1. ESTEC 7 Dec 2007 1 Radio Properties of the Moon: a brief review of some important bits Graham Woan University of Glasgow

2. ESTEC 7 Dec 2007 2 lunar regolith Regolith electrical properties from Apollo missions: electrical conductivity ~10 -14 /Ohm/m at d.c. loss tangent ~0.001 to 0.1 at ~10 MHz relative permittivity ~6 Conductivity low enough to allow dipoles to be placed on the regolith without degrading beam pattern too severely (see later). dipole antenna pattern has largest lobe on the lunar side skin depth of between 1 and 100 (30 km at 1 MHz) possible trouble for subsurface reflections (from mascons etc)

3. ESTEC 7 Dec 2007 3 lunar exosphere Dual-frequency Luna spacecraft measurements give reasonably good evidence that an ionised layer, several kilometres thick, builds up on the illuminated side of the Moon (Vyshlov 1976) Max illuminated plasma frequency of ~0.5 MHz No layer seen during the lunar night Luna 22

4. ESTEC 7 Dec 2007 4 Dust Photo-ionisation may levitate dust electrostatically to give a “dust fountain”:

5. ESTEC 7 Dec 2007 5 Lunar opacity RAE-2 occultation of Earth

6. ESTEC 7 Dec 2007 6 Lunar opacity RAE-2 occultation of Sun

7. ESTEC 7 Dec 2007 7 Takahashi and Woan Radio propagation around the Moon, with subsurface penetration and a lunar density model Lunar opacity

8. ESTEC 7 Dec 2007 8 Takahashi and Woan Radio propagation at the Mapert Mountain (lunar south pole), with subsurface penetration and a lunar density model Lunar opacity

9. ESTEC 7 Dec 2007 9 Surface dipole field response

10. ESTEC 7 Dec 2007 10 unresolved lunar radio questions What is the electron ‘weather’ really like on the Moon? –Diurnal variations –Solar wind induced variations –Over the terminator What are the electrical properties of the regolith at likely sites? What is the true attenuation factor of the occulting Moon at the surface? What is the noise floor like on the dark, far-side surface? Can we achieve the dynamic range needed for HI surveying out to z~100-1000?

11. ESTEC 7 Dec 2007 11 What are the other current/planned investigations? Kaguya (Japan) and Chang’e 1(China) both have exosphere monitoring experiments, and plans for future lunar low-frequency experiments (see, e.g., Maohai Huang’s talk, IAU 26). More details needed!