Build Earth’s Largest Telescope Across the Moon

the Lunar crater radio telescope would provide a unique perspective on the early universe, even though it probably won’t be built for decades, according to NASA robotics engineer Saptarshi Bandyopadhyay, who is leading the project.

“We all want to know what happened. How did the universe evolve? What happened after the Big Bang?” Bandyopadhyay said Quirks & Quarks host Bob McDonald.

In the 14 billion years since that event, the light waves of that era have grown from tiny fractions of a millimeter to over 10 meters as the universe has expanded. These are now extremely long radio waves, and these cannot be seen on Earth “because the ionosphere is absorbing them,” Bandyopadhyay said.

“So we want to go somewhere far from [Earth] so that we can have a picture of the Big Bang and the evolution of the universe. ”

The size of the telescope presents challenges

The problem, however, is that in order to capture these wavelengths, not only does this telescope have to be on the moon, it has to be very large, which makes it difficult to build.

There are giant radio telescopes on Earth, which observe shorter radio wavelengths entering the atmosphere. The 300-meter-wide Arecibo telescope in Puerto Rico – recently demolished in a catastrophic accident – or the 500 meters wide FAST telescope in China represent significant engineering challenges.

Autonomous and self-supporting dish-shaped radio telescopes can only grow to a certain size, depending on the strength of the materials from which they are made and the need to withstand wind loads. To avoid these problems, the largest radio telescopes are integrated into the natural elements of the terrain. Arecibo and FAST, for example, were built in natural, dish-shaped sinkholes.

Building such a telescope on the moon is, in a sense, easier. The lower gravity on the moon means that a larger structure can be built with lighter materials. No atmosphere means no windstorms or other terrestrial environmental hazards, although there are challenges associated with the moon’s harsh temperatures.

According to Bandyopadhyay, the moon also has no shortage of appropriately shaped terrain structures in the form of ubiquitous impact craters.

“These craters appear to be natural places to set up this flat-shaped telescope because the crater also looks like a bowl.”

To find a candidate for the crater, Bandyopadhyay and his team combed through detailed photos taken by NASA’s Lunar Reconnaissance Orbiter and discovered more than 80,000 suitable craters on the other side of the moon.

Origami-inspired transport and construction

While the location would offer advantages, there are some unique and significant challenges to building on the moon, especially the harsh working conditions and the difficulty of transporting materials.

The team studied a range of scenarios for how a telescope could be built and transported to the moon. The one they arrived at was inspired by the folding of Japanese paper, Bandyopadhyay said.

“Origami is the art of folding paper into smaller, more interesting patterns. But in space, origami is widely used to take these large structures, like a mile-long big dish, and we can literally fold it a few times and make a nice little structure out of it.

The antenna would be built on Earth as a large, but extremely light, net-like structure made of conductive aluminum wire. It would be neatly folded in a package that would fit into the nose cone of a large rocket, possibly the space launch system that NASA is developing.

Once launched, the antenna would be transported to the moon and land on the bottom of the crater in which it would be installed. Then it should be deployed.

“We will have these robots that will come down … to the lander and then pull the lifting wires that will connect to the lander sitting at the bottom of the crater,” Bandyopadhyay said.

These lifting wires would be anchored to the rim of the crater and as they are moved up the antenna would unfold and unfold. Ultimately, the net-shaped antenna would be suspended above the bottom of the crater, looking a bit like a spider web in the shape of a dish.

The tension in the wires would be adjusted to give the proper dish shape to receive radio signals from space and reflect them back to a receiver.

All of this technology (with the possible exception of the launch rocket) is available today, Bandyopadhyay said.

Robots, for example, are currently being tested at NASA’s Jet Propulsion Laboratory.

“These robots are called DuAxel, and they’ve been actively built at JPL for over a decade now. And these robots have the unique feature of being able to descend almost steep terrain like sheer cliffs.”

For now, this is an early stage technical feasibility study, rather than a fully developed mission proposal, but Bandyopadhyay suggests it would certainly be expensive and be a high-profile endeavor for NASA.

“The cost is a big uncertainty right now. At the moment, all I can say is that we think it will be a flagship mission.”

Given that, it is likely that in decades, at least.

“Space is tough,” Bandyopadhyay said. “I would be surprised if I could see this launched and deployed before I retire, and I am a young scientist.”

Written and produced by Jim Lebans