Dark Ages Radio Explorer (DARE)
The Dark Ages Radio Explorer (DARE) mission is a proposed concept lunar orbiter intended to identify redshifted emanations from primeval hydrogen atoms just as the first stars began to emit light. DARE will use the precisely redshifted 21-cm transition line from neutral hydrogen (1420.00 MHz emissions) to view and pinpoint the formation of the first illuminations of the universe.
Also, this is the period ending the Dark Ages of the universe. The orbiter will explore the universe as it was from around 80 million years to 420 million years after the Big Bang. The mission will deliver data pertaining to the formation of the first stars, the initial black hole accretions, and the reionization of the universe. Computer models of galaxy formation will also be tested.
This mission might also add to research on dark matter decay. The DARE program will also provide insight for developing and deploying lunar surface telescopes that add to refined exoplanet exploration of nearby stars. It is expected to launch in either 2021 or 2022.
The period after recombination occurred and before stars and galaxies formed is known as the "dark ages". During this time, the majority of matter in the universe is neutral hydrogen. This hydrogen has yet to be observed, but there are experiments underway to detect the hydrogen line produced during this era. The hydrogen line is produced when an electron in a neutral hydrogen atom is excited to a state where the electron and proton have aligned spins, or de-excited as the electron and proton spins go from being aligned to anti-aligned. The energy difference between these two hyperfine states is electron volts, with a wavelength of 21 centimeters. At times when neutral hydrogen is in thermodynamic equilibrium with the photons in the cosmic microwave background (CMB), the neutral hydrogen and CMB are said to be "coupled", and the hydrogen line is not observable. It is only when the two temperatures differ, or decoupled, that the hydrogen line can be observed.
...
Wikipedia