16 hours ago
Oh Great, Starlink Might Be Blocking Signals That Are Basically From the Dawn of Time
Here's what you'll learn when you read this story:
SpaceX's Starlink satellites were known to interfere with visible light astronomical observations, but many have now been found to be interfering with radio observations by leaking radio emissions.
While this is unintentional, unchecked leakage of radio waves could block observations that go back to when the universe was only a billion years old.
Starlink needs to intervene as soon as possible, before the emissions end up blocking faint light from the Epoch of Reionization—when neutral hydrogen was reionized by light from the first stars.
Mega-constellations of satellites are connecting more and more of the world to the internet, beaming it down to Earth on an unprecedented scale. Unfortunately, in that process, they seem to be putting other scientific efforts at risk.
With over 7,600 small satellites hovering in low-Earth orbit (LEO) and a total of 12,000 (with an extension to a possible 36,000) planned, SpaceX's Starlink is without a doubt the largest satellite mega-constellation bringing internet to the masses. But it comes at a cost—while Starlink is in compliance with regulations intended to keep it from interfering with scientific observations, unintentional leakage of radio waves from thousands of its satellites has reached a level that could severely interfere with observations of faint radio sources going back to the early days of the universe. SpaceX has managed to prevent some interference by switching off beams that transmit internet when their satellites pass over telescopes, but that hasn't cancelled out the entire problem.
Astronomer Steven Tingay of Curtin University's International Center for Radio Astronomy Research in Australia is concerned. He and colleagues Dylan Grigg and Marcin Sokolowski investigated the types of emissions that were leaking from Starlink satellites, how much of these emissions were being released, and in what ways the mega-constellation could have a negative impact on Earth-based radio observations. He previously used the SKA-Low prototype station to analyze satellite constellation impacts on radio astronomy.
'A small fraction of the radio spectrum across the SKA-Low's bandwidth has protection for radio astronomy,' Tingay, Grigg, and Sokolowski said in a study recently posted to the preprint server arXiv. 'Although these protections exist, a succession of research has shown that an increasing number of satellites are being detected transmitting unintended electromagnetic radiation (UEMR) outside their designated downlink frequencies, and sometimes at these protected frequencies.'
Some of SKA-Low's bandwidth—3.7 percent, to be exact—is protected by the International Telecommunications Union's Radiocommunication. But 3.7 percent is proving not to be enough. Starlink launches were already problematic when Tingay and his team conducted the study, with 477 satellites being sent to space during the four months they were collecting data. The two frequencies being released by many of the satellites in the constellation were 137.5 MHz and 159.4 MHz, which are two of the same radio frequencies at which astronomical observations are made.
Tingay's team conducted the largest survey of Starlink satellites at SKA-Low frequencies. While there are there different models of satellite producing varying emissions, most of the ones that were leaking the problematic radio waves were type v2-mini-Ku (though, some v2-mini DTC and v1.5 models were also emitting waves at these frequencies). Starlink owns 75% of the v2-mini-Ku satellites in orbit, meaning that the company has the greatest responsibility when it comes to leakage from from these particular models.
Leakage may go beyond interference in certain domains, even going so far as to potentially block observations that go all the way back to the Epoch of Reionizaiton—about a billion years after the Big Bang. This was when most of the electrically neutral hydrogen in the universe was charged by rising levels of radiation from the most ancient massive stars, known as Population III or Pop III stars (no Pop III stars have been detected yet). If left unchecked, radio emissions from Starlink satellites could get in the way of monumental discoveries.
'Future mitigation of the UEMR from Starlink satellites will be key for ultra-sensitive experiments with the SKA,' the researchers said. 'SpaceX has made significant progress liaising with astronomers in the optical domain, and we hope to keep this dialogue open in the radio domain.'
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