ON THE SIMPLE MODELS FOR THE INTERPRETATION OF CENTIMETER-WAVELENGTH RADIO OBSERVATIONS OF ASTEROIDS

The predictions of the two-layer models used to interpret radio spectra of the asteroids have been examined. It is clear that one must treat the models with caution as the physics is highly simplified. Although the predictions are in accord with physical expectations, careful attention to the circumstances of the observations is essential. The lack of short-centimeter wavelength measurements of dielectric properties is especially vexing. Some simple improvements to the models based on studies of the lunar radio emission by Keihm and using radar measurements of asteroid surface characteristics by Ostro and colleagues are suggested. Even so, the calculation of a realistic continuum-emission spectrum for asteroidal bodies from 20 cm wavelength to 20 microns wavelength remains a formidable task.