The planned launch of 500,000 satellites could render the Hubble Space Telescope obsolete, according to a recent study. Simulations indicate that satellite streaks could mar approximately one-third of Hubble's images, even when the telescope remains above Earth's weather. A team of researchers modeled plans to launch around 560,000 satellites by the 2030s. Led by Dr. Alejandro S. Borlaff at NASA's Ames Research Center, the team studies satellite light interference with telescope observations and develops tools to protect limited observing time. Dr. Borlaff notes that space telescopes typically operate in pristine environments. With 15,000 satellites already in Earth's orbit, the researchers modeled how proposed fleets could further congest the skies. These projections rely on legal filings describing planned orbital shells around the planet. While not all plans materialize, the filing totals indicate the upper limit telescopes must plan for. Satellite streaks occur when sunlight reflects off moving spacecraft, creating bright lines during camera exposure. Even when the line misses the science target, stray light can raise the background, making faint details harder to measure. Space telescopes avoid clouds and city glow, but many share low-Earth orbit, the band up to about 1,200 miles high. The Hubble test revealed that about 4.3% of images contained at least one satellite trail. The team's model accurately predicts today's orbit crowding, suggesting future challenges. A telescope's field of view strongly influences satellite crossing frequency. An average Hubble image had two trails, while Xuntian's wider view saw around 90. Broad-view survey missions would see streaks in nearly all exposures unless satellite designs and orbits change. The key concern is surface brightness because faint streaks can contaminate careful measurements. Sunlit satellites create the sharpest streaks, overwhelming the dim features survey telescopes map. Predicting streak brightness is difficult due to companies' reluctance to share full shape and coating details. Space observatories collect long exposures for faint galaxies, dark matter maps, and chemical clues in distant nebulae. If a streak spoils a rare observation, astronomers may lose their only opportunity, especially for fleeting events that fade within hours. Teams already correct for cosmic rays and detector defects, but satellite trails add structured noise harder to mask. Mitigation is complex. Satellite builders can use darker materials or sunshades, but even small reflective panels can leave bright marks. An orientation that appears dim from the ground can expose a larger surface to an orbiting telescope, depending on the Sun's angle. As satellites age or fail, uncontrolled tumbling can cause sudden bright flares that slip past prediction software. Hubble and satellite streaks require accurate positions, but many public trackers rely on basic orbit data. For low-orbit observatories, researchers argue that position accuracy must be measured in inches, not miles, to flag a streak. This precision would require satellite operators to share better orbit updates and a public archive. Some missions impose strict pointing constraints to avoid Earth glare and reduce streak risk, but these limits shrink available science time and can leave sky coverage gaps. Shorter exposures reduce crossing chances but force more repeats and data handling. A 2020 report urges satellite operators to reduce brightness and coordinate closely with observatories. Astronomy teams can mask streaked pixels, but this adds processing time and complexity. Some observatories use prediction software to time exposures, but crowded orbits make clean windows rare. Shared models of satellite light reflection are needed for accurate corrections. Satellite internet offers fast connections to remote regions, creating a trade-off between tangible services and astronomers' need for clear skies. Markets will determine the survival of satellite systems, but telescopes cannot risk decades-long missions requiring stable conditions. Near-Earth space is a shared resource, and decisions made this decade will shape future observatories' capabilities. The study is published in the journal Nature.
