A new report issued by the United Nations Office for Outer Space Affairs dives into issues impacting affecting astronomical observation and what can be done to preserve it.

As one of those issues, the report looks at current estimates of satellites accessible to the unaided, naked eye, under dark night skies. All sunlit satellites in large constellations “are detectable by any research telescope, sometimes even inducing saturation effects that may ruin not only the image area affected by the trail, but a much larger region, potentially the whole image in some cases,” the report explains.

Starlink satellites visible in a mosaic of an astronomical image.
Courtesy of NSF’s
National Optical-Infrared Astronomy Research Laboratory/NSF/AURA/CTIO/DELVE)

Visibility of the night sky

“The deployment of large numbers (tens of thousands) of communication satellites in LEO (Low Earth Orbit) is a very recent technological feat,” the report adds. “Their main purpose is to provide earth-space-earth, low latency communication networking to any inhabited region of the globe. While this endeavor may be an advantage to society, the effect of the fully deployed constellations on the visibility of the night sky and on the professional astronomical observations has not been adequately considered.”

The report — Dark & Quiet Skies for Science & Society: Report and Recommendations – calls for raising awareness of the impacts of satellite constellations and possible mitigation strategies and their costs and requirements amongst key astronomy stakeholders.

An image of the NGC 5353/4 galaxy group made with a telescope at Lowell Observatory in Arizona, USA on the night of Saturday 25 May 2019. The diagonal lines running across the image are trails of reflected light left by more than 25 of the 60 recently launched Starlink satellites as they passed through the telescope’s field of view. Although this image serves as an illustration of the impact of reflections from satellite constellations, please note that the density of these satellites is significantly higher in the days after launch (as seen here) and also that the satellites will diminish in brightness as they reach their final orbital altitude.
Credit: Victoria Girgis/Lowell Observatory

Satellite-induced artifacts

In the report’s “Recommendations for Observatories,” there’s need to support the development of software applications to conduct long term planning and simulations of observations, scheduling, and to identify and remove satellite-induced artifacts from data. This requires a range of data from industry on satellite reflectance, antenna parameters, and predicted and real-time ephemerides.

Furthermore, the report notes, observatories will also require additional funding for development and to assess overall impacts on science programs. Also, plan for more stringent requirements on future designs of observing facilities “to account for the additional losses from satellite constellations, including additional telescopes, increased apertures, additional tools for image processing, higher robustness receivers, and enhanced detector technologies. These measures require additional funding.”

Starlink satellites.
Credit: SpaceX

Recommendations to be reviewed

Upon request from the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS), the UN Office of Outer Space Affairs, the International Astronomical Union and Spain are organized an online workshop, held October 5-9, 2020. The just-issued report is the outcome from this workshop.

The recommendations it contains will be reviewed during a forthcoming conference with the aim to be presented to the COPUOS Meeting in June 2021.

To read the full report, go to:


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