ESO Study Finds That No More Than 100,000 Satellites Should Orbit Earth

Key Points:

• A pioneering study by the European Southern Observatory (ESO) recommends limiting the total number of satellites in Earth's orbit to 100,000 that are faint enough to be invisible to the naked eye from dark sites, to protect astronomical observations.
• With over 14,000 satellites currently orbiting Earth and proposals from companies like SpaceX and Reflect Orbital to launch up to 1.7 million more, bright satellite constellations are increasingly interfering with telescope images by creating bright streaks that obscure cosmic targets.
• Simulations show that SpaceX's planned megaconstellation could cause up to 28% loss in field-of-view for ESO’s Very Large Telescope images, while Reflect Orbital's proposed in-space mirrors could render images from the Vera C. Rubin Observatory unusable.
• The study emphasizes that if satellites are brighter than the proposed magnitude 7 threshold for naked-eye visibility, the acceptable number of satellites must be significantly lower to avoid severe impacts on optical astronomy.
• Both SpaceX and Reflect Orbital await Federal Communications Commission (FCC) approval for their satellite plans, with ESO urging regulators to consider the existential threat these constellations pose to astronomy.