Satellites are increasingly spoiling the view of the Hubble Space Telescope

An endless black sky, countless stars and a thick white streak. This is what the Hubble Space Telescope sees when another satellite flies over the image. Crowds in space are increasingly obstructing the telescope’s view, scientists wrote on Thursday Nature. The photos can then become unusable.

Hubble orbits the Earth at an altitude of more than 500 kilometers. This counts as a low job, where he gets busier and busier. For example, Starlink, the satellite network with which billionaire Elon Musk wants to provide internet to the world, already has 3,580 small spacecraft. This number could more than double. Other companies are working on similar networks.

Because Hubble looks at small areas of space where little light comes from, the telescope uses shutter speeds of several minutes. The longer the telescope collects the light, the more likely it is that a satellite will pass during that time. Satellites reflect sunlight and appear as a band in the photo.

About 2.7% of images between 2002 and 2021 contain such a band, the researchers write in Nature. But in 2021, the probability of a streak was 59-71% higher than in previous years, and that probability is expected to increase further.

Precious time

For now, this concerns only a small proportion of the photos with a negligible effect on scientific research. If the number of satellites continues to grow, academics foresee a problem. If 100,000 satellites are flying in orbit around the Earth, the probability of an image with a satellite band can reach 50%.

The closer a satellite flies to Hubble, the wider the orbit that appears in the photo. Those of artificial moons more than a thousand kilometers above the earth can still be extracted from the photos with software, but it is more difficult with Elon Musk’s low-flyers.

As a result, more and more Hubble images are becoming unusable. Taking more shots with a shorter shutter speed can counter this problem, the researchers write in Nature, but missed shots also waste time. That time is limited: For years, astronomers wondered how long the 1990 telescope would last.