New frontiers-both in space and challenges to the space above- are being opened by the growing deployment of satellite constellations driven by SpaceX’s Starlink. According to a study published Monday in Astronomy and Astrophysics, satellites are interfering with cosmic observations. With observations using the Low-Frequency Array telescope in the Netherlands, researchers were able to detect unwanted electromagnetic emissions from 68 Starlink satellites, raising concerns for radio astronomy.
Federico Di Vruno, a spectrum manager at the Square Kilometre Array Observatory, puts it more ominously thus: The huge number of foreseen satellites may cause a very serious impact on radio astronomy. Given that SpaceX intends to launch 42,000 of them, and over 4,000 are already up there, the potential for interference is gigantic. On July 15th, another 54 joined them in SpaceX’s Falcon 9.
For observing the celestial phenomena, the electromagnetic spectrum is a must, and frequencies within the range of 30 MHz to 300 GHz are mainly used. Di Vruno says that the radiation coming from individual satellites is somewhat comparable to the amount of radiation emitted by television; the problem lies in the cumulative quantity of thousands of satellites. The frequency range of 110-188 MHz from 47 Starlink satellites was found to emanate radiation within a band protected by the International Telecommunications Union. However, current regulations do not protect terrestrial radio telescopes against such interference.
The problem is not confined to Starlink. Other constellations, like OneWeb, are adding their own to the burgeoning population of satellites in low Earth orbit. Radio astronomers have tolerated excessive “noise” created by satellites for many years, but the sheer scale of these new constellations brings problems they have never faced. An agreement between SpaceX and the National Science Foundation tries to restrict interference in some frequency bands, but there are persistent anxieties over the increasing volume of information that is not useable.
Yvette Cendes, a radio astronomer at the Harvard-Smithsonian Center for Astrophysics, described the interference as being similar to going into a room where the lights are off and suddenly somebody turns on a powerful light: “And you are immediately blinded, and so you can’t see anything else except that light.” The authors of the study are talking to SpaceX about ways it might reduce this kind of accidental radiation.
I ask this question in my recent book, “Losing the Sky,” says Andy Lawrence, an astronomer at the University of Edinburgh who has investigated the wider ramifications of mega-constellations. Of course, I am happy to have all of humanity provided with broadband-no problem, he continues. But at what cost to the sky? The answer, he says, lies perhaps in international regulation, but even that will take some time.
Equally, the debate surrounding satellite constellations is not a purely scientific one; it addresses strategic matters, for these networks will play a crucial role in global communications and surveillance. In this respect, with increasingly crowded skies, military implications cannot be ignored.