Investigation of photometrical parameters features of space objects over a wide range of phase angles

Abstract

Observations of space objects over a wide range of phase angles allow to find out the brightness of space object changes under various conditions of the illumination and to investigate surfaces of space object inaccessible to the observer on small phase angels. Results of photometrical observations of spacecrafts and space debris in the range of phase angles from 0 to 140 degrees are presented. Observations were obtained with the 1.6-meter telescope AZT-33IK of Sayan observatory of ISTP SB RAS during 2015-2017. An analysis of magnitude dependence on phase angle reveals an increase in the brightness at phase angles above approximately 90 degrees which is characteristic of the operating spacecrafts in various types of orbit. A model of the brightness variation of spacecrafts at large phase angles was considered. We also give some examples of the brightness variations features of the non-operating spacecrafts under various illumination conditions and the brightness dependence on phase angle of space debris. The analysis of light curves of the rotating objects revealed the dependence of brightness changes of the space objects from conditions of illumination. These changes are identified in a form and amplitude of light curves.