Reply to the Comment by B. Campbell on the Paper “Regolith Layer Thickness Mapping of the Moon by Radar and Optical Data”

✍ Scribed by Yu.G. Shkuratov; N.V. Bondarenko

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 56 KB
• Volume: 158
• Category: Article
• ISSN: 0019-1035
• DOI: 10.1006/icar.2002.6890

✦ Synopsis

We are grateful to Dr. B. Campbell for his comment, as this gives an opportunity to discuss once again important problems concerning radar studies of the lunar surface and to compare the two model approaches presented in (Campbell et al. 1997) and our paper (Shkuratov and Bondarenko 2001).

Before we consider Campbell's criticism, we would like to make a general remark about the models we used. Our knowledge about the first few meters of the regolith is extremely poor and nobody has constructed a rigorous model of radar scattering the lunar surface. Therefore, one has to resort to heuristic "first-order" models, which do not require detailed information about the regolith structure but still could predict some quantities of interest. Then, working with the heuristic models, one often has to replace the scarcity of the available information with a guess of model parameters. For example, Campbell et al. (1997) used the averaged Mie backscatter cross sections and single scattering approximation to estimate scattering by buried rocks, though the cross sections of arbitrary shaped stones have nothing in common with the cross section of a perfect sphere and the ignoring of multiple scattering of radar waves is not justified. The model of Campbell et al. (1997) neglects also polarization effects of radar wave scattering and roughness of the lunar surface. Nevertheless, all these shortcomings do not weaken the validity of the model by Campbell et al. (1997) as a "first-order" model.

The criticism will be discussed in more detail, as follows.