MIT physicist Justin Kasper talks about why he wants to set up a telescope on the Moon and how, if it wasn’t for NASA, he might never have considered a lunar site.
Mason Inman
Last month, NASA announced its strategy for sending astronauts back to the Moon by 2020. The Moon could be a way station for future Mars missions or the source of new natural resources or even the site for an extraterrestrial home.
But if Justin Kasper has his way, the Moon would be home to a new kind of telescope that could see the universe in a whole new light.
Kasper, a physicist at MIT’s Kavli Institute for Astrophysics and Space Research, is part of a team working on the plan, which he presented at the American Geophysical Union meeting in San Francisco last month. The proposed telescope would consist of an array of nearly 50 antennas, printed on a flexible material, to catch very low-frequency radio waves, 10 to 100 times lower in frequency than FM radio.
Other satellites on Earth and orbiting in space capture visible light, microwaves, and x-rays, but low-frequency radio waves remain largely unexplored. Kasper and his colleagues plan to submit a proposal to NASA to have their telescope included in one of the first missions to the Moon.
Kasper spoke with Nature Network Boston about why a telescope on the Moon is the best bet for obtaining the first good images using these wavelengths.
The idea for a telescope on the Moon came from an earlier plan that you and your colleagues had for an orbiting set of radio antennas, right?
Yes. For years, I’ve been working on an idea called SIRA, the Solar Imaging Radio Array.
But then suddenly, you have [NASA’s] Vision for Space Exploration: the thought that there’s going to be a return to the Moon. So we started thinking about this. And we realized: wait a minute—nobody really talked about the Moon as a place to build this thing.
Why build this array on the Moon rather than Earth?
It’s quieter there, because as far as we know there aren’t any lunar radio stations [whose signals could interfere]. You don’t have an ionosphere [the layer of charged particles surrounding the Earth that blocks low-frequency radio waves] to worry about, so you’re actually able to look at these low frequencies. You just need to get antennas into space to get past the limitations of the Earth’s surface.
So why not build an orbiting version?
It has to be easier to design a system when an astronaut can kick it into place than to design 16 satellites that deploy autonomously. Another challenge is the fuel you consume to maintain the constellation [of satellites]. On the lunar surface, it can just sit there.
The nice thing about the Moon being tidally locked with the Earth [so that the same side of the Moon is always facing Earth] is that you just have the astronaut point the dish towards Earth [to send signals back to Earth] and then they’re done. There are no moving parts, no upkeep.
We think that it might actually be a lot easier to do this on the lunar surface—which kind of came as a surprise. It’s hilarious that we could have collectively forgotten about the Moon the way we did.
What would you learn from a low-frequency radio wave telescope that you can’t from other telescopes?
There is just an unexplored universe out there. Even with a simple array, we could make a crude map of the universe at these lower frequencies.
We could look at, for instance, very old remnants of supernovas that we can’t detect with Chandra [an x-ray telescope on a satellite]. They’re way too cool to be giving off x-rays, and they’ve cooled off so much you don’t even see them in the normal radio emission.
We can also study the Sun. Maybe we can even help predict and alert astronauts if there are [solar] storms [which could hurt astronauts and damage their equipment].
What’s your group’s plan for making the array of antennas?
The idea is to use a sheet of insulating material, like Kapton. Kapton is like tape, but a better insulator and much more rugged, and you can manufacture this stuff extremely thin. So the idea is to deposit aluminum vapor on the Kapton. That is, you actually print the antennas directly on the Kapton. It’s like printing an electronic circuit, except that it is flexible.
Once you’ve done that, you just roll up the Kapton sheet, stick, say, three of these rolls on a box on a lander, and then just unroll them on the Moon’s surface.
How big would rolls be?
They would be about one meter wide and about 500 meters long when unrolled. Rolled up, they would be tens of centimeters across.
How would astronauts help out?
By doing the unrolling and deployment. In the simplest scenario, they would unroll this thing and make sure they don’t cut it on a boulder.
How does this fit with what NASA has envisioned for missions to the Moon?
I think this actually fits in very well. The reasons you would do science at the Moon are to understand the Moon, to help astronauts explore and survive on the lunar surface, to learn more about the solar system, and to learn more about the universe. And this is a device that we’ve come up with that hits all of those goals.