If the light pollution of satellite megaconstellations on optical telescopes is now known and documented, the impact of telecommunications in lower orbit on radioastronomy is a little more recent concern. But quantifying the phenomenon is not simple. This is what a team of scientists from Curtin University, Australia, whose work was published on July 17, did in the review Astronomy & Astrophysics. The researchers analyzed more than 76 million images, taken for a total period of twenty-nine days, using the Engineering Development Array 2 (EDA2), a prototype radiotelescope established in the Australian West desert. On the same site, he precedes part of the future Square kilometer array (SKA), the largest and more powerful radio station in the world, which must enter into activity by 2028.
Result ? Astronomers have detected, over these twenty-nine days, no less than 112,534 radio signals from 1,806 Satellites Starlink, the Satellite Internet provider of the SpaceX company, identified one by one by researchers. “On certain data, we have observed that up to 30 % of images presented radio interference from Starlink satellites”specifies Dylan Grigg, principal author of the study and doctoral student at Curtin University. Even more annoying, part of these satellites emit on frequencies protected by the International Telecommunications Union (ITU) – for example, 703 of them were identified as issuing on frequencies between 150.05 and 153 megahertz, a beach which, as 3.7 % of the spectrum of the radio domain, is protected, and on which no emission is not authorized, so as not to hinder signals from the deep sky.
Insufficient “shields”
These programs are nevertheless incident: they are not wanted, but rather result from mechanisms that Starlink engineers had not necessarily anticipated. According to the authors of the study, Elon Musk’s company had initially suggested that they could come from the satellite propulsion system, because they had been observed when the orbit of these was enhanced to reach their operational altitude. But these emissions are also detected on satellites who have reached their final orbit. The authors now hypothesize that the signals would come from the satellite on -board electronics, which would be insufficiently “armored”. “As these emissions are not part of an intentional signal, astronomers cannot easily predict them or filter them”explains Mr. Grigg.
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