For Policy Makers

Astronomy has revolutionized the way we think about our universe and our place within it. As our society changes, so too does the way we interact with our night sky and broader universe. Our skies belong to everyone, and of course we must share it. However, as our technology advances, it is imperative then that we take the steps necessary to protect astronomy from the many threats to the field it sees today.

Artificial Light at Night

Future astronomical discoveries depend upon dark and quiet skies, but not only astronomy is impacted by the rise of artificial light at night (ALAN). Rapidly growing ground based light pollution around the globe also significantly threatens human health, the environment, and food production. 

Recent studies show an average 10% year-to-year increase in sky brightness in North America, and remote sites are increasingly impacted by artificial light at night. Globally we spend at least $50 billion on energy costs each year to produce light that escapes into space. With the increase of ALAN, we see disruption in seasonal crop growing season and production, and impacts to human health such as depression, obesity, sleep disorders, and cancer risk. We also see ecological issues with implications for plant and pollinator reproductive cycles, foraging and feeding habits, migration and navigation issues, and many other impacts across all taxonomic kingdoms. Glare from blue LEDs can also cause road traffic and industrial hazards

The International Astronomical Union recommends sky brightness levels to be less than 10% above naturally accusing airglow to protect astronomical observatories. However, only one observatory in the continental US meets this criterion: The University of Texas McDonald Observatory. Actions mitigating the many threats posed by artificial light at night are needed. We must treat light pollution as the environmental issue that it is.

What can be done?

  • Adopt lighting zoning (e.g., the city of Flagstaff, the world’s first Dark Sky Community). A good starting point is the 5 Principles for Responsible Outdoor Lighting, guidelines set forth by Dark Sky International
  • Use nighttime friendly lighting: full shielding, no brighter than needed, active controls, and warm colors with minimum blue emission.
  • Limit artificial lighting at night via lumens per developed acre or lumens per fixture limitations

Issue summary: “Threats to Dark and Quiet Skies by Artificial Light At Night”

Radio Frequency Interference

Signals from Radio Frequency Interference (RFI) are often much stronger than celestial sources, and they can have a range of effects on radio astronomy from data loss to hardware damage.

The radio spectrum is heavily regulated to enable many uses while limiting interference. In the US, the Federal Communication Commission (FCC) regulates the radio spectrum. The radio spectrum is divided into frequency bands assigned to particular uses with a series of associated rules. Most spectrum bands are shared among several active services, but some bands are shared only among passive services. An important current use is by Earth-observing satellites that provide important environmental data.

To mitigate the impacts of RFI on ground-based astronomy, astronomers employ various measures. For the most part, astronomers can track the location of satellite signals. Although astronomers know the frequencies and locations of most transmitters, which can help them to devise strategies to mitigate harmful interference, this is not a panacea. Radio astronomers must work together with satellite operators to mitigate impacts on radio telescopes.

 

Geographic isolation is the most effective means of reducing RFI from terrestrial radio communications. Radio Quiet Zones (RQZs) are remote areas where use of radio spectrum is legally restricted to benefit radio astronomy. More than a dozen RQZs have been created worldwide. Unfortunately, RQZs are not yet recognized internationally, so protection from satellite and airplane signals is not guaranteed.

What can be done?

  • Support efforts to increase regulatory protection of radio astronomy sites.
  • Encourage and support satellite operators and industry to collaborate with the astronomy community to develop, share, and adopt best practices in interference mitigation, leading to widely adopted standards and guidelines.
  • Collaborate with telecommunications companies, satellite operators, and regulatory bodies to mitigate impacts on observatories. 
  • Encouraging responsible use of wireless technologies and promoting cooperation in minimizing RFI sources can contribute to effective long-term mitigation.

 

Issue summary: “Threats to Dark and Quiet Skies by Radio Frequency Interference”

Large Satellite Constellations

All ground-based optical, infrared, and radio observatories are affected by the recent massive proliferation of commercial satellites in low Earth orbit.

As of 2024, there are more than 6,300 satellites from large constellations in low Earth orbit (LEO) — 81% of all active satellites launched in the last four years. Recent filings with the International Telecommunication Union suggest a dramatic increase of possibly hundreds of thousands of satellites in LEO in the coming decade. This increases collision risk and the possibility of rendering LEO unusable to all without careful management. 

Satellites and orbital debris reflect sunlight, leaving streaks across science images. Satellite radio transmissions interfere with radio telescopes as they pass overhead. The combined effect of current satellites in orbit and the accumulation of space debris may already be causing an approximately 10% increase in the brightness of the night sky compared to natural levels. There may be additional interference to astronomy from larger structures in space including space-based solar power systems, LEO space habitats, and larger satellites that connect directly to mobile phone handsets. The changing visual appearance of the sky impacts our shared cultural heritage and environment as well.

The growth of LEO satellites has a direct impact on professional and amateur astronomy, and without appropriate mitigations, it will have a significant and detrimental effect on the dark and quiet sky across the globe, even rendering some observations impossible.

US regulations and guidelines do not consider optical astronomy in licensing and inadequately consider radio astronomy. The AAS is working to collaborate with satellite operators, but harm mitigation has largely been voluntary. Mitigation of harm to astronomy should be a requirement of licensing.

What can be done?

  • Provide incentive measures for the space industry to develop the required technology to minimize negative impacts.
  • Support the establishment of test labs for brightness and basic research into alternate less reflective materials and reduction of unwanted radiation in the radio regime for spacecraft manufacturing.
  • Increase financial support for astronomy to offset and compensate the impacts on observatory operations and implement mitigation measures at observatories and in software. 
  • In the longer term, establish regulations and conditions of authorization and supervision based on practical experience as well as the general provisions of international law and main principles of environmental law to codify industry best practices that mitigate the negative impacts on astronomical observations. Satellites in LEO should be designed and operated in ways that minimize adverse effects on astronomy and the dark and quiet sky.
  • Continue to support finding solutions to space sustainability issues, including the problem of increasing space debris leading to a brighter sky. Minimizing the production of space debris will benefit not only the field of astronomy but all sky observers worldwide.

Issue summary: “Threats to Dark and Quiet Skies by Satellite Constellations”