(Credit: PCMag/Michael Kan)
Amazon Leo is following in Starlink’s footsteps, but in a way astronomers hoped it would avoid. Many of the Leo satellites appear to be bright enough in the night sky to interfere with astronomical observations, according to new research.
The findings come from a group of astronomers affiliated with the International Astronomical Union that took nearly 2,000 observations of Amazon’s commercial Leo satellites, which the company started launching into Earth’s orbit last year.
Satellites can reflect sunlight to observers on the ground in the hours after dusk and before sunrise. The research found that when Leo satellites have entered operational altitude at around 630 kilometers, 92% of the observations showed the satellites exceeding the recommended brightness guidelines from the astronomical community.
(Credit: Brightness Characterization and Modeling for Amazon Leo Satellites)That said, the Leo satellites are still fairly dim in most cases. Only about 25% of the observations found the satellites were vivid enough to be visible to the human eye—or under a 6 on the stellar magnitude scale that astronomers use to classify brightness.
Magnitude 6 represents the “aesthetic limit" for when a satellite or star becomes visible to the unaided eye. However, the International Astronomical Union has been urging satellites to reduce their brightness even lower, beyond magnitude 7, to avoid interfering with telescopes, which can still spot even fainter objects in the night sky.
(Credit: Earthsky.org)It's why the research still flags the Leo constellation as a concern. “The mean apparent magnitude of all Amazon Leo satellites is 6.28 based on 1,938 observations,” the paper added.
In addition, the research notes the Leo satellites feature “reflective characteristics” similar to first-generation Starlink satellites, which have also faced complaints about interfering and photo-bombing astronomical observations. In response, SpaceX has made various efforts to reduce their brightness by incorporating a “mirror film” and even painting them black.
Like SpaceX, Amazon also told PCMag it’s already working with astronomers to address the brightness concerns. This has included using its own anti-reflective coating on the Leo satellites.
“Space safety and sustainability have always been key considerations for the Amazon Leo team, and we’ve made several design and operational decisions to help reduce our impact on astronomical research, from our close coordination with astronomers to applying a custom dielectric film and non-reflective coating on all of our operational spacecraft,” a company spokesperson said.
Amazon has already launched 180 Leo satellites with plans to send up over 3,200 for the first-generation constellation. So, astronomers are hoping the company can make changes as more satellites launch. The research paper even thanks Chris Hofer, Head of International Spectrum Management and Strategy at Amazon Leo, for his input.
(Credit: Brightness Characterization and Modeling for Amazon Leo Satellites)Still, research last year found that most satellites from the newest constellations are failing to meet the brightness recommendations from the astronomical community, raising concerns it may be impossible for satellite operators to hit the guideline.
In the meantime, Amazon noted: “We’re encouraged by the initial results of that work and expect to continue improving as more satellites reach assigned altitudes. We’ll continue to invest in this research and development, and look forward to continuing our work with the scientific community to learn and iterate further.”
Last year, the company also signed an agreement with the US National Science Foundation to minimize Leo’s potential interference on astronomy research.