Astronomers fear that without remedial action, large satellite installations will impact our ability to observe stars from Earth, even with radio astronomy
Several companies are planning satellite constellations, groups of hundreds of satellites that can provide cellular or broadband services anywhere in the world. However, these satellites must be in low Earth orbit and can be relatively large, so their potential to disrupt night sky observations is a concern.
Now an international team of scientists led by astronomers from IAU’s Center for the Protection of Dark and Quiet Skies from Satellite Constellation Interference (CPS), including researchers from Imperial College London, have published an article in Nature detailing the implications The BlueWalker evaluates 3 satellite prototypes for astronomy.
Dr. Dave Clements, from the Imperial Department of Physics, said: “The night sky is a unique laboratory, allowing scientists to carry out experiments that cannot be carried out in terrestrial laboratories.” Astronomical observations have insights into fundamental physics and other research at the frontiers of our knowledge delivered and changed humanity’s view of our place in the cosmos. “The pristine night sky is also an important part of humanity’s shared cultural heritage and must be protected for society as a whole and for future generations.”
BlueWalker 3 was launched into low Earth orbit by AST SpaceMobile on September 10, 2022, as a prototype of a planned constellation of more than a hundred similar satellites for mobile communications. Observations made a few weeks after launch showed that the satellite was among the brightest objects in the sky.
However, to better understand its impact on astronomy, the CPS launched an international observation campaign. This initiative contributed both professional and amateur observations from around the world, from locations in Chile, the USA, Mexico, Aotearoa, New Zealand, the Netherlands and Morocco.
The newly released data documents BlueWalker 3’s luminosity over a period of 130 days and shows a steep increase that coincides with the full deployment of the antenna array, which at 64 square meters is the largest commercial antenna system ever deployed in Earth orbit. low .
Some of the observations were also used to calculate the satellite’s trajectory over time. By comparing the predicted trajectory with the collected observations, the authors were able to assess the accuracy of the predictions and see how this can change due to factors such as air resistance.
Knowing the location of satellites is important so that astronomers can try to avoid them or at least know where they appear in the data. However, it is difficult to reduce the brightness other than obscuring your position and losing data for that part of the sky.
In addition to visible observations, BlueWalker 3 could also disrupt radio astronomy because it uses wavelengths similar to those at which radio telescopes observe. Although some telescopes are located within designated radio silence zones, the restrictions protecting these zones currently only apply to ground-based transmitters, so they are not necessarily protected from satellite transmissions.
Dr. Mike Peel, co-director of the IAU CPS Sathub project and researcher at the Imperial Department of Physics, said: “BlueWalker 3 is actively transmitting on radio frequencies close to the bands reserved for radio astronomy, and existing observatory protections against radio interference may not be possible .” are sufficient. “Therefore, further research is needed to develop strategies to protect current and future telescopes from the numerous satellites planned for launch in the next decade.”
The IAU and CPS partners recognize that new satellite constellations play an important role in improving global communications. However, its interference with astronomical observations could seriously hinder advances in our understanding of the cosmos. Therefore, their use must be carried out with due consideration of their side effects and efforts to minimize their impact on astronomy.
BlueWalker 3’s observations continue and astronomers plan to observe its thermal emission later this year.
The high optical brightness of the BlueWalker 3 satellite