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SpaceX reaches agreement with astronomers to limit Starlink interference

This week, National Science Foundation announced it has reached an agreement with SpaceX to limit the effects of Starlink satellites on astronomy.

Astronomers have been raising concerns about the effects that Starlink satellites could have on scientific study for several years now, as part of a wider consideration of the cultural and environmental importance of dark and quiet skies. The International Astronomical Union has even set up a special center for addressing the issue of satellite megaconstellations like Starlink on both optical and radio astronomy.

Image showing the disruption of astronomical observations caused by a previous Starlink launch
Around 19 Starlink satellites were imaged shortly after launch in November 2019 by DECam on the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO) by astronomers Clara Martínez-Vázquez and Cliff Johnson. The gaps in the satellite tracks are due to the gaps between the DECam CCD chips. NSF’s National Optical-Infrared Astronomy Research Laboratory/CTIO/AURA/DELVE

There are two main concerns about the impact of Starlink on astronomy. Firstly, that satellites are reflective so they reflect light from the sun, leading to bright streaks in optical astronomical observations of the night sky. This is a particular problem for Starlink compared to other types of satellites as the Starlink satellites sit in very low Earth orbit, meaning they are more prominent in the sky, and there are thousands of them.

SpaceX has been working with astronomers to reduce this issue through methods like painting the satellites a darker color to make them less reflective, adding sunshades, and changing their orientation so they reflect less sunlight.

The second problem is with radio astronomy. Satellites are designed to operate at a particular radio frequency, however, they can give off radiation outside that band in a phenomenon called frequency bleed. Radio astronomers already have to deal with a lot of background radio noise from Earth to pick out the faint signals from the distant objects they are observing, and having many satellites in the sky makes that harder.

The agreement focuses on the 10.6 – 10.7 GHz radio astronomy band, and SpaceX has agreed to take steps such as not transmitting from the satellites when they are passing over major radio astronomy stations.

The agreement is not legally binding, but it does show that both groups are trying to work together to both enable global satellite internet and allow astronomical observations. “We are setting the stage for a successful partnership between commercial and public endeavors that allows important scientific research to flourish alongside satellite communication,” said NSF Director Sethuraman Panchanathan in a statement.

However, not all astronomy groups are so positive. As SpaceNews reports, the International Dark-Sky Association is currently involved in a court case attempting to block the deployment of more Starlink satellites on the basis that they are harmful to both professional and amateur astronomy.

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