American Scientist

Cosmologists are seeking the Dark Ages signal, radio waves emitted by hydrogen atoms during the mysterious era after the Big Bang but before the first stars lit up. Detecting the Dark Ages signal could help answer some of the biggest questions in cosmology, such as the nature of dark energy and the origin of the large-scale structure. LuSEE-Night (the Lunar Surface Electromagnetics Experiment-Night) is a pathfinder radio telescope that will operate on the farside of the Moon—studying the universe from a previously inaccessible location, at a frequency range that has never before been observable.

Drowning in Noise

Radio waves from the Dark Ages cannot be measured from Earth because the atmosphere absorbs and reflects them before they reach the ground. Such signals would also be drowned out by noise from our ubiquitous radio communications and other electronics.

Finding a Quiet Sky

On the lunar farside, LuSEE-Night will use the Moon as a shield to block radio interference from Earth. Hydrogen emission has a natural frequency of 1.42 gigahertz. Due to the expansion of the universe, the Dark Ages signal will show up at a much lower band, between 0.1 and 50 megahertz.

Landing Target

28.8 degrees south, 182.2 degrees east
A relatively high-altitude location on the Moon’s southern hemisphere provides a good view of the radio sky, along with favorable access to an orbiting relay satellite.

Radio Silence

A commercial Blue Ghost lander operated by Firefly Aerospace is scheduled to deliver LuSEE-Night to the surface of the Moon next year. Because a radio-quiet environment is crucial, all other parts of the lander will shut down at the end of the first lunar day, and LuSEE-Night’s electronics will be fully shielded.

Antennas Out

Four 3-meter-long, self-deploying radio antennas rotate via a motorized turntable atop the Blue Ghost craft. The Dark Ages signal is expected to be the same in all directions, so any radio noise that changes after antenna rotation can be filtered out.

An Extreme Environment

LuSEE-Night will make observations during lunar night, when temperatures drop to -175 degrees Celsius. Then it must tolerate 120 degree heat during the day, when it will recharge its onboard batteries. The mission is designed to operate for one year, which will require surviving a dozen lunar day–night cycles.

Heart of the Experiment

The heart of LuSEE-Night is its radio spectrometer, a device that can simultaneously tune in to multiple frequencies of radio waves, from 0.1 to 50 megahertz, collected by the telescope’s antennas. Measuring the frequency and intensity of that cosmic radio emission will eventually allow researchers to map the temperature and distribution of hydrogen gas during the Dark Ages. The lower the detected frequency, the further we are seeing back in time toward the Big Bang.