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This is how Elon Musk can fix the damage his Starlink satellites cause for astronomy




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In all sectors of the economy or industry, it has always been the rule that you are when there is no law against it Protecting a resource gives you the freedom to use it or take as much of it as you want to achieve your own goals. Until regulatory action is taken, disruptors and innovators can self-regulate, often at the expense of those who do scarce resources were now dependent.

In astronomy, the greatest resource is a dark, clear night sky: the window of humanity to the universe Contain turbulent air, cloud cover and artificial Li pollution. More recently, a new kind of pollutant has begun to pose an existential threat to astronomy itself: mega constellations of satellites. If Elon Musk's Starlink project continues as it has begun, it will probably end astronomy on the ground as we know it.

The launch of satellites to provide services to those living on the ground is an integral part of modern life. GPS and telecommunications satellites enable our mobile signals and today support our mobile Internet. With the upcoming upgrade to 5G services, a new infrastructure will be required and this inevitably means that an updated set of satellites equipped for this service must be launched.

One of the first companies to try to serve this market is SpaceX, led by Elon Musk, who plans to deploy 12,000 satellites in a mega constellation called Starlink. Ultimately, the constellation hopes to expand to a total of 42,000 satellites. By November 20, 2019, only 122 of these satellites were deployed, and they have already had a negative impact on astronomy worldwide.

If we want to mitigate this, either the regulators or the executives of SpaceX will need it themselves

From Earth's darkest sky, about 9,000 stars are visible to the human eye: up to a visual magnitude of +6.5, the limit of human vision. The first 122 satellites launched by Starlink are not only brighter than most of these stars, they also move quickly across the sky, leaving tracks that pollute astronomers' data.

If these satellites were either weak, few or slow moving, this would only be a minor problem. If you only observe a narrow area of ​​the sky, you simply reject all the exposure frames (or even just the pixels of them) in which the disturbing objects roam the sky. However, with a large number of bright, fast-moving satellites, you will need to remove an exposure frame containing these artifacts, especially if you are looking for image-to-image changes (as is the case in many current and future observatories).

On November 18, 2019, a series of 19 of these Starlink satellites passed the site of the Cerro Tololo Inter-American Observatory in Chile, lasted more than 5 minutes and had a strong impact on the widefield DECam instrument which depicts a field 3 square degrees at an outstanding resolution of 0.263 arc-seconds per pixel.

Although this represents only 0.3% of the total number of proposed Starlink satellites that SpaceX would like to launch, the consequences are clear: far-field astronomy is designed to search for weak objects – main targets of observatories such as Pan-STARRS, LSST and any observational program aimed at finding potentially endangering objects – is severely hampered. Averaging over frames is not desirable because it is another important scientific goal of astronomers' ability to study the natural variability of objects. Because Starlink satellites change their orbits autonomously and are extremely noisy, ground-based observations can not be planned to avoid them.