50 years ago, satellites threatened astronomers’ view of the cosmos

Satellites interfere with radio astronomy – Scientific news, October 5, 1974

In the past, 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 offenders are two large US satellites launched in May…. When either satellite is on or near the line between an observer and what he wants to study, the job becomes difficult or impossible… radio astronomers may be able to live with one or two such interferometers. Twenty or a hundred would be a disaster for radio astronomy.

Update

The conflict between astronomers and satellites has only worsened. Private companies have launched thousands of new satellites since 2019 alone, far exceeding what astronomers thought would be disastrous in the 1970s (SN: 3/12/20). As of September, there are over 10,000 active satellites in Earth orbit, and private companies continue to launch more (SN: 4/8/23, p. 5).

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