SpaceX is making efforts to make its satellites less interfering with astronomical observations. To do this, the company is testing new ways to reduce the brightness of Starlink in space images. In particular, SpaceX recently lowered the orbital altitude from 550 kilometers to 350 kilometers of some Internet satellites to reduce their visibility from Earth.

In a letter to the Federal Communications Commission (FCC), SpaceX said it was lowering the altitude of 300 satellites to lower Earth orbits as part of an effort to reduce Starlink’s impact on optical astronomy. This approach has been successful: the number of satellites illuminated by the Sun and visible in images from the Vera Rubin Observatory in Chile has decreased by almost 60%.
“Clogging” of Earth orbit
Low Earth orbit is becoming increasingly crowded with satellites, most of them owned by SpaceX. There are now 6,912 Starlink satellites in orbit about 550 kilometers above Earth. The reflection of sunlight by these satellites creates unwanted streaks in astronomical images. The first Starlink models were so bright that they could be seen with the naked eye, and their impact on telescopes was significant.

In December 2022, the FCC authorized SpaceX to launch up to 7,500 next-generation satellites, larger and brighter than previous ones. The weight of the new generation is about 1,250 kg, while the first models weighed only 260 kg. These satellites are expected to be a full star magnitude brighter.
Help for astronomers
SpaceX is working with the National Science Foundation (NSF) to reduce the impact of satellites on optical astronomy. One of the solutions was to reduce the altitude of the Starlink demonstration satellites to 350 km. This helps to reduce their ability to reflect sunlight. In a letter to the FCC, SpaceX explained that satellites in lower orbits spend more time in Earth’s shadow and move faster, which reduces their brightness to ground observers.
NSF confirms that this strategy can be useful. At lower altitudes, satellites pass through the telescopes’ field of view faster, reducing brightness per pixel. They are also in the Earth’s shadow for most of the night, which reduces their visibility to below the threshold visible to the naked eye.
Attempts to reduce the impact on observation
SpaceX has already taken steps to reduce Starlink’s impact on astronomy. Together with the International Astronomical Union, the company looked for ways to reduce the reflectivity of satellites. This included changing the orientation of satellites, solar panels and installation of special canopies to reduce their brightness.

Despite the positive results, the strategy of reducing satellite altitude has disadvantages. In smaller orbits, they can be brighter during twilight, which affects the research that takes place at that time, particularly the observation of near-Earth objects. NSF plans to continue working with SpaceX to evaluate the effectiveness of these measures.
The growing number of satellites in orbit is a common problem. If more companies do not take steps to reduce their influence on astronomy, it could significantly limit the ability to observe space.
According to PC Mag