  Modeling the brightness of satellites in large Low-Earth Orbit (LEO)
constellations can not only assist the astronomical community in assessing the
impact of reflected light from satellites, optimizing observing schedules and
guiding data processing, but also motivate satellite operators to improve their
satellite designs, thus facilitating cooperation and consensus among different
stakeholders. This work presents a photometric model of the Starlink satellites
based on the Bidirectional Reflectance Distribution Function (BRDF) using
millions of photometric observations. To enhance model accuracy and
computational efficiency, data filtering and reduction are employed, and
chassis blocking on the solar array and the earthshine effect are taken into
account. The assumptions of the model are also validated by showing that the
satellite attitude is as expected, the solar array is nearly perpendicular to
the chassis, and both the solar array pseudo-specular reflection and the
chassis earthshine should be included in the model. Reflectance characteristics
of the satellites and the apparent magnitude distributions over station are
finally discussed based on the photometric predictions from the model. In
addition to assessing the light pollution and guiding the development of
response measures, accurate photometric models of satellites can also play an
important role in areas such as space situational awareness.
