Brightness Characterization for Starlink Direct-to-Cell Satellites

TL;DR

This study measures and compares the brightness of Starlink DTC satellites, finding they are generally brighter than other Starlink satellites, with implications for astronomical observations and potential mitigation strategies.

Contribution

It provides the first detailed brightness characterization of Starlink DTC satellites and analyzes factors influencing their brightness and observational impact.

Findings

DTC satellites are on average 4.9 times brighter than other Starlink Minis.

Estimated brightness increase of DTCs is about 2.6 times under certain assumptions.

DTCs spend more time in Earth's shadow, reducing some observational impact.

Abstract

The mean apparent magnitude of Starlink Mini Direct-To-Cell (DTC) satellites is 4.62 while the mean of magnitudes adjusted to a uniform distance of 1000 km is 5.50. DTCs average 4.9 times brighter than other Starlink Mini spacecraft at a common distance. We cannot currently separate the effects of the DTC antenna itself, the different attitude modes that may be required for DTC operations and to what extent brightness mitigation procedures were in place at the times of our observations. In a best case scenario, where DTC brightness mitigation is as successful as that for other Minis and the DTC antenna does not add significantly to brightness, we estimate that DTCs will be about 2.6 times as bright as the others based upon their lower altitudes. The DTCs spend a greater fraction of their time in the Earth's shadow than satellites at higher altitudes. That will offset some of their impact on astronomical observing.