by WASHINGTON – The first satellites from a Chinese broadband constellation are significantly brighter than those from Western systems, posing a new challenge for astronomers.
In a paper posted to the arXiv preprint server on September 30, a group of observational astronomers reported on observations from a series of 18 Qianfan or ‘Thousand Sails’ satellites launched in August. The satellites are the first of a constellation that could ultimately consist of more than 14,000 satellites.
The study found that the brightness of the satellites ranges from magnitude 8 when they are low in the sky, to magnitude 4 when they are almost overhead. That makes the satellites, at those higher altitudes, bright enough to be seen with the naked eye – which can see objects up to magnitude 6 in a dark sky – and well above the magnitude 7 threshold recommended by professional astronomers, it reduces the interference with major ground-based satellites. observatories.
“Qianfan satellites are brighter than magnitude 6 except when observed at low altitudes in the sky,” the astronomers note in the paper. “They will therefore negatively impact professional and amateur astronomical activities unless operators reduce their brightness.”
The study analyzed the change in brightness of the satellites as a function of altitude and found that it fit well with a model with a large flat antenna pointed toward Earth and a solar panel pointed away from Earth. That matched limited public information about the spacecraft’s design. The newspaper added that there was no evidence that the satellites contained measures such as mirrors to reflect light away from Earth, as SpaceX has built into Starlink satellites.
The astronomers involved in the study, some of whom are with the International Astronautical Union’s Center for the Protection of Dark and Quiet Skies from Satellite Constellation Interference (CPS), said they conducted the research to raise awareness and hoping to bring about changes in the design. of later Qianfan satellites.
“SpaceX made changes to the design of their Starlink satellites because early observations showed that their Generation 1 spacecraft would have an impact on astronomy. That is our motivation to report the first results for Qianfan,” they wrote. Subsequent Starlink satellites now approach the CPS recommendation at magnitude 7.
It is unclear whether and how Shanghai Spacecom Satellite Technology, the developer of the Qianfan satellites, will respond to the investigation. A CPS spokesperson did not respond Oct. 3 to questions about whether the center had any contact with Chinese industry or government officials about the brightness of the satellites.
During a session of an American Astronomical Society meeting in January, CPS representatives said their contacts with China have been limited, mainly during meetings of the United Nations Committee on the Peaceful Uses of Outer Space.
The Qianfan satellites represent just some of the latest challenges facing astronomers. AST Space Mobile announced On October 4, the company announced that it had deployed the large phased array antenna on the first of five BlueBird satellites launched on September 12 to provide direct-to-device services. The antenna, covering an area of about 65 square meters, is one of the largest commercial antennas in low Earth orbit, and its size has raised concerns among astronomers about its brightness.
Radio astronomers, meanwhile, have reported low-frequency interference from Starlink satellites. A study published in September based on data collected by the Low Frequency Array (LOFAR) radio telescope found that Starlink “v2 mini” satellites produced signals that were much stronger than astronomical sources.
The emissions, found in several bands between 56 and 161 megahertz, were not linked to the broadband payloads of those satellites, which operate at much higher frequencies, but are instead likely unintended emissions from spacecraft electronics.
“Humanity is clearly approaching a turning point where we must take action to preserve our heavens as a window to explore the universe from Earth. Satellite companies are not interested in producing this unintended radiation, so minimizing it should also be a priority in their sustainable space policies,” Federico Di Vruno, spectrum manager of the Square Kilometer Array Observatory and co-director of CPS, said in a statement. “Starlink is not the only major player within LEO, but they have an opportunity to set the standard here.”
