Influence of the phase of a spherical planet on determination of coordinates of albedo features on the planet's surface from ground-based observations

Abstract

A new method of determination of planetocentric coordinates of albedo features on the visible disc of a spherical planet is offered under various conditions of its illumination. The method is aimed for processing the images of planets received with ground-based telescopes. The position of a detail on the image of a planet is determined not concerning center of a geometric planetary disc, and concerning center of the illuminated part of its visible disc, that allows excluding influence of a phase of a planet. The auxiliary coordinate system connected to equator of intensity is applied for determination of a position of points on the illuminated part of a visible planetary disc. The formulae for transition from auxiliary coordinate system to planetocentric coordinate system are received. The particular cases of determination of planetocentric coordinates of basic points of the illuminated part of the visible disc of a spherical planet from the formulae, which are not requiring of attraction of auxiliary coordinate system, are considered. The method is checked up on an example of processing of the images of a Mercury and Mars.