Mega-satellite Constellations in Development Could Harm Astronomical Observations, Scientists Find

Several companies are in the process of developing satellite mega-constellations for communications purposes, which will involve launching thousands of additional spacecraft into relatively low orbit around the Earth.

Now, researchers have found that these projects could have a negative impact on astronomical observations, supporting the views of many experts in the astronomy community who are concerned about the impact on scientific research.

The European Space Agency estimates that there around 5,500 artificial satellites in orbit, of which about 2,300 are still functional. But SpaceX alone, for example, plans to launch an additional 12,000 into orbit—a process which has already started—as part of its Starlink mega-constellation initiative, which aims to provide low-cost internet to remote locations.

To understand the impact of projects like these on astronomical observations, Olivier Hainaut and Andrew Williams from the European Southern Observatory (ESO) examined the potential impact of 18 satellite constellations that are under development by SpaceX and others.

For the study—which has been accepted for publication in the journal Astronomy & Astrophysics—the researchers assumed that there will be a total of 26,000 constellation satellites in orbit around the Earth. However, they stress that this number is only representative and is subject to change.

Hainaut and Williams found that the planned constellations would have a severe impact on wide-field surveys conducted with large telescopes—depending on the time of year and night—such as the upcoming Vera C. Rubin Observatory which is currently under construction Chile. They estimate that between 30 and 50 percent of exposures with telescopes like these could be "severely affected."

These wide-field surveys are key for observing relatively short-lived astronomical phenomena, such as explosive supernovae or potentially hazardous asteroids.

They also found that the ESO's Very Large Telescope (VLT) in Chile and upcoming Extremely Large Telescope (ELT) could be "moderately affected" by the planned satellite constellations, particularly when it comes to long exposures—around three percent of which could be affected during twilight hours.

"Satellites used to be a minor nuisance. They were few, so a satellite crossing our field of view was rare. As their number increases, satellites will become a component of light pollution, just like street lights," Hainaut told Newsweek.

"We have been able to escape light pollution by setting our telescopes in the middle of the desert. We won't be able to escape satellites. Fortunately, it is possible to address the problem."

The first measure, according to Hainaut, is to dim the source of the light pollution. For street lighting, use better shades that point the light down rather than up, and use light wisely where it is needed.

The second is to build the "bottom" side of the satellite as dark as possible, so that it reflects less light, and design the satellite with as small a cross-section as possible.

"There are also ways to mitigate the existing satellites, but best is to make sure that those that are launched will not cause problems," Hainaut said.

The scientists note that their paper is only a starting point and more research needs to be carried out on this issue.

"There are many simplifications in this study. Each of these simplifications was done in a conservative—i.e. pessimistic—way," Hainaut said.

"The main limitation is that the study does not consider the latitude dependency of the satellites—my study is valid for low to mid-latitudes on Earth. At high latitude, there will be more satellites visible. At very high latitudes, there will be only very very few satellites.

"The goal was to get a first quantitative assessment of the situation. Others are working on more detailed studies, but as they are much more complicated, they take more time."

Newsweek has contacted SpaceX for comment regarding the potential impact of Starlink on astronomical observations.

Extremely Large Telescope
This image shows the night sky above the construction site of ESO’s Extremely Large Telescope. ESO/M. Zamani