The epoch of the first stars and galaxies can be uniquely probed using the redshifted 21-cm transition of neutral hydrogen. This transition is sensitive to the thermal and ionization state of HI gas and thus provides a tracer of sources of energetic photons – primarily hot stars and accreting black holes - which ionize and heat the high redshift intergalactic medium. Sky-averaged spectra of the 21-cm background are expected to exhibit broad absorption and emission features relative to the microwave background at low radio frequencies. In this talk, I will describe the design of a lunar-orbiting experiment, the Dark Ages Radio Explorer (DARE), to detect the global spectral features at low radio astronomy frequencies (40-120 MHz, 11 < z < 35). Above the lunar farside, DARE avoids terrestrial radio frequency interference and ionospheric corruption. Since the 21-cm spectrum has broad spectral features whereas the foregrounds do not, the signal can be extracted through Bayesian methods including Markov Chain Monte Carlo techniques. The instrument, which consists of a dual-polarized wide-band dipole antenna, total power receiver, and digital spectrometer is calibrated using modeling and tone-injection techniques. Dynamic polarimetry is being studied as a way to measure the the foreground spectrum. With the current design specifications, signal-extraction pipeline, and observing strategy, DARE will place meaningful constraints on the Ly-α, Lyman continuum, and X-ray emissions of high redshift galaxies, along with the characteristic minimum mass of the first star-forming halos. -- ____________________________________________________ Richard F. Bradley, Ph.D. Scientist / Senior Research Engineer (NRAO) Research Professor of Astronomy (U. Virginia) Visiting Assistant Professor of EE (U. Virginia) Associate Editor: Radio Science Immediate Past Chair: Commission J U.S. National Committee of the National Academy of Sciences International Union of Radio Science (URSI) Vice Chair: Commission J International URSI