While not an official full-fledged NASA mission, the concept of the Lunar Crater Radio Telescope, or LCRT, has been in development for years. The project recently received a $500,000 boost upon entering the second phase of NASA’s Innovative Advanced Concepts program.
The lunar telescope would involve robots hanging wire mesh within a crater on the moon’s far side to create a radio telescope. Picture the famed yet now defunct Arecibo Observatory in Puerto Rico, but on the moon.
The telescope could measure radio waves from a few hundred million years after the Big Bang that created our universe, before the first stars ever appeared.
The details of this chapter in the history of our universe have eluded cosmologists, and these radio waves could reveal what happened during that time.
“While there were no stars, there was ample hydrogen during the universe’s Dark Ages — hydrogen that would eventually serve as the raw material for the first stars,” said Joseph Lazio, LCRT team member and radio astronomer at NASA’s Jet Propulsion Laboratory in Pasadena, California, in a statement.
“With a sufficiently large radio telescope off Earth, we could track the processes that would lead to the formation of the first stars, maybe even find clues to the nature of dark matter.”
Projects like LCRT are selected by the program during a peer-review process of assessing proposals for missions that would further our understanding and exploration of space. It’s early days for this telescope, which could require years of technology development, but this approach fuels NASA’s selection of future missions.
“Creativity is key to future space exploration, and fostering revolutionary ideas today that may sound outlandish will prepare us for new missions and fresh exploration approaches in the coming decades,” said Jim Reuter, associate administrator for NASA’s Space Technology Mission Directorate, in a statement.
The far side of the moon
The radio telescopes scientists use on Earth can’t assess the radio waves from this cosmic era because they’re blocked by the ionosphere, which are the charged particles in our planet’s upper atmosphere. Earth is also full of its own radio emissions that can prevent faint signals from being tracked by radio astronomy.
The far side of the moon, where only robots have ever tread, is an atmosphere-less and perfectly quiet place — which would prevent any radio interference from Earth.
“Radio telescopes on Earth cannot see cosmic radio waves at about 33 feet (10 meters) or longer because of our ionosphere, so there’s a whole region of the universe that we simply cannot see,” said Saptarshi Bandyopadhyay, lead researcher for LCRT and a robotics technologist at JPL, in a statement. “But previous ideas of building a radio antenna on the Moon have been very resource intensive and complicated, so we were compelled to come up with something different.”
The larger the radio telescope, the better the sensitivity for tracking long radio wavelengths.
A crater stretching over 2 miles (3 kilometers) wide could host a radio telescope with an antenna over 0.5 mile (1 kilometer) wide.
For reference, Arecibo was 1,000 feet (305 meters) wide and the Five-hundred-meter Aperture Spherical Telescope (FAST) in China is 1,600 feet wide. Both were built inside natural depressions to support their bowl-shaped structures.
Within these bowls are thousands of reflective panels to make the entire dish receptive of radio waves. Suspended on cables above the dish is a receiver that can measure radio waves as they bounce off the bowl. Towers anchor the cables. Arecibo became inoperable after some of these cables and towers failed, crashing into the dish below and shattering the panels.
Robot construction team
Bandyopadhyay and his team want to streamline this to a more basic design that won’t require transporting heavy equipment to the moon.
Instead, robots could construct the dish using wire mesh overlaying the center of the crater. One spacecraft could transport the mesh from Earth to the moon while a separate lander would deliver rovers to build the dish.
These DuAxel rovers are a concept being developed at JPL. Two single-axle rovers can stay connected using a tether, but still undock from each other, with one serving as an anchor on the crater rim while another roams down to the crater floor for construction.
“DuAxel solves many of the problems associated with suspending such a large antenna inside a lunar crater,” said Patrick McGarey, LCRT and DuAxel team member and robotics technologist at JPL, in a statement. “Individual Axel rovers can drive into the crater while tethered, connect to the wires, apply tension, and lift the wires to suspend the antenna.”
The latest funding awarded to the team will help them identify challenges, target different approaches to the mission, and determine the capabilities of the telescope.
The first challenge is the actual design of the wire mesh. It will need to be strong and flexible enough to maintain shaping and spacing, but remain lightweight enough to be flown to the moon. And it will need to survive lunar surface temperature swings from minus 280 degrees Fahrenheit (minus 173 degrees Celsius) to 260 degrees Fahrenheit (127 degrees Celsius).
The team is also deciding if the rovers should be fully autonomous or if they will require a human operations team on Earth.
The researchers will work through these decisions over the next two years in the hopes that their project will be selected for future development.
“The development of this concept could produce some significant breakthroughs along the way, particularly for deployment technologies and the use of robots to build gigantic structures off Earth,” Bandyopadhyay said. “I’m proud to be working with this diverse team of experts who inspire the world to think of big ideas that can make groundbreaking discoveries about the universe we live in.”
Other projects operating under the Innovative Advanced Concepts program include a small spacecraft “swarm” that could study Venus’ atmosphere, a Pluto lander, asteroid-hunting spacecraft, fungi habitats and spacecraft that could explore the solar system and interstellar space.
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