Enlarge /. Artist's impression of the low-earth orbit satellites launched by SpaceX and OneWeb.
Broadband satellites launched by SpaceX and other companies will inevitably have a negative impact on astronomers' ability to observe the night sky, according to a new report from astronomers. There are no mitigation strategies that can completely eliminate the satellites' impact on astronomical observations – other than not launching satellites at all – but the report does make recommendations on how satellite operators can minimize disruptions and how observatories can adapt to the changes.
The report, published this week, is entitled "Effects of Satellite Constellations on Optical Astronomy and Recommendations for Mitigation". The report is the result of the recent Satellite Constellations 1 (SATCON1) workshop jointly organized by the National Science Foundation's NOIRLab and the American Astronomical Society (AAS). The SpaceX engineers attended the online workshop, but the report was written by members of the SATCON1 Scientific Organizing Committee and represents their consensus views. Committee members come from NOIRLab, AAS, the Lowell and Steward Observatories in Arizona, the Rubin Observatory in Chile, the University of Michigan, UC-Davis, Smith College, and the Association of Universities of Astronomical Research (AURA) .
The report said:
Changes are needed at both ends: constellation operators and observatories. SpaceX has shown that operators can reduce reflected sunlight through satellite body alignment, sun protection, and surface darkening. A concerted effort to get more accurate public data on predicted locations of individual satellites (or ephemeris) could allow for some avoidance of pointers and shutter speed at medium exposure during satellite passageway. Observatories must adopt more dynamic planning and observation management as the number of constellation satellites increases, although even these measures will be ineffective for many scientific programs.
SpaceX has launched over 600 satellites to date and OneWeb has launched 74. Both companies plan to put tens of thousands of satellites into low-earth orbits and provide broadband to areas that lack fast wired service. Amazon also plans to launch thousands of satellites. Because of their near-earth orbits (LEO), the satellites offer lower latency than conventional satellite networks.
Musk did not predict any effects
SpaceX CEO Elon Musk said in March that he was "confident that we will have no impact on astronomical discoveries." He said the satellites were visible immediately after launch because "they tumble a little" and essentially "blink" or "reflect in a way that is not the case in orbit". Once satellites stabilize and begin to raise their orbits, they shouldn't cause problems for astronomers, Musk said.
But it's been over a year since SpaceX began launching broadband satellites, and astronomers have now "collected enough observations from constellation satellites such as those launched by SpaceX and OneWeb, and performed computer simulations of their likely effects to size." and complexity of the satellites to understand problem, "says the SATCON1 report.
Enlarge /. A wide-field image (2.2 degrees in diameter) from the Dark Energy Camera on the 4-meter Víctor M. Blanco telescope at the Cerro Tololo Inter-American Observatory, taken on November 18, 2019. Several Starlink satellites crossed the field of view.
"If the 100,000 or more LEOsats proposed by many corporations and many governments are deployed, no combination of attenuations can completely avoid the impact of satellite paths on current and proposed ground-based NIR optical astronomy (near infrared) astronomy facilities," it said in the report. "Astronomers are just beginning to understand the full implications for the discipline. Astrophotography, amateur astronomy, and the human experience of the stars and the Milky Way are already affected."
The report's authors said they "ran simulations of representative LEOsat constellations" to reach their conclusions. Recommendations for minimizing damage to astronomy "are based on the work and collaboration between astronomers and SpaceX," but are "intended for a wide audience and, in particular, the entire satellite constellation industry," the report said.