Brightness Characteristics of the Qianfan Satellites and Evidence That Some Are Tumbling

TL;DR

This study analyzes the brightness and tumbling behavior of the Qianfan satellites, revealing their impact on astronomy and the importance of understanding their light characteristics.

Contribution

It provides the first detailed brightness measurements and evidence of tumbling in Qianfan satellites, highlighting their potential impact on astronomical observations.

Findings

Mean apparent magnitude is 5.76

Light curves show rapid periodic fluctuations indicating tumbling

Most non-tumbling satellites have Earth-facing diffuse surfaces

Abstract

The mean apparent magnitude of the Qianfan satellites is 5.76 +/- 0.04, while the mean of magnitudes adjusted to a distance of 1,000 km is 5.24 +/- 0.04, based on 1,161 observations. Light curves of several spacecraft display rapid periodic fluctuations which indicate that they are tumbling. Nearly all of the non-tumbling satellite observations can be modeled with diffusely reflecting, Earth-facing surfaces. The Qianfan constellation will impact astronomical research and aesthetic appreciation of the night sky unless their brightness is mitigated.