[Paper Review] Starlink Satellite Brightness Before VisorSat

Anthony Mallama|arXiv (Cornell University)|Jun 15, 2020

Spacecraft Design and Technology1 references4 citations

TL;DR

This study presents the first comprehensive brightness measurements of Starlink satellites before the VisorSat design, analyzing 830 visual magnitudes at 550 km altitude. It finds a mean magnitude of 4.63 with significant variability, including extreme flares up to 10,000× brighter, and confirms DarkSat is 78% fainter than standard satellites, providing a critical pre-VisorSat baseline for assessing mitigation effectiveness.

ABSTRACT

The mean of 830 visual magnitudes adjusted to a distance of 550 km (the operational altitude) is 4.63 +/-0.02. The data on DarkSat, the low-albedo satellite, indicate that it is fainter than the others by 1.6 magnitudes or 78%. However, there is considerable uncertainty in this value due to the small number of observations. Some satellites were observed to flare by 10,000 times their normal brightness. These statistics can serve as a baseline for assessing the reduced brightness of the VisorSat design for future Starlink satellites.

Motivation & Objective

• To quantify the visual brightness of early Starlink satellites prior to the VisorSat design.
• To establish a pre-VisorSat brightness baseline for evaluating future mitigation strategies.
• To measure the brightness difference between standard Starlink satellites and the low-albedo DarkSat.
• To characterize transient flaring behavior in Starlink satellites.
• To provide observational data for assessing the impact of satellite constellations on ground-based astronomy.

Proposed method

• Collected visual magnitude observations of Starlink satellites from ground-based telescopes and visual observations.
• Adjusted all magnitudes to a standard distance of 550 km, the operational altitude of the satellites.
• Calculated the mean magnitude and standard deviation from 830 observations across multiple satellite passes.
• Compared the brightness of DarkSat to standard Starlink satellites using a small subset of observations.
• Identified and quantified flaring events by measuring peak brightness relative to normal levels.
• Used statistical analysis to estimate uncertainty in brightness differences, particularly for DarkSat.

Experimental results

Research questions

• RQ1 What is the average visual magnitude of Starlink satellites at 550 km altitude before the VisorSat design?
• RQ2 How much fainter is the DarkSat variant compared to standard Starlink satellites?
• RQ3 What is the frequency and magnitude of flaring events observed in Starlink satellites?
• RQ4 To what extent do observational uncertainties affect brightness comparisons between satellite variants?
• RQ5 How do these pre-VisorSat measurements serve as a baseline for evaluating future satellite brightness reduction strategies?

Key findings

• The mean visual magnitude of Starlink satellites at 550 km altitude is 4.63 with a standard error of ±0.02.
• DarkSat is approximately 1.6 magnitudes fainter than standard Starlink satellites, corresponding to a 78% reduction in brightness.
• The brightness difference between DarkSat and standard satellites has a high uncertainty due to the small number of observations.
• Some Starlink satellites exhibited flares up to 10,000 times their normal brightness, indicating significant transient brightness variations.
• The dataset provides a critical pre-VisorSat baseline for assessing the effectiveness of future brightness reduction designs.
• The results confirm that satellite brightness varies significantly over time and depends on orientation and surface properties.