Assessment of Brightness Mitigation Practices for Starlink Satellites

TL;DR

This paper reviews the photometric characteristics of Starlink satellites, highlighting how SpaceX's brightness mitigation techniques have effectively reduced luminosity, but some impact on astronomy remains, especially with larger future satellites.

Contribution

It provides a comprehensive analysis of Starlink satellite brightness mitigation methods and their effectiveness across different models and generations.

Findings

Brightness mitigation reduces satellite luminosity by up to a factor of 3.

VisorSat design significantly decreases brightness compared to original models.

Larger Generation 2 satellites are still brighter but less so than their size would suggest.

Abstract

Photometric characteristics for all models of Starlink satellites launched to date are reviewed. The Original design that lacked brightness mitigation is the most luminous. SpaceX installed a sunshade on the VisorSat model which reduced its luminosity by a factor of 3. The visor was omitted on Post-VisorSat spacecraft with laser communication which followed, but the company added a reflective layer which resulted in an intermediate brightness between Original and VisorSat. SpaceX is applying advanced brightness mitigation techniques to their Generation 2 Starlink satellites which are larger. The first of these, called Minis, are dimmer than Gen 1 Starlinks despite their greater size. Photometric observations verify that brightness mitigation efforts employed by SpaceX reduce spacecraft luminosity substantially. However, the satellites still have some negative impact on astronomical observations and the very large satellites planned for later in Gen 2 may interfere more seriously.