The Dark Ages Radio Explorer (DARE) will probe the epoch of formation of the first stars, black holes, and galaxies, never before observed, using the redshifted hyperfine 21-cm transition from neutral hydrogen.聽
These first objects to illuminate the universe at the end of the dark ages into the cosmic dawn (redshifts 35 to 11) will be studied via their heating and ionization of the intergalactic medium. Over its lifetime of two聽years, DARE observes at low radio-astronomy frequencies, 40-120 MHz, in a 125聽km altitude lunar orbit.聽
The Moon occults both the Earth and the Sun as DARE makes observations above the lunar farside, shielding the spacecraft from the corrupting effects of radio interference, Earth's ionosphere, and solar emissions. A wideband dual bicone antenna, pilot tone stabilized polarimetric receivers to separate the unpolarized 21-cm signal from polarized instrumental and sky emission, and a digital spectrometer constitute the science instrument. DARE鈥檚 radiometer has a well-characterized spectral response, controlled systematics, and heritage from cosmic microwave background (CMB) missions and ground-based telescopes.聽
The unique frequency structure of the 21-cm signal and its uniformity over large angular scales are unlike the spectrally featureless, spatially varying characteristics of the galactic foreground, allowing the signal to be separated from the foreground. With a straightforward measurement, proven technology, and radio-quiet environs, DARE will open a new window of discovery into the early Universe.
DARE is a part of the聽Network for Exploration and Space Science (NESS), a聽multifaceted, multidisciplinary, and innovative investigation in the space sciences, including the areas of astrophysics and heliophysics that are enabled through human and robotic exploration of the target bodies.聽
One of the most important gaps in our understanding of our universe鈥檚 history is the cosmic dawn.聽The period from about 50 million years to one billion years after the Big Bang when the first stars, black holes, and galaxies in the universe formed. One of the best ways to observe this era is with low-frequency radio telescopes, which can observe the 鈥渟pin-flip鈥� radiation from the hydrogen that pervades the universe during the cosmic dawn. Astronomical observatories on the lunar surface and in cis-lunar space targeted at this background will be amongst the most sensitive probes of the early universe.聽