Concerns about ground based astronomical observations: a step to safeguard the astronomical sky (2001.10952v2)

Abstract: This article aims to highlight the impact for ground based astronomical observations in different windows of the electromagnetic spectrum coming from the deployment of fleets of telecommunications satellites. A particular attention is given to the problem of crowding of circumterrestrial space by medium/small size orbiting objects. Depending on their altitude and surface reflectivity, their contribution to the sky brightness is not negligible for professional ground based observations. With the huge amount of about 50,000 new artificial satellites for telecommunications planned to be launched in Medium and Low Earth Orbit, the mean density of artificial objects will be of >1 satellite for square sky degree; this will inevitably harm professional astronomical images leaving trails on them. Only one of these project, Starlink@SpaceX's, authorized by US Federal Communication Commission, plans to deploy about 42,000 not geostationary satellites, which will shine in sky after sunset and before sun dawn. Satellites will be observed in deep field images and particularly negative for scientific large area images used to search for Near Earth Objects, predicting and, eventually, avoiding possible impact events. Serious concerns are also common to other wavelengths eligible for ground based investigation, in particular for radio-astronomy, whose detectors are already saturated by the ubiquitous irradiation of satellites communication from Space stations as well as from the ground. The risk of running into the "Kessler syndrome" is also noteworthy. Understanding the risk for astronomical community, a set of actions are proposed in this paper to mitigate and contain the most dangerous effects arising from such changes in the population of small satellites. A dedicate strategy for urgent intervention to safeguard and protect each astronomical band observable from the ground is outlined.

• The paper finds that over 50,000 LEO telecommunication satellites can substantially interfere with astronomical imaging through increased brightness and radio frequency impacts.
• It applies analytical assessments on optical and radio data, highlighting significant interference from major projects like Starlink.
• The study advocates for international cooperation, advanced technological solutions, and regulatory measures to mitigate the negative effects on ground-based astronomy.

Impact of Telecommunications Satellite Constellations on Ground-Based Astronomy

The increasing deployment of telecommunications satellite constellations poses significant challenges to ground-based astronomical observations. This paper primarily focuses on the implications of over 50,000 satellites planned for Medium and Low Earth Orbit (LEO), highlighting the potential adverse effects on various electromagnetic spectrum observations. The issue is predominantly centered around increased sky brightness and interference in observational data, marking a shift in the landscape of astronomic imaging and signaling the necessity for mitigation strategies.

Key Concerns:

1. Electromagnetic Interference: The sheer volume of LEO satellites, primarily from projects like Starlink which plans around 42,000 satellites itself, translates to an average density exceeding one satellite per square degree of the sky. Their brightness, estimated to range from the 3rd to 7th magnitude during twilight periods, poses a substantial threat to imaging for sky surveys, Near Earth Object (NEO) detection, and other critical astronomical tasks.
2. Radio Astronomy Vulnerabilities: Beyond the optical bands, radio astronomers face significant risks with communication frequencies overlapping with those essential for radio observations. The inevitable saturation from radio transmissions of telecommunication satellites directly compromises the effectiveness of ground-based radio telescopes in bands crucial for scientific inquiry.
3. Potential for Kessler Syndrome: The paper also draws attention to the non-negligible risk of contributing to the Kessler syndrome, a scenario where the density of objects in low Earth orbit is high enough to potentially trigger collisions, creating cascading space debris and subsequent operational hazards for both present and future space endeavors.

Mitigation Strategies:

The authors propose an array of countermeasures to mitigate the impacts on astronomical observations. Strategies emphasize the necessity of international cooperation, involving stringent regulation and deployment moderation of satellite constellations. The paper insists on a symbiotic relationship between satellite operators and the astronomical community to alleviate predictable impacts through:

• Technological innovations to reduce satellite reflectivity.
• Stringent guidelines ensuring minimal interference with astronomical frequencies.
• Temporal and spatial management of satellite orbits to avoid critical observation windows.

Implications and Future Directions:

The implications of this research are profound, insisting on immediate and coordinated action to preserve the integrity of astronomical observations. As the reliance on satellite communications grows, particularly for internet access in underserved regions, balancing this demand with the preservation of astronomical heritage and scientific capacity becomes vital. The call for international governance highlights an urgent need for a cohesive framework that addresses both the looming saturation of LEO and the long-term viability of ground-based astronomy.

Moving forward, the paper advocates enhancing legislation and international agreements to ensure the protection of the night sky as part of our cultural and scientific heritage. The engagement of global astronomical organizations, alongside technological advancements tailored to reduce satellite-induced interruptions, offers a pathway to sustain the symbiosis between terrestrial and space-based technology and the quest for astronomical discovery.

The dialogue on the protection of observational astronomy against technological progress initiated by this paper provides a critical foundation for future deliberations, determining how we balance human technological advancement with environmental and scientific stewardship.