Astronomy on the run
“We use hydrogen to map the distribution of matter in space,” says Gyula Jozsa. “When it’s resting, it emits signals at 1400 megahertz.” This is a protected band, but: “If we want to observe distant hydrogen, it’s redshifted. That means its frequency decreases and then we get into bands that are already occupied.”
The problem is getting bigger since more and more satellites are placed in low earth orbits, keyword: megaconstellations like Starlink from the US company SpaceX. “When satellites were mostly in geostationary orbit, radio interference was pretty static because the satellites didn’t move in the sky. An Excel spreadsheet was enough to solve the problem of not crossing anyone,” says Alexandre Vallet. This also applied to radio astronomy: Observations in unprotected frequency bands were always possible when no satellite was flying over the terrestrial radio telescope.
As optical light pollution got worse and we turned night into bright day, astronomers have moved to the most remote places on earth. They now build their telescopes on extinct volcanoes or in the Atacama Desert of Chile. But now, especially with the mega-constellations with their satellite internet, it’s about covering such remote regions as well.
»There are still some regions, for example in deserts, where there is little commercial interest in covering these areas as well. But I would say the problem of radio interference is much more complicated for radio astronomy than light pollution,” says Alexandre Vallet.
To the moon!
In this case, radio astronomy may have only one choice: the flight upwards. “If the moon didn’t exist, we would have to build it,” says Jack Burns of the University of Colorado. “On its far side there is no radio interference from Earth because the moon itself absorbs all radiation. There is no rain, no weather, no growing plants. Nothing changes on the moon. It’s the perfect spot for a radio telescope.”
In fact, Jack Burns will send a radio telescope to the moon later this year. It’s called ROLSES and will fly to the moon with one of the first commercial missions by the US company Intuitive Machines. Destination: the Vallis Schröteri of the lunar plane Oceanus Procellarum. Among other things, ROLSES is intended to be a kind of technology demonstration and to find out whether such antennas in much larger numbers on the far side of the moon could make a truly impressive telescope.