Visual Brightness Characteristics of Starlink Generation 1 Satellites

TL;DR

This paper analyzes the visual brightness characteristics of Starlink Generation 1 satellites, deriving phase functions and a characteristic magnitude metric to compare different satellite designs' brightness profiles.

Contribution

It introduces a comprehensive analysis of brightness phase functions for Starlink satellites and defines a new metric for comparing their brightness levels.

Findings

Original satellites have a characteristic magnitude of 4.7.

VisorSat satellites are dimmer with a characteristic magnitude of 6.2.

Post-VisorSat satellites have an intermediate brightness with a characteristic magnitude of 5.5.

Abstract

A large dataset of visual magnitudes for all three designs of Starlink satellites is analyzed. Brightness phase functions are derived for the Original, VisorSat and Post-VisorSat models. Similarities and differences between the functions for these spacecraft are noted. A metric called the characteristic magnitude is defined as the average brightness of a satellite when seen overhead at the end of astronomical twilight. When the phase functions are evaluated according to this metric, the characteristic magnitudes are: Original, 4.7; VisorSat, 6.2; and Post-VisorSat, 5.5.