Quirks & Quarks·Bob McDonald's blog

Astronomers anxious about plans to launch thousands of new satellites

New constellations of communications satellites could obscure the stars

New constellations of communications satellites could obscure the stars

Multiple Starlink satellites on their launch vehicle, after arrival in space, but before they were deployed. (SpaceX)

Astronomers are becoming more concerned with the increasing number of small satellites being launched into low Earth orbit that are blocking their view of the universe. 

Earlier this month, SpaceX launched 60 small satellites with a single Falcon 9 Rocket. This was the latest in a series of launches that are part of the Starlink Project, which is planned to eventually become a constellation of up to 12,000 satellites (yes, you read that right) providing worldwide broadband communication to help feed our appetite for internet connectivity.

This is just one of several such projects such as One Web which plans to launch a 900 satellite network and and Amazon's Kuiper project which plans a constellation of more than 3,200 orbiters. 

Together these projects threaten to cover the night sky with thousands more shiny objects that can interfere with telescope operations.

The impact of satellites on ground-based astronomy 

Last summer, the International Astronomical Union issued a statement on the impact of these satellites on ground-based astronomy. 

For optical astronomy, these satellites can interfere with telescope images, as sunlight glints off their shiny surfaces, producing streaks across long exposure photographs of the stars. The streaks can outshine stars themselves and render the scientific data useless, which is frustrating for astronomers trying to maximize precious telescope time. In addition, the satellites use radio frequencies to communicate with the ground, which can interfere with radio astronomers. There are even concerns about the effect so many satellites may have on nocturnal wildlife.

U.S. radio astronomy facilities are working with the communications industry to preserve clear views of the radio universe. (NRAO/AUI/NSF; J. Hellerman)

Currently, there are no international rules to control these mega-constellations. National regulators may require some conditions. The US FCC, for example, requires risk analysis of the threat of collision with other devices in orbit and also asks companies for plans to eventually de-orbit obsolete satellites. SpaceX's Starlink satellites are designed to de-orbit themselves, and have the ability to maneuver and avoid collision. But the sheer numbers of new satellites can't help but contribute to the growing problem of space debris

To study the depths of the universe, astronomers need dark skies, which are hard enough to find, considering all the light pollution that comes from cities and the natural barriers of clouds, dust in the air and shimmering air currents. Thousands of satellites passing overhead will add yet another obstruction to their window on the night sky.

A sky full of satellites taints telescope observations 

As telescopes become larger, with new ones that have mirrors exceeding 30 metres like the planned thirty-metre telescope or the Extremely Large Telescope,  they are able to detect extremely faint objects at the very edge of the observable universe. But these observations often take long exposure times, which leaves plenty of time for shiny satellites to pass overhead and leave their telltale bright streaks across the frame, sometimes obliterating the object under study. 

An artist’s rendering shows the Extremely Large Telescope in operation on Cerro Armazones in northern Chile. (ESO/L. Calçada)

Other telescopes have very wide fields of view, encompassing large swaths of the sky at once, which brings even more satellites into view. For comet and asteroid hunters, who are searching for new objects in space, they also show up as streaks across an image of the stars. Multiple streaks left by satellites will make it more difficult to determine what is natural and what is artificial, including spotting asteroids that could collide with the Earth.

While astronomers are annoyed at the addition of so many new objects to the night skies, they also appreciate the benefit of the improved communication these new satellite constellations will bring. So rather than propose an all out ban, they are calling for a few compromises that could make the situation better for all. 

One simple solution is to paint the satellites black so they don't reflect as much sunlight back to the ground. They could be placed in higher orbits so they move more slowly across the sky. But what the astronomers are calling for at this point is a dialogue between the scientific community and communications companies, so dark skies, like our forests and oceans, will be treated as a natural resource open to all for use, but also something precious to be preserved.