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The redshifted 21-cm monopole is expected to be a powerful probe of the epochof the first stars and galaxies ($10<z<35$). The global 21-cm signal issensitive to the thermal and ionization state of hydrogen gas and thus providesa tracer of sources of energetic photons -- primarily hot stars and accretingblack holes -- which ionize and heat the high redshift intergalactic medium(IGM). This paper presents a strategy for observations of the global spectrumwith a realizable instrument placed in a low altitude lunar orbit, performingnight-time 40-120 MHz spectral observations, while on the farside to avoidterrestrial radio frequency interference, ionospheric corruption, and solarradio emissions. The frequency structure, uniformity over large scales, andunpolarized state of the redshifted 21-cm spectrum are distinct from thespectrally featureless, spatially-varying, and polarized emission from thebright foregrounds. This allows a clean separation between the primordialsignal and foregrounds. For signal extraction, we model the foreground,instrument, and 21-cm spectrum with eigenmodes calculated via Singular ValueDecomposition analyses. Using a Markov Chain Monte Carlo algorithm to explorethe parameter space defined by the coefficients associated with these modes, weillustrate how the spectrum can be measured and how astrophysical parameters(e.g., IGM properties, first star characteristics) can be constrained in thepresence of foregrounds using the Dark Ages Radio Explorer (DARE).

A Space-Based Observational Strategy for Characterizing the First Stars and Galaxies Using the Redshifted 21-cm Global Spectrum