Astronomers for Planet Earth (A4E) is an international grassroots movement of astronomy students, educators, amateurs and scientists, working to address the climate crisis from an astronomical perspective. The network consists of more than 2,000 astronomers distributed over 85 countries and was born out of a common concern for the impact of astronomical research on the climate. Our mission is to address the climate crisis through public education as well as advocating for changes in how we carry out our research.  

As astronomers, we recognize that we do not have exclusive rights to dark skies nor to near-Earth space, as both are a common resource and source of inspiration to all humanity. It is with this recognition that we believe that we have a duty to protect both, ensuring that our activities do not limit or deny others the opportunity to enjoy and benefit from these resources. It is also paramount, given the climate crisis, that our use of these resources do not have a negative impact on the climate.

While we recognize the benefits of telecom satellites, we are gravely concerned by the recent proliferation of very large satellite constellations that are currently being deployed in low-Earth orbit (LEO), and even more concerned with some of the new constellations being proposed for the future. In particular, both Reflect Orbital and SpaceX have recently submitted proposals to the U.S. Federal Communications Commission (FCC) toward the deployment of new satellite constellations. 

Reflect Orbital has announced its intention to deploy a constellation of up to 50,000 satellites by 2035¹ specifically designed to provide artificial illumination at night using sunlight reflected from an array of large satellites in orbit. If realized, this constellation will contribute further to the endemic problem of light-pollution which not only denies people the ability to enjoy dark skies, but puts nocturnal species at risk by destroying their natural habitat, as well as having a negative impact on human health by altering our natural sleep patterns².  

Meanwhile, SpaceX is proposing a new constellation of 1 million satellites to serve as a distributed data center in space. This proposal is more than an order of magnitude larger than their already approved Starlink constellation currently being deployed. In particular, a significant fraction of this proposed constellation will be constituted of satellites in a Sun-synchronous orbit ensuring that they are constantly illuminated.

Both of these constellations will limit the research capacity of astronomical facilities on the ground and in space^3,4, and will potentially alter the view of the night sky for humans on a global scale.

The potential benefits of any large satellite constellation should be weighed against the potential damage that it may cause, particularly to the atmosphere and the climate. As satellites in low-Earth orbit have short lifetimes of 5 to 10 years, deployment of such a large satellite constellation requires an elevated frequency of launches to be completed within that same time frame. To maintain such a constellation likewise requires that launches continue at a rapid pace to replace the satellites falling back into the atmosphere. The deposition of large quantities of metals in the upper atmosphere from infalling satellites poses a novel threat to the environment on a global scale^5,6, while the high frequency of launches will further exacerbate our negative impact on the climate^7,8. We believe that such large constellations in LEO represent an unsustainable approach for providing services that could be provided by other means. 

Comprehensive scientific evidence clearly demonstrates that we are living in a climate emergency that calls for urgent action^9,10. We therefore stand firmly against both projects, as they not only threaten our profession as astronomers, but also pose a grave and irreversible risk to dark skies, biodiversity, and human health. We urge the FCC to reject both proposals, or, at the very least, to require a full environmental impact assessment from these and any other future proposals for large constellations in low-Earth orbit before being approved. 

Bibliography

1. https://www.reflectorbital.com/
2. DarkSky International “State Of The Science” report for 2025, https://doi.org/10.5281/zenodo.15492392
3. Borlaff, A.S., Marcum, P.M., Howell, S.B. Satellite megaconstellations will threaten space-based astronomy. Nature 648, 51–57 (2025). https://doi.org/10.1038/s41586-025-09759-5
4. Kocifaj, M.,Kundracik F., Wallner S., Low Earth Orbit satellite fragmentation rates are critically disrupting the natural night sky background, Monthly Notices of the Royal Astronomical Society: Letters, Volume 541, Issue 1, July 2025, Pages L47–L51, https://doi.org/10.1093/mnrasl/slaf052 
5. Maloney, C. M., Portmann, R. W., Ross, M. N., & Rosenlof, K. H. (2025). Investigating the Potential Atmospheric Accumulation and Radiative Impact of the Coming Increase in Satellite Reentry Frequency. Journal of Geophysical Research: Atmospheres, 130(6).https://doi.org/10.1029/2024jd042442 
6. Ferreira, J. P., Huang, Z., Nomura, K., & Wang, J. (2024). Potential Ozone Depletion From Satellite Demise During Atmospheric Reentry in the Era of Mega‐Constellations. Geophysical Research Letters, 51(11).https://doi.org/10.1029/2024gl109280  
7. Revell, L.E., Bannister, M.T., Brown, T.F.M. et al. Near-future rocket launches could slow ozone recovery. npj Clim Atmos Sci 8, 212 (2025). https://doi.org/10.1038/s41612-025-01098-6 
8. Ryan, R.G., Marais, E.A., Balhatchet, C.J., Eastham, S.D. Impact of Rocket Launch and Space Debris Air Pollutant Emissions on Stratospheric Ozone and Global Climate. Earths Future. 2022 Jun;10(6):e2021EF002612. https://doi.org/10.1029/2021EF002612 
9. Global Warming of 1.5°C. An IPCC Special Report; Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)  https://www.ipcc.ch/sr15/
10. Lenton, T.M., Rockström, J., Gaffney, O., et al. Climate tipping points – Too risky to bet against. Nature 575, 592-595 (2019) https://doi.org/10.1038/d41586-019-03595-0