A Sky Full of Satellites

The number of active satellites in Earth orbit has increased fivefold in the past decade and is expected to increase by at least one further order of magnitude in the next decade. The advent of large constellations of big satellites in low orbit will transform the night sky and present a challenge to wide-field ground-based astronomical imaging.

I discuss the rapidly changing demographics of the current low Earth orbit artificial satellite population and show that the proposed "megaconstellation" of circa 30,000 Starlink internet satellites dominates the lower part of Earth orbit, below 600 km. Such large, low altitude satellites appear visually bright to ground observers, and Starlinks are naked eye objects. Higher orbit satellites such as the OneWeb constellation are fainter but have a larger impact on optical ground-based imaging. I model the expected number of illuminated satellites as a function of latitude, time of year, and time of night and summarize the range of possible consequences for ground-based astronomy. In winter at lower latitudes typical of major observatories, the satellites will not be illuminated for six hours in the middle of the night. However, at low elevations near twilight at intermediate latitudes (45-55 deg, e.g. much of Europe) hundreds of naked-eye satellites may be visible at once to observers and wide field deep images may have of order 1 satellite trail per exposure, or more, throughout the summer night. Astronomers are engaging with regulators both in the US and internationally to argue that the night sky should be considered an environmentally protected resource and large constellations should be regulated with this in mind.

Видео A Sky Full of Satellites канала CfA Colloquium