5 Reasons Why Astronomy Is Better From The Ground Than In Space

When you think about what’s out there in the abyss of deep space, whether you’re looking out at the planets in our Solar System or the most distant galaxies perceptible in the Universe, the instrument most people think about using for the best images and data is the Hubble Space Telescope. Perched hundreds of miles above the Earth’s atmosphere, issues like clouds, atmospheric distortion, turbulent air, or even pollution are no concern. Images are as sharp as the cameras and optics on board allow, and from its position off-world, it can look in any direction we want it to. Using it, we’ve seen wonders the likes of which we’ve never imagined; Hubble has shown us what the Universe truly looks like.

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And yet, there are things we can do from the ground that are indisputably superior to anything we can do from space. There are images we can create and data we can collect that are simply impossible to do from space. Whether we’re using ground-based telescopes, balloon-borne observatories or even a high-altitude aircraft, there are many good reasons to remain here on Earth. Sure, flying above the atmosphere and receiving the omnidirectional perspective that going to space gives you are definite victories for the space telescope aficionados; there’s no way adaptive optics or a pristine observing site can compete with an observatory that doesn’t have the Earth to contend with. But there are some very compelling reasons to do astronomy on the ground, as there are benefits that you lose the instant you go to space. Here are the top five.

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1.) Space telescope technology is obsolete, even before it’s launched.

In order to launch a space telescope, you need to decide what you’re going to try to do with it, design-and-build your instruments, integrate them on board the observatory, and then launch it. For a mission like the James Webb Space Telescope, the design of its instruments was complete at the beginning of the decade; an instrument built today would have approximately seven years of superior technology integrated into it. Servicing a telescope in space is costly, risky, and in some cases (like when your telescope is out of reach of a crew-carrying spacecraft), practically impossible. But if your observatory is on the ground? Simply pop out the old instrument and pop in the new one, and your old telescope is state-of-the-art once again, to the limit of its optical design.

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2.) You can build a larger observatory on the ground than you can in space.

I can already hear your objection: that if you just spent enough money on it, you could launch as big a telescope as you wanted. That’s true, but only up to a point. Specifically, up to the point that your space-based observatory needs to fit into the rocket launching it! The Hubble Space Telescope is only 2.4 meters in diameter; the largest space telescope ever to fly is ESA’s Herschel, at 3.5 meters. James Webb will be bigger due to its segmented design, but each folded segment must fit aboard the rocket that will launch it. Even in NASA’s dreams, the LUVOIR space telescope concept tops out at 15.1 meters across. Yet on the ground, there are no neither size nor weight constraints, and three independent 30 meter-class telescopes are being designed and built: the GMTO, the ELT, and the TMT. In the radio, we can go even bigger, as facilities like Arecibo and FAST have demonstrated. In astronomy, size matters

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