Observations of the BlueWalker 3 prototype satellite show that it is one of the brightest objects in the night sky, outshining all but the brightest stars. Astronomers have expressed concern that without action, large constellations of satellites could deprive us of the ability to observe stars from Earth and participate in radio astronomy.

Many companies plan to create satellite constellations consisting of hundreds of satellites that can provide mobile or broadband services anywhere in the world. But these satellites must be in “low Earth” orbit and can be relatively large, so their potential to interfere with observations of the night sky is a concern.

Now an international team of scientists, led by astronomers from the IAS Center for Protecting Dark and Quiet Skies from Satellite Interference (CPS), including researchers from Imperial College London, has published a paper in the journal Nature assessing the impact of satellite interference. Prototype in detail. BlueWalker 3 Astronomy Satellite.

Dr. from Imperial University’s Department of Physics. Dave Clements said: “The night sky is a unique laboratory that allows scientists to perform experiments that cannot be performed in terrestrial laboratories. Astronomical observations have allowed us to delve deeper into fundamental physics and other research within the limits of our knowledge, and have changed humanity’s view of our place in the universe. “The original night sky is also an important part of humanity’s shared cultural heritage and must be preserved for society as a whole and for future generations.”

brilliant observations

BlueWalker 3 was launched into low Earth orbit by AST SpaceMobile on September 10, 2022, as the prototype for a planned constellation of more than a hundred similar satellites designed for use in mobile communications. Observations made in the weeks after launch showed that the satellite was one of the brightest objects in the sky.

But to better understand its impact on astronomy, CPS has launched an international observing campaign. As part of this initiative, both professional and amateur observations were provided from around the world from facilities in Chile, the USA, Mexico, Aotearoa, New Zealand, the Netherlands and Morocco.

New data documenting BlueWalker 3’s brightness over 130 days shows a dramatic increase coinciding with the full deployment of the antenna array, the largest commercial antenna system ever deployed into low Earth orbit at 64 square metres.

Some of the observations were also used to calculate the satellite’s orbit over time. By comparing the predicted path with collected observations, the authors were able to evaluate the accuracy of the predictions and how these predictions might change due to factors such as atmospheric drag.

Knowing the positions of satellites is important so that astronomers can try to avoid them or at least know where they will be in the data. However, it is difficult to soften the brightness other than masking their location and losing data on that part of the palate.

Radio Initiative

In addition to visible observations, BlueWalker 3 may interfere with radio astronomy because it uses wavelengths close to those observed by radio telescopes. Although some telescopes are located within certain radio-quiet zones, current restrictions to protect these areas currently apply only to ground-based transmitter observations, so they are not necessarily shielded from satellite transmission.

Sathub IAU CPS President and researcher at Imperial’s Department of Physics, Dr. “BlueWalker 3 is actively transmitting at radio frequencies close to the bands reserved for radio astronomy, and observatories’ current protection against radio interference is sufficient,” said Mike Peel, “so we are working to develop strategies to protect current and future telescopes from the many satellites planned to be launched in the next decade.” More research is needed.”

The IAU and CPS partners recognize that new satellite constellations play an important role in improving global communications. But their interference with astronomical observations could seriously hinder our progress in understanding the universe. Therefore, their distribution should be done taking into account their side effects and efforts to minimize their impact on astronomy.

Observations of BlueWalker 3 will continue, and astronomers plan to observe its thermal emission later this year. Astronomers will continue to discuss this issue at the IAS Astronomy and Satellite Clusters: Pathways Forward Symposium in October.