Replace the Arecibo radio telescope with one on the moon’s far side

The iconic Arecibo radio telescope in Puerto Rico, which has been making scientific discoveries for 57 years, not to mention serving as the backdrop of such films as Contact and Goldeneye, has collapsed. The radio observatory had already been slated for decommissioning when two cables snapped and it was judged too dangerous to repair. Now the Arecibo is little but rubble.

To say that the Arecibo telescope’s loss is a blow to science puts the matter mildly. The radio telescope was not only used for radio astronomy of distant objects, but also for the detection and characterization of Near-Earth Objects (NEAs), asteroids and comets that occasionally pass close to the Earth. It was also used to search for alien signals as part of the Search for Extraterrestrial Intelligence (SETI). Arecibo was once the largest observatory of its time, surpassed only in 2016 by the Five Hundred Meter Aperture Spherical Telescope (FAST) in China.

As scientists and fans of astronomy sadly contemplate Arecibo’s wreckage, some have begun to wonder if an effort should be made to replace it. The suggestion in turn points one to a NASA proposal to build a radio observatory on the moon’s far side.

Just as the Arecibo was built in a natural sinkhole, the far side radio observatory would be built in an existing crater. The Lunar Crater Radio Telescope (LCRT) would have a number of advantages over any similar Earth-bound observatory. It could observe the universe in wavelengths that are reflected by the Earth’s atmosphere. The LCRT would also be shielded from the Earth’s radio noise by the moon’s mass. At a kilometer in diameter, the lunar-based observatory would dwarf both the Arecibo and the Chinese FAST.

The need for a new radio telescope and the advantages of building on the lunar surface coincide with the United States, and a coalition of international and commercial partners, proposing to return to the moon as early as 2024. Joseph Silk, a professor of Astronomy at Johns Hopkins University, noted in a paper in the journal Nature that the return of humans to the moon, this time to stay, constitutes a rare opportunity to advance the science of radio astronomy. Silk suggests a slightly grander design than a simple dish stuck in a crater.

“A radio array able to capture these data would probably use millions of simple radio antennas deployed over an area a hundred kilomet[er]s across on the Moon’s far side, operated by humans and robots. Infrared telescopes of unprecedented scale could be built in cold craters near the lunar south pole, in permanent shadow where temperatures as low as 30 kelvin have been measured. With no atmosphere to absorb radiation and block signals, Moon-based scopes could yield fantastic images of exoplanets and the oldest galaxies in the Universe.“

Silk goes on to suggest that the cost of his scheme would be about 5 percent of the other planned lunar operations. Thus far, though, NASA has offered no specific plans to do lunar-based astronomy.

The lunar base contemplated by NASA’s Artemis Project would be a community of scientists, business entrepreneurs and others devoted to research, commerce and international cooperation. The outpost could be used as a base to build and then operate the far side lunar observatory. If we’re returning to the moon anyway, it would behoove us to take advantage of the opportunity to delve into the secrets of the universe as never before.

The opportunity comes at a time when presidential administrations are scheduled to change. Project Artemis is a President Donald Trump initiative. Understandably, some wonder if the incoming Biden administration may decide to cancel the project, just as President Obama terminated President George W. Bush’s Constellation return to the moon program. The opportunities that a return to the moon represents, including the advancement of radio astronomy, would argue against such a precipitous and unwarranted move.

Mark Whittington, who writes frequently about space and politics, has published a political study of space exploration entitled Why is It So Hard to Go Back to the Moon? as well as “The Moon, Mars and Beyond.” He blogs at Curmudgeons Corner.  He is published in the Wall Street Journal, Forbes, The Hill, USA Today, the LA Times and the Washington Post, among other venues.