The Dark Ages Radio Explorer (DARE) will use the highly-redshifted hyperfine 21-cm transition from neutral hydrogen to track the formation of the first stars, black holes, and galaxies by their impact on the intergalactic medium during the end of the Dark Ages and during Cosmic Dawn (redshifts 11-35).
DARE supports the NASA Astrophysics goal, "Discover how the Universe works, explore how the Universe began and developed into its present form..." It also addresses "How did the Universe originate and evolve to produce the galaxies, stars, and planets we see today?" DARE will measure the sky-averaged spin temperature of neutral hydrogen at unexplored redshifts 11-35, providing the first evidence of the earliest objects to illuminate the cosmos and testing our models of galaxy formation. DARE's science objective addresses:
*When did the first stars form?
*When did the first accreting black holes form?
*When did the Hot Bubble Dominated Epoch and Reionization begin?
*What surprises do the end of the Dark Ages hold?
DARE will answer two fundamental questions identified in the recent Decadal Survey, New Worlds, New Horizons in Astronomy and Astrophysics: What were the first objects to light up the Universe, and when did they do it? The birth of the first stars and black holes is one of the truly transformative events in the history of the Universe. DARE's approach is to measure the spectral shape of the sky-averaged redshifted 21-cm signal from neutral hydrogen over the redshift range 11-35 (80-420 million years after the Big Bang), corresponding to radio frequencies 40-120 MHz.
DARE uniquely complements the efforts of the Wilkinson Microwave Anisotropy Probe (WMAP), the James Webb Space Telescope (JWST), and the Atacama Large Millimeter Array (ALMA) by bridging the nearly billion-year gap between the smooth Universe seen via the Cosmic Microwave Background and the rich web of galaxy structures imaged at more recent times.
These observations are challenging because the 21-cm signal strength is predicted to be much fainter than various foregrounds. However, DARE eliminates the most intense foreground, namely human-generated radio frequency interference (RFI). DARE orbits the Moon for a baseline mission of 3 years and takes data above the lunar farside, the only location in the inner solar system proven to be free of RFI. The smooth frequency response and differential radiometry of DARE are effective in removing the remaining foregrounds (i.e., the Galaxy and solar system objects).
This Mission draws on a rich intellectual and technological heritage from ground-based low frequency instruments as well as antennas, receivers, and S/C that have flown in similar space environments. They reflect the experiences, lessons-learned, and proven performance of EDGES, a ground-based pathfinder operating in Western Australia at higher frequencies. The DARE measurement strategy and science instrument design derives its intellectual heritage from EDGES. DARE is pioneering a new measurement from the lunar far-side, but it is not entering uncharted intellectual territory. The DARE strategy abandons the conventional absolute calibration requirement of a radiometer in favor of a differential spectral calibration requirement, an approach derived from EDGES (and analogous to differential radiometry used by WMAP).
DARE is led by Jack Burns, a highly-published scientist and successful large project and senior university administrator. The science team includes members who first modeled the global radio signal from the Cosmic Dawn, the PI of the ground-based DARE pathfinder (EDGES), and members with extensive flight mission experience. The team has decades of experience with centimeter and meter wavelength observations. The Project Manager at NASA Ames, the Spacecraft Project Manager at Ball Aerospace, and the Science Instrument Manager at JPL are seasoned veterans from multiple NASA space science missions.
DARE is led by Jack Burns, Professor of Astrophysics and Vice President Emeritus for Academic Affairs and Research for the University of Colorado. Burns is an elected Fellow of the AAAS and APS, and received NASA's Exceptional public Service Medal in 2010. The science team includes members who first modeled the global radio signal from the Cosmic Dawn, the PI of the ground-based DARE pathfinder (EDGES), and members with extensive flight mission experience. The team has decades of experience with centimeter and meter wavelength observations.