Remote Sensing of the Zodiacal Cloud along Secants to Earth’s Orbit

Abstract

Partial but significant localization along the line of sight (l.o.s.) of the contributions to the integrated zodiacal brightness can be achieved, without recourse to rash physical assumptions, if we focus on the two intersections between the l.o.s. and the terrestrial orbit, Then, there exists on the l.o.s. two other points or “nodes”, the contributions of which can be retrieved with outstandingly low uncertainty. The photometric results at these nodes (heliocentric change of scattering efficiency, backscattering phase function etc.) are highly reminiscent of previously ascertained features, and they encourage extensions to the polarimetric, the spectrometric and the radiometric cases. The salient results are, respectively: a positive radial gradient of local polarization degree; orbital velocities in excess over the keplerian ones, at least outside the earth’s orbit; the derivation of local temperatures from IRAS data.