Getting Data about the Solar System: Telescopes and Spacecrafts


By Sabine Stanley, Ph.D.Johns Hopkins University

There are two ways in which we can get data about things far away from the Earth—using telescopes and with spacecrafts. Let’s take a look at the potential developments in these two areas.

The Hubble Space Telescope as seen from the departing Space Shuttle Atlantis.
Telescopes of all kinds are used to collect data about faraway regions of our solar system and beyond. (Image: NASA/Public domain)

Telescopic View: Space and Earth

Our study of the solar system and the universe changed when Hubble was launched in 1990 and successfully repaired and upgraded in 1993. Hubble’s large mirror is 2.4 meters in diameter. That, combined with the fact that the telescope operates in space, where the Earth’s atmosphere can’t cause any problems, are the important factors in the science revolution that Hubble brought forth.

With Hubble, we’ve been able to monitor the planets in our solar system, especially at times when spacecraft aren’t visiting them for even closer views. With Hubble we’ve captured pictures of global dust storms on Mars, new storms on Neptune, and even volcanoes on Io. Hubble can also be used to study the atmospheres of extrasolar planets.

The successor space telescope to Hubble is the James Webb Space Telescope, or JWST for short. This telescope’s mirror is 6.5 meters in diameter. The mirror is actually a set of smaller hexagonal mirrors grouped together in a honeycomb fashion to produce a light collecting area that’s over 6 times larger than Hubble’s mirror. That means it will be able to see things that are much fainter.

Telescopes from Earth are also getting much better, including the Giant Magellan Telescope (GMT), which should be able to see oxygen molecules in the atmospheres of exoplanets. And there’s the Extremely Large Telescope (ELT), whose 39-meter mirror should let us image rocky exoplanets. But beyond all that, what might be the next big thing in telescopes?

This is a transcript from the video series A Field Guide to the PlanetsWatch it now, on The Great Courses Plus.

Moon-based Telescopes

We could put a telescope on the Moon. And instead of trying to engineer a really smooth and accurately-shaped solid mirror, one idea involves a liquid mirror telescope.

We have liquid mirror telescopes on Earth. They’re made with mercury that stays molten at room temperature and reflects light very efficiently. By using a spinning container, the surface of the liquid can be given a parabolic shape needed for the lens.

On the Moon, we’d need liquids that stay liquid at cold lunar temperatures, and are also stable against evaporation even in the lunar vacuum. The mirror could sit at the bottom of a lunar crater and perhaps be as large as 100 meters in diameter.

Learn more about humans on the Moon.

Radio Telescopes on the Moon

Another appealing possibility for Moon telescopes would be to put a radio telescope on the far side of the Moon. Why the far side? Because then the telescope would be shielded from all the radio emissions from Earth!

The 100 meter Green Bank Telescope, Green Bank, West Virginia, US.
Radio telescopes on the Moon will be able to operate without interference from the radio waves on Earth. (Image: Geremia/Public domain)

You could build the radio telescope from millions of small radio antennas, scattered over a region of about 100 square kilometers. Such a radio telescope could be used to study radio emissions from aurora around other planets, perhaps even exoplanets!

This could therefore be a way to detect magnetic fields from exoplanets, and give us a better idea which planets are truly habitable. And if any such planet harbors an alien civilization, a Moon-based radio telescope would be a way to detect any radio wave signals they might be emitting.

Using Spacecrafts to Collect Planetary Data

But we can collect even more information by visiting places in the solar system. So, how can we collect more and better data at any worlds we visit? What are the next big ideas for how to design a spacecraft?

Flight hardware of Mars Cube One (MarCO) (folded up).
The tiny MarCO cubes that flew to Mars to monitor the lander proved that small spacecraft could be successful in doing space research. (Image: NASA/JPL-Caltech/Public domain)

One big idea is to develop low-flying airplanes or copters or balloons to explore planets. Like the Mars helicopter technology demonstration on the Mars 2020 rover, or the dual-quadcopter DragonFly mission proposal for Saturn’s moon Titan.

Another big idea is to go with lots of small spacecraft. Just land many really small spacecraft all over the surface to take measurements. The first technology demonstration that such small spacecraft could fly to far locations and have their instruments work properly were the MarCO CubeSats that flew to Mars alongside the Mars InSight spacecraft. They helped monitor the InSight Lander’s trajectory near orbit insertion in 2018.

Exploring Oceans on Other Worlds

But for places under the surface of planets, like the subsurface oceans on outer solar system icy moons like Europa and Enceladus, we will need different ideas. How about a submarine on Europa? The first hurdle to overcome would be getting the submarine down to the subsurface ocean. That means somehow getting through around 10–25 kilometers of solid ice.

Prototypes of heat-powered drills have been proposed that could melt down through the ice, slowly descending the submarine to the subsurface ocean. One futuristic idea is a buoyant rover. NASA JPL scientists have traveled to the Arctic to test a rover that drives on the underside of the solid ice in the frozen ocean.

Learn more about exploring Mars from space and the ground.

Samples from Other Planets

And of course another way to explore planets is to bring the planets to us. Or at least, samples from other planets. The Apollo mission samples changed our understanding of the Moon, of Earth, and the rest of the solar system. Being able to use lunar samples to figure out chronologies in the solar system has been crucial to understanding solar system evolution. And the ability to analyze samples of planetary bodies in laboratories on Earth allows a level of science not possible by sending spacecraft to other planets to do analysis in the field.

Some missions are already underway. For example, the OSIRIS-REx mission will return a sample from the near-Earth asteroid Bennu to Earth in 2023. The sample will be collected by landing on Bennu for a few seconds, spraying the surface with nitrogen gas to uplift surface material, and collect the material in a chamber for return to Earth. There are also several mission concepts for a Mars sample return, perhaps in the 2030s.

We are truly on our way to investigate the mysteries of the universe.

Common Questions about Getting Data about the Solar System: Telescopes and Spacecrafts

Q: Why are telescopes in space better than telescopes on Earth?

The fact that a space telescope, like the Hubble Space Telescope operates in space, where the Earth’s atmosphere can’t cause any problems, makes them better.

Q: Why would it be best for lunar radio telescopes to be located on the far side of the Moon rather than its near side?

It would be ideal to put a radio telescope on the far side of the Moon. This way, the telescope would be shielded from all the radio emissions from Earth.

Q: Why is it a good idea to send many small spacecraft to get samples, rather than just one big one?

Sending many small spacecraft for space exploration is a good idea because then they can be spread all over the surface of another planet to take measurements.

Q: Which is the first mission that will attempt to return samples from a asteroid back to Earth?

The OSIRIS-REx mission will return a sample from the near-Earth asteroid Bennu to Earth in 2023. The idea is to land on Bennu for a few seconds, spray the surface with nitrogen gas to uplift surface material and collect the material in a chamber for return to Earth.

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