The Low Earth Orbit Satellite Population and Impacts of the SpaceX Starlink Constellation (2003.07446v2)

Abstract: I discuss the current low Earth orbit artificial satellite population and show that the proposed `megaconstellation' of circa 12,000 Starlink internet satellites would dominate the lower part of Earth orbit, below 600 km, with a latitude-dependent areal number density of between 0.005 and 0.01 objects per square degree at airmass < 2. Such large, low altitude satellites appear visually bright to ground observers, and the initial Starlinks are naked eye objects. I model the expected number of illuminated satellites as a function of latitude, time of year, and time of night and summarize the range of possible consequences for ground-based astronomy. In winter at lower latitudes typical of major observatories, the satellites will not be illuminated for six hours in the middle of the night. However, at low elevations near twilight at intermediate latitudes (45-55 deg, e.g. much of Europe) hundreds of satellites may be visible at once to naked-eye observers at dark sites.

• The paper analyzes the rapidly growing population of Low Earth Orbit (LEO) satellites, focusing on the significant impact and projected dominance of the SpaceX Starlink megaconstellation.
• It quantifies the potential density of Starlink satellites and calculates their visibility, highlighting significant interference risks for ground-based astronomical observations, especially at twilight.
• The study provides numerical data on current satellite counts, projects substantial increases due to Starlink (4x-20x), and discusses initial observations of satellite brightness and partial success of mitigation efforts like 'Darksat'.

Overview of "The Low Earth Orbit Satellite Population and Impacts of the SpaceX Starlink Constellation"

This paper by Jonathan C. McDowell offers a comprehensive analysis of the evolving landscape of low Earth orbit (LEO) satellites, with a particular focus on the significant contributions of the Starlink "megaconstellation" by SpaceX. LEO, defined as altitudes below 2,000 km, is increasingly becoming crowded with artificial satellites, and the deployment of networks like Starlink is transforming this environment.

Starlink's Presence in LEO

The introduction of Starlink, a proposed constellation of approximately 12,000 satellites, is set to dominate LEO, especially below 600 km. McDowell's paper highlights that the density of these satellites could reach between 0.005 and 0.01 objects per square degree, significantly affecting sky visibility. The planes of the satellites' orbits are organized such that, from certain latitudes, hundreds could be visible at any given moment, particularly at twilight.

Impact on Observational Astronomy

One of the key issues discussed is the effect on ground-based astronomical observation. The paper calculates that during ideal viewing conditions at certain latitudes and times of the year, a vast number of Starlink satellites could be visible simultaneously. For example, in Northern Latitudes, up to 200 satellites could be present near the horizon during twilight, causing potential disruptions to observational data, particularly in long exposure and twilight observations.

Numerical Findings and Demographics

The paper presents detailed statistical data on the current satellite population. As of March 2020, there were over 11,000 tracked objects in upper LEO and approximately 688 in lower LEO with masses greater than 100 kg. The Starlink constellation has contributed significantly to the surge in the satellite population within the lower LEO segment. Projections suggest that Starlink will lead to an increase by factors of 4 to 20, radically affecting naked-eye object counts.

Observational Analysis

Initial observational campaigns reported the magnitudes of Starlink satellites to typically range from 3 to 7, confirming many are visible to the naked eye under dark skies. Innovations such as creating "Darksat," with dark coatings to reduce brightness, have shown only partial success, reducing visibility by roughly one magnitude.

Long-term Implications

The Starlink constellation, alongside other proposed satellite networks, represents a significant shift in the anthropogenic enhancement of the LEO environment. While these satellites support global telecommunications infrastructure, they also pose challenging new variables for astronomers.

Future Considerations

The paper emphasizes the need for continued monitoring and potential mitigation strategies to address the light pollution and observational interference caused by these satellites. Adjustments to satellite designs, such as improved Albedo controls, alongside policy frameworks for future satellite deployments, may become critical areas for ensuring the balance between technological advancement and the preservation of astronomical heritage and research.

The paper serves as a pivotal reference for understanding the current and future dynamics of satellite populations in LEO and their implications for astronomy and satellite operations.