Half a Century Ago, Satellites Began to Obstruct Astronomers' Cosmic Observations

Satellites hampering radio astronomy — Science News, October 5, 1974

In the past, the satellites and probes launched by NASA and others successfully avoided conflict with the radio frequency bands reserved for radio astronomy. But now there is trouble.

The trespassers are two major U.S. satellites launched in May…. When either of the satellites is on or near the line between an observer and what he wants to study, the work is rendered difficult or impossible… radio astronomers may be able to live with one or two such interlopers. Twenty or a hundred would be a catastrophe for radio astronomy.

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The conflict between astronomers and satellites has only gotten worse. Private companies have launched thousands of new satellites since 2019 alone, far outstripping what astronomers thought would be catastrophic in the ’70s (SN: 3/12/20). As of September, there are upwards of 10,000 active satellites in Earth’s orbit, and private companies continue to launch more (SN: 4/8/23, p. 5).

Astronomers are worried that catastrophe is imminent, in part because many modern satellites emit a lot more radiation than previously thought (SN: 9/30/24). Optical telescopes are also now affected: The satellites leave bright streaks across images of the night sky, making the images difficult to analyze. Efforts to mitigate the problem by modifying the satellites or their orbits have had mixed results (SN: 10/9/21 & 10/23/21, p. 14).