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SpaceX is working to make its satellites less annoying to astronomers by testing ways to prevent Starlink from appearing in images of the cosmos. The company recently lowered the altitude of a batch of its Internet satellites to mitigate their brightness as seen from Earth.
in a letter According to the Federal Communications Commission (FCC), SpaceX revealed that it began 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 a success, resulting in a nearly 60% reduction in sunlit satellites appearing in images captured by the Vera Rubin Observatory, a telescope in Chile.
Low Earth orbit is increasingly crowded with satellites, most of which belong to SpaceX. There are currently 6,912 Starlink satellites in orbit, located approximately 342 miles (550 kilometers) above the Earth’s surface. Orbiting satellites add unwanted noise to observations of the night skies by reflecting sunlight, appearing as streaks in images captured by ground-based observatories. The first Starlink satellites were very 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 next-generation Starlink satellites, which are larger and brighter than their predecessors. The first-generation Starlinks weigh about 573 pounds (260 kilograms), but future versions are much larger, 2,755 pounds (1,250 kg), and are therefore estimated to be about one magnitude brighter than the OG satellites.
SpaceX is collaborating with the National Science Foundation (NSF) to reduce the impact of its next-generation satellites on optical astronomy. The company recently reduced the altitude of its Starlinks demonstration to 217 miles (350 km) above the Earth’s surface, reducing its ability to capture and reflect sunlight.
“SpaceX’s analysis also demonstrates that the maximum brightness of nadir surfaces increases only marginally when operating at 350 km (217 miles), due to higher eclipse fraction and angular velocity,” the company wrote in its letter. In other words, SpaceX says the satellites’ reflective brightness, seen from below, doesn’t increase much at lower altitudes because they spend more time in Earth’s shadow and move faster across the sky.
The NSF agrees that this strategy could help. Lower orbits could “be beneficial for ground-based optical and infrared astronomy, as satellites move faster through a telescope’s focal plane and are more out of focus, reducing overall brightness per pixel,” a spokesperson said. from the NSF to Gizmodo in an email. “At lower altitudes, the Earth also blocks sunlight from satellites for longer periods of the night, without reflecting back to the ground.” This allows the satellites to remain dimmer than about 7th magnitude (the threshold of naked-eye visibility) for much of the night, the spokesperson explained.
There have been previous attempts to diminish Starlink’s effect on astronomical observations. SpaceX has been working with the International Astronomical Union and its Center for the Protection of the Dark and Quiet Sky from Interference from Satellite Constellations, to find the main source of its satellites’ reflectivity and develop strategies to mitigate it. As a result, the company changed the orientation of the satellites and their solar panels, and installed visors to reduce their brightness.
This recent modification of satellite orbits is still being evaluated as it may have some drawbacks. “There are trade-offs: Satellites at lower altitudes may be brighter during twilight and impact science that requires twilight observations, such as studies of near-Earth objects,” NSF added. The foundation will continue to work with SpaceX over the next year to verify whether the mitigation is working as planned.
It’s not just SpaceX launching satellites into orbit, and the growing amount of hardware saturating Earth’s orbit could further obscure our view of the cosmos unless more companies commit to reducing their interference with astronomy.
