On the photometry of geostationary satellites near the equinox dates

Long-term photometric observations (on scales of half a year to one year) at different positions of geostationary satellites (GSS) relative to an observer are necessary to determine photometric, optogeometrical, and dynamic characteristics of faint GSSs needed to be identified. We propose to perform photometric measurements of GSSs during their ingress into and egress from the Earth’s shadow near the equinox dates. At the equinoxes, the GSS brightness is several magnitudes higher, making it possible to effectively use telescopes with mirror diameters of 50–70 cm. A much larger amount of information on reflective properties of an object can be derived during observation on these dates than when performing long-term observations at large phase angles.