SpaceX is testing low satellite orbits to prevent Starlink from ruining telescope images

SpaceX is working to make its satellites less annoying to astronomers by testing ways to prevent Starlink from showing up in images of the universe. The company recently lowered the height of a group of its Internet satellites to mitigate their brightness as seen from Earth.

In a letter SpaceX has revealed to the Federal Communications Commission (FCC) that it has begun operating 300 of its satellites at a lower orbital altitude as part of the company’s efforts to reduce Starlink’s impact on optical astronomy. The company claims that the new method has been successful, reducing the appearance of sunlit satellites by approximately 60% in images captured by the Vera Rubin Observatory, a telescope in Chile.

Low Earth orbit is increasingly filled with satellites, most of which belong to SpaceX. There are currently 6,912 Starlink satellites in orbit, located about 342 miles (550 kilometers) above the Earth’s surface. Orbiting satellites add unwanted noise to observations of the night sky by reflecting sunlight, which appears as streaks in images taken by ground-based observatories. The first Starlink satellites were extremely bright, making them visible to the naked eye and saturating the lenses of telescopes pointed in their direction.

In December 2022, the FCC granted SpaceX approval to launch up to 7,500 vehicles. The next generation of Starlink satelliteswhich is larger and brighter than its predecessors. First-generation Starlinks weighed about 573 pounds (260 kg), but future versions are much larger at 2,755 pounds (1,250 kg) and are therefore estimated to be a full magnitude brighter than the OG satellites.

SpaceX is collaborating with the National Science Foundation (NSF) to reduce the impact of next-generation satellites on optical astronomy. The company recently lowered the altitude of its experimental Starlinks to 217 miles (350 km) above the Earth’s surface, reducing their ability to capture and reflect sunlight.

“SpaceX’s analysis also shows that peak brightness from isotopic surfaces increases only slightly when operating at a distance of 350 kilometers (217 miles), due to the higher eclipse and angular ratio,” the company wrote in its letter. In other words, SpaceX says the satellites’ reflective brightness, as seen from directly below, doesn’t increase much at lower altitudes because they spend more time in Earth’s shadow and move faster across the sky.

The NRF agrees that this strategy can help. An NSF spokesperson told Gizmodo in an email that low orbits “can be useful for ground-based optical and infrared astronomy, as satellites move faster through the telescope’s focal plane and are out of focus, reducing the overall brightness of each pixel.” . “At lower altitudes, satellites are also blocked from sunlight by Earth for longer parts of the night, and are not reflected back toward Earth.” The spokesman explained that this allows the satellites to remain less bright than approximately seventh magnitude – the threshold for visibility with the naked eye – throughout most of the night.

There have been previous attempts to reduce Starlink’s impact on astronomical observations. SpaceX is working with the International Astronomical Union, and its Center for the Protection of Dark and Quiet Skies from Satellite Constellation Interference, to find the main source of the reflection from its satellites and develop strategies to mitigate it. As a result, the company changed the orientation of the satellites and their solar panels, and installed masks to reduce their brightness.

This latest modification to satellite orbits is still under evaluation because it may have some drawbacks. “There are trade-offs: satellites at lower altitudes may be brighter at twilight, and impact science requires twilight observations, such as Near-Earth Object surveys,” NSF added. The organization will continue to work with SpaceX over the next year to verify whether the mitigation process is working as intended.

Not only is SpaceX launching satellites into orbit, but the increasing amount of hardware cluttering Earth’s orbit could further obscure our view of the universe unless more companies commit to reducing their interference in astronomy.