Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
SpaceX is working to make its satellites less annoying for astronomers, 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 at the Federal Communications Commission (FCC), SpaceX revealed that it has begun operating 300 of its satellites at a lower orbital altitude as part of the company’s efforts to reduce the impact of Starlink on the optical astronomy. The company claims that the new method has been a success, resulting in a reduction of almost 60% of the satellites illuminated by the sun that appear in the images captured by the Vera Rubin Observatory, a telescope in Chile.
The low Earth orbit has become more and more 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 sky by reflecting sunlight, which appear as streaks in images captured by ground-based observers. 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 gave SpaceX approval to launch up to 7,500 next generation Starlink satelliteswhich are bigger and brighter than their predecessors. First-generation Starlinks weigh about 573 pounds (260 kilograms), but future versions are much larger at 2,755 pounds (1,250 kilograms) and are therefore estimated to be about a full 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 demo to 217 miles (350 km) above the Earth’s surface, which reduces its ability to capture and reflect sunlight.
“SpaceX’s analysis also shows that the maximum brightness from the nadir surfaces is only marginally increased when operating at 350 km (217 miles), due to a higher eclipse fraction and angular rate,” the company said. written in his letter. In other words, SpaceX says that the reflected brightness of the satellites, seen directly from below, does not increase much at lower altitudes because they spend more time in the shadow of the Earth and move faster in the sky.
The NSF agrees that this strategy could help. The lower orbits could “be beneficial for ground-based optical and infrared astronomy, as satellites move faster through the focal plane of a telescope and are more diffuse, reducing the overall brightness per pixel,” a spokesman of NSF told Gizmodo in an email. “At lower altitudes, satellites are also blocked from sunlight from Earth for longer portions of the night, not reflecting back to earth.” This allows the satellites to remain dimmer than about 7th magnitude – the threshold for visibility to the naked eye – for most of the night, the spokesman explained.
There have been previous attempts to diminish the effect of Starlink on astronomical observations. SpaceX has been working with the International Astronomical Union, and its Center for the Protection of Dark and Silent Skies from Satellite Constellation Interference, to find the main source of the reflectivity of 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 visors to reduce their brightness.
This recent modification to the orbits of the satellites is still being evaluated because it may have some drawbacks. “There are trade-offs, satellites at lower altitudes can be brighter at dusk and impact science that requires twilight observations, such as surveys of near-Earth objects,” added NSF. The foundation will continue to work with SpaceX next year to verify whether the mitigation is working as planned.
SpaceX isn’t the only one launching satellites into orbit, and the growing amount of hardware cluttering Earth’s orbit could further obscure our view of the cosmos unless more companies work to reduce their interference with astronomy.
