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According to Universe Today and a pre-print by researchers from NASA Ames, satellites left trails in 73.3% of SPHEREx images between May and September 2025; simulations indicate that, with proposed large constellations, contamination could reach 100% of the exposures of NASA’s space telescope in low Earth orbit.
The satellites in low Earth orbit no longer only affect ground-based observatories. A new study cited by Universe Today shows that NASA’s SPHEREx space telescope had 73.3% of its images contaminated by at least one artificial satellite trail between May and September 2025.
This finding is noteworthy because SPHEREx is also in space, about 700 km above the Earth’s surface. Even so, according to the pre-print by researchers affiliated with the NASA Ames Research Center, luminous trails frequently appear in the exposures and could worsen if megaconstellations with hundreds of thousands or millions of objects advance in low orbit.
NASA Telescope was hit in full low orbit
SPHEREx, short for Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer, was designed to map the entire sky in near-infrared light. NASA describes the mission as a spectral survey capable of observing hundreds of millions of galaxies and stars.
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This type of observation requires wide sky coverage and sensitive exposures. The same design that allows mapping the universe also makes the telescope vulnerable to bright satellites crossing its field of view. The problem, previously associated mainly with ground-based telescopes, now appears within the orbit itself.
Trails appeared in 73.3% of the images
The study analyzed images collected by SPHEREx between May and September 2025. The result was that 73.3% of the exposures already showed contamination by at least one artificial satellite trail.
On average, researchers found 2.18 trails per exposure. The observed pattern concentrates in a kind of “X,” following trajectories associated with the orbits of satellite megaconstellations. This indicates that the problem is not random: it follows the geometry of the objects launched around the Earth.
Images gain marks similar to tracks
The Universe Today report describes a visual effect called by the authors as “railroad tracks.” The very bright center of the trail can be erased by automatic systems, but parallel lines remain imprinted on the scientific image.
This detail is important because it’s not just an ugly stain on a photo. When a trail passes over an astronomical source, the photometric data hidden under that mark can be lost. The image continues to exist, but part of the scientific information becomes unrecoverable.
System created against cosmic rays is also triggered
The SPHEREx uses an automated algorithm called sample up-the-ramp to protect itself from sudden events, like cosmic rays hitting detector pixels. When there is an unexpected energy spike, the system stops collecting at that pixel to avoid saturation.
The problem is that very bright commercial satellites can also trigger this mechanism. Thus, a feature created to protect data against natural interferences ends up reacting to artificial light pollution caused by objects in orbit.
Hubble has also felt the advance of satellites
The SPHEREx is not the only space telescope affected. Universe Today recalls a previous study led by Sandor Kruk, which identified an increase in the fraction of Hubble images crossed by satellites.
According to this research cited in the report, contamination in Hubble images rose from 2.8% in the early 2000s to 5.9% in 2021. The comparison needs to be made cautiously because Hubble does not photograph such wide swaths of the sky as SPHEREx. Even so, the warning sign is clear.
Megaconstellations increase pressure on astronomy
The advance of megaconstellations makes the scenario more difficult. Communication satellites, internet, direct connection with cell phones, and new infrastructures in orbit can greatly increase the number of objects crossing the sky observed by scientific instruments.
Some companies have tested dark coatings and screens to reduce glare. However, according to Universe Today, new larger systems may negate some of this benefit. If satellites become larger, more numerous, and more reflective, the sky becomes an increasingly less clean environment for astronomical observation.
Extreme scenario may contaminate all images
The report cites recent requests submitted to the FCC in the United States, which could allow up to 2 million satellites in low orbit. This number contrasts with the current population of orbital objects, which is much smaller, and appears as a warning scenario.
According to the simulations mentioned in the study, if these projects are approved and launched, 100% of SPHEREx images could be contaminated by satellite trails. The projected average would reach 189 trails per exposure, a huge jump from the 2.18 trails observed during the analyzed period.
Problem is not limited to pretty space photos
For the general public, satellite trails may seem like just streaks in photographs. For science, however, the consequence is deeper. Space telescopes measure brightness, color, position, and spectrum of very distant objects, and any contamination can affect these measurements.
The SPHEREx was planned to answer questions about the history of the universe, the epoch of reionization, and the distribution of ice and molecules in our galaxy. When satellites cross the images, they can reduce the quality of the data used to investigate topics that go far beyond the appearance of the sky.
Lack of international agreement worries researchers
Groups linked to astronomy have been warning for years about the impacts of megaconstellations. The problem involves private companies, national regulatory agencies, commercial interests, global connectivity, and the preservation of the sky as a scientific resource.
So far, according to the report, there is no international agreement capable of broadly containing or organizing the problem. The concern is that decisions made by a few countries and companies could alter the capacity to observe the sky for the entire global scientific community.
Modern sky enters silent dispute
The case of SPHEREx shows that orbital light pollution is no longer a distant problem. Even space telescopes, positioned above the atmosphere, already face satellite trails in a large part of the images.
The question now is to decide how far low Earth orbit can be occupied without compromising astronomy. Do you think the advancement of satellites for internet and communication justifies this impact on telescopes, or should there be an international limit to protect the scientific sky? Leave your opinion in the comments.
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