A new study commissioned by the European Southern Observatory suggests that the introduction of 26,000 new constellations of giant satellites could have a significant impact on ground astronomy. The number of satellites visible to the naked eye will triple over the next few years as companies such as SpaceX, OneWeb and Amazon pursue their ambitious orbit plans.
Advances in human technology seem to inevitably be inextricably linked to the increasing pollution of the natural environment. On Earth, industrialization has changed the global climate, with potentially far-reaching and huge consequences, and the advent of modern consumerism has polluted the oceans with plastic waste. With people’s grasp of orbit domain more and more, the space environment also began to be damaged by human pollution. For example, the current proposed giant satellite constellation could see nearly 26,000 satellites launched into low-Earth orbit over the next few years, compared with about 5,000 satellites that remain in orbit.
The Giant Satellite Constellation is a collection of large numbers of satellites flying in formation in low-Earth orbit. SpaceX is already building its Starlink project, which Elon Musk hopes will one day provide low-cost Internet access worldwide. The company is busy launching the satellites from the Falcon 9 rocket. SpaceX isn’t the only company looking to use satellite groups to provide Internet services. OneWeb also wants to create an orbital network of hundreds of satellites, as does global giant Amazon.
The proliferation of satellite technology and the emergence of giant satellite constellations have not only produced physical contamination in the form of failed satellites, but, in the worst case, debris from orbital collisions. It also has the potential to seriously interfere with astronomical observations. These hordes of detectors will relentlessly pass through the sight of powerful telescopes that capture detailed observations of cosmic objects, reducing the mass of the data set.
The scientists behind the new study have modelled the impact of giant satellite constellations on ESO telescopes that make visible and infrared observations, such as the Very Large Telescope in Chile’s Atacama Desert. The paper considers a number of factors, as well as different ways for telescopes to observe the sky.
The results showed that observations that relied on short-term exposure were affected by satellite flares only 0.5 per cent of the time, most of the time at dusk. Astronomers are actively observing the night sky after dusk or before dawn, but there is enough sunlight around the Earth’s curvetoe to illuminate the massive metal detectors that pass overhead. At dusk, telescopes that require a longer exposure time (about 1,000 seconds) will be affected by about 3% of the time.
The wide area used to constantly gaze at the night sky in search of fleeting events such as new stars, long-exposure observations will be most affected by satellite constellations. For example, the Vera Rubin Observatory of the National Science Foundation will be affected by satellites 30 to 50 percent of the time of year, depending on the time of year.
The study also mentions two main ways astronomers can try to mitigate the damage caused by satellite constellations to their observations. The first method is to arrange for its telescope to capture the sky when there is no satellite in a given area. Satellite paths are predictable, so this is a viable technology. However, it does not apply to every type of observation. For example, satellite contamination may not be avoided when long periods of wide field of view exposure are required. The second approach involves interrupting the telescope’s guard by precisely determining when a bright satellite is passing through the field of view and closing the shutter before the contact time. This will be a challenging technique and will not work at all for wide field observations.
On the industrial side, manufacturers can darken the surface color of satellites, reducing reflections. SpaceX has experimented with this approach in one of its Starlink satellites, although it must be widely disseminated to be effective. The study also touched on the impact of the giant satellite constellation on the public night sky. At the mid-latitudes, 1,600 satellites will appear above the horizon, the researchers said. This could lead to a threefold increase in the number of satellites visible to the naked eye in the night sky.
The study aims to provide a simple assessment of the impact of satellite constellations on scientific observations, rather than a comprehensive study of potential damage. To arrive at conservative estimates, researchers must make some well-founded guesses about important elements, such as the distribution and brightness of satellites. The study authors note that their results “may be wrong on the pessimistic side” and that further research using more complex models will help reveal the nature of future interference and explore its impact on radio, millimeter and submillimeter wave wavelength observations.
The paper has been published in the journal Astronomy and Astrophysics.