The National Science Foundation & SpaceX sign agreement to ensure Starlink satellites do not interfere with ground-based astronomy

Astronomers have voiced their concerns over SpaceX’s Starlink constellation potential to interfere with ground-based observations. The National Science Foundation (NSF) and SpaceX signed an agreement to ensure the Starlink satellites do not affect ground-based astronomy. “We are setting the stage for a successful partnership between commercial and public endeavors that allows important science research to flourish alongside satellite communication,” said NSF Director Sethuraman Panchanathan.

SpaceX worked with NSF and its radio astronomy observatories to mitigate potential interference from SpaceX Starlink satellite transmissions, focusing on the 10.6 – 10.7 GHz radio astronomy band and signed a coordination agreement in 2019 to ensure the Starlink meets international radio astronomy protection standards for that specific band used by astronomers. This collaboration continues. On January 10, NSF shared it signed a new coordination agreement with SpaceX in late-2022 after the Federal Communications Commission (FCC) approved SpaceX to launch 7,500 Generation 2 (Gen2) Starlink satellites in December. These next-generation satellites are designed to increase the broadband network’s capabilities and expand internet access globally. “NSF and SpaceX agreed to cooperate to the extent practicable to mitigate the impact on optical and infrared ground-based astronomical facilities. SpaceX committed to continue work towards recommendations that came from NSF’s NOIRLab, the American Astronomical Society’s SATCON workshops and the International Astronomical Union’s Dark and Quiet Skies best practices guidance,” said NSF representatives in an announcement. “These recommendations include continuing to work to reduce the optical brightness of their satellites to 7th visual magnitude or fainter by physical design changes, attitude maneuvering, or other ideas to be developed; maintaining orbital elevations at ~700 km [kilometers] or lower; and providing orbital information publicly that astronomers can use for scheduling observations around satellite locations,” stated NSF.

SpaceX engineers also worked with observatory telescope operators to analyze the potential impact of astronomical observatory lasers on its Starlink satellites. Following an analysis, the Laser Clearinghouse removed coordination requirements for use of lasers because it has no interference with the satellites. Previously, astronomers and SpaceX had to coordinate when to use lasers at ground-based telescopes because of the Starlink satellites passing above the observatories but now they determined that it is not necessary. SpaceX and NSF’s National Radio Astronomy Observatory (NRAO) initiated a pilot program to test the impact of SpaceX Starlink user terminals in close proximity to radio astronomy facilities, such as the Very Large Array (VLA).  

SpaceX engineers have also been working with leading astronomers to minimize the potential of Starlink satellites looking ‘too bright’ from Earth. The first-generation Starlink satellites are equipped with ‘sun visors’ that block sunlight from hitting the bottom of the satellite chassis. “SpaceX successfully developed material for the visors that was transparent to radio frequencies and would not block the user-serving antennas of SpaceX's satellites. Unfortunately, the material did block the laser links that SpaceX needs to expand coverage to the most remote regions of the world. The visors also generated significant drag on the satellites,” said SpaceX. “Because SpaceX operates at such low altitudes, this higher drag requires more thruster fuel expenditure to increase orbit altitude and station-keep once at the operational altitude. For these reasons, SpaceX ultimately determined that its sun visors were not a viable long-term solution. As an alternative to sun visors, SpaceX started developing RF-transparent mirror films. This dielectric mirror film specularly scatters the vast majority of sunlight away from the Earth. SpaceX has been continually improving its mirror films to scatter less light back to Earth, and will be deploying a new and improved version of this film on our next-generation satellites,” the company shared. 

As part of the newest NSF agreement, SpaceX engineers designed the Gen2 Starlink satellites with upgraded mitigation measures which include: dielectric mirror film, solar array mitigations, and new black paint that minimizes brightness and glints. The company says the second-generation Starlink satellites will look significantly darker in orbit compared to the first-generation. The company is also painting all components on Gen2 Starlink satellites with ‘black paint’, components such as screws and brackets, and other onboard components that may glint with the sun. “To mitigate these potential glints, SpaceX internally developed a ‘Low Reflectivity Black’ paint, which has a five-times lower specular peak compared to the darkest available space stable paint,” the company said. “SpaceX’s goal is to make its second-generation satellites invisible to the naked eye when they are on station serving users, covering the vast majority of each satellite’s lifetime. However, there are a few phases of flight where satellites are expected to be visible for small portions of their life,” the company said. The moments of potential visibility include: immediately after a Starlink satellite is launched to Low Earth Orbit, as the satellite is raising into its operational orbit, and when satellites perform thruster burns for collision avoidance or station keeping. The satellites will also appear brighter when they deorbit and burn up upon reentering Earth’s atmosphere at the end of their useful life. 

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Featured Image Source: Gemini Observatory