array as the First Astronomical Observatory on the Moon

4. TAKAHASHI, Y.D.

5. IAC-02-Q.4.3. Joing Session with COSPER on Exploration of, on, and from the Moon

6. D.A. O'HANDLEY, B.H. FOING

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8. Word file sent by e-mail

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