Brightness of the Qianfan Satellites

TL;DR

This paper models the brightness variations of Qianfan satellites based on their orientation and surface properties, highlighting potential impacts on astronomical observations.

Contribution

It introduces a model for satellite brightness using Lambertian reflectance of specific surfaces, aiding in understanding and mitigating their impact on astronomy.

Findings

Brightness varies from magnitude 4 to 8 depending on position.

Model accurately predicts observed brightness based on satellite orientation.

Surface reflectance properties are key to brightness levels.

Abstract

Observed magnitudes of Qianfan spacecraft range from 4 when they are near zenith to 8 when low in the sky. Nearly all of the observations can be modeled with a nadir-facing flat antenna panel and the underside of a zenith-facing solar array, both with Lambertian reflectance properties. These satellites will impact astronomical research unless their brightness is reduced.