In the foothills of Colorado’s Rocky Mountain front range —- an area well known for cutting-edge space technology —- Jack Burns, a longtime astrophysics professor at the University of Colorado, Boulder —- may finally be seeing a decades-old vision of a low frequency lunar radio telescope coming to fruition.
Since the mid-1960s, Burns and colleagues have been saying that our Moon’s far side would make a perfect spot for low frequency radio astronomy.
“It’s the most radio quiet location in the inner solar system,” Burns told me in his Boulder office. In order to get this quiet, you would have to go all the way out to the equivalent orbit of Jupiter in order to reduce the amount of radio coming from Earth down to the same noise level it is on the Moon’s far side, he says.
But unlike previous initiatives to make a lunar far side telescope array a reality, this time commercial space technology’s accessibility has created a paradigm shift so that new space players like Jeff Bezos’ Blue Origin have expressed a strong interest in ferrying this telescopic array to the Moon . Whether this ambitious billion-dollar far side array will ultimately be funded by NASA or via a public partnership has yet to be determined, however.
Blue Origin would like NASA to fund them to bring our telescope but to the Moon, says Burns. But Bezos himself is interested in the science, Burns notes.
Although technology for the Farside Array for Radio Science Investigation of the Dark Ages and Exoplanets (FARSIDE) is already in place, the lunar lander itself still needs some finishing touches. Thus, FARSIDE isn’t expected to see first light on the lunar surface until 2030 at earliest.
When it does, the array will enable the precision measurement of the cosmos’ dark ages, before the birth of the first stars and before the formation of the earliest galactic structure. Operating well below the FM band in the frequency range between 10-40 MHz, FARSIDE would be capable of observing the cosmos when it was only 15 million to 80 million years old. Or less than a 100 million years after the big bang itself.
FARSIDE would consist of 128 pairs of dipole antennas emplaced robotically by four lunar rovers. Once the 10-km diameter array is set up, it would combine its signals electronically.
And in a single landing, Blue Origin’s Blue Moon lander would be large enough to bring everything the FARSIDE array would need. The array itself would extend from its center somewhat like a spiral wagon wheel in four cardinal directions from a southern equatorial flat plain.
Part of my research team is learning how to tele-operate these rovers from a distance; to deploy the instruments without getting all tangled up; and, to maneuver around rocks and craters, Burns, the FARSIDE array’s principal investigator, told me. A far side telecommunications satellite would relay the data back to Earth.
FARSIDE’s prime science goal will be studying highly redshifted primordial neutral hydrogen which lies in the radio spectrum’s 21-centimeter band. This will allow Burns and colleagues a radio peek at the earliest structure that such low frequencies allow.
The universe is expanding, so it stretches these wavelengths so that by the time they reach us they are in the tens to hundreds of meters in wavelength; that’s why it’s very low frequency, says Burns.
The early universe started off as a high energy soup of elementary particles – electrons and protons – following the big bang, says Burns. As the universe expanded, it cooled; eventually allowing electrons and protons to combine to form neutral hydrogen atoms, he notes.
Even though there were no stars yet, the cores of the cosmos’ first stars were forming and collapsing.
At roughly 100 to 200 million years the very first stars turned on; each some 100 times our Sun’s mass.
“The gravity affects the neutral hydrogen, so we will see the imprint of those first stars in the signals that we will observe with FARSIDE,” said Burns. We’re trying to understand how the very first stars and galaxies formed and how that pathway eventually led to us, he says.
Another major science goal for FARSIDE will be to look for coronal mass ejections and solar flares from nearby stars and measure their effects on their inner solar systems. If such systems harbor earthlike planets, the FARSIDE team will look for signs that such planets have global magnetic fields.
The reason we have life on our planet and Mars does not have obvious life on the surface is that we have a magnetic field and Mars does not, says Burns. Mars had one up until a few billion years ago and it shut down and the solar wind stripped the atmosphere and fried its surface, he says.
If an extrasolar planet lying in a given solar system’s so-called habitable zone doesn’t also have a global magnetic field, then its chances for life will be greatly diminished. Thus, one of the next steps in determining a nearby exo-Earth’s habitability quotient is finding out whether it currently harbors an existing magnetic field. To that end, FARSIDE will help.
FARSIDE will be capable of measuring the strength of magnetic fields around these planets, says Burns.
FARSIDE remains an observational lunar-based holy grail. But NASA and its commercial contractors have planned two lunar radio telescope precursor missions to prove both the science and technology necessary to make FARSIDE a reality.
The Radio wave Observations at the Lunar Surface of the photo‐Electron Sheath (ROLSES) will land on the lunar nearside later this year. And the Lunar Surface Electromagnetics Experiment (LuSEE) will make a far side landing in 2025.
“The Moon is now more accessible at a reasonable cost than ever before,” said Burns. “The technologies have advanced point to make it affordable.”
All we need is a lander, a lunar communications satellite and the funding, he says.