The Death of Astronomy?
The Death of Astronomy?
Probably not, but forthcoming commercial satellite constellations herald a new era for our night skies
By Caleb A. Scharf on May 27, 2019
Credit: European Southern Observatory
SpaceX's recent launch of 60 low-earth orbit satellites is just the start of a program to deploy thousands of relatively small, smart, and potentially disruptive devices for supplying broadband internet to many of the 3.8 billion humans currently lacking that utility. But astronomers have been quick to express concern about what these endlessly moving, sometimes bright constellations will do for anyone hoping to study or simply experience the night sky and the cosmos beyond.
What exactly is going on?
Several commercial entities are aiming to fill a huge gap in human data access (affecting about half our species' population) by launching a new generation of orbital broadband satellites. SpaceX is perhaps the most ambitious, with a final goal of some 12,000 'Starlink' satellites in different orbital 'shells', providing uninterrupted, high speed data to pretty much anywhere on the planet. But Amazon is not too far behind with its Project Kuiper and some 3,000 satellites, and others like OneWeb and what might eventually be 650 satellites.
Why so many satellites?
A few reasons are cost, coverage, and latency. In principle you could put up more geostationary satellites at 42,000 kilometer altitudes but these are hugely expensive, require highly directional, line-of-sight ground receivers and more powerful transmitters, and because of the finite speed of light there is an unavoidable time delay to each and every digital transaction. Alternatively, lots of low-orbit data-linked satellites can provide a dynamic 'dome-like' presence in the sky, more cheaply, and with much less time delay when some of them are not much more than a few hundred miles away from you at any moment.
What's bad for astronomy?
Short of being painted in Vantablack (which is not necessarily possible because of thermal regulation challenges in spacecraft) any artificial object will at times reflect sunlight down to the ground. This means that during portions of (early and late) night on Earth, overhead satellites hundreds of miles up can still be in daylight and appear as brilliant points of light streaking across the sky. For astronomers trying to capture deep exposure images or spectra of faint cosmic phenomena a bright satellite trail in the field of view can basically wreck the data. Other projects like the LSST plan on exploring the time domain of the cosmos - repeatedly imaging the sky night after night. Glinting, moving satellites get in the way of that. And for radio astronomy, which can seek to explore the universe in microwave bands, any satellite communications (often in similar if not overlapping frequencies) are yet another source of disastrous noise in an already noisy technosphere.
More:
https://blogs.scientificamerican.com/life-unbounded/the-death-of-astronomy/
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