DARK AGES RADIO EXPLORER (DARE)

[BjarneModerator Super Nova]

http://lunar.colorado.edu/dare/
Jeg omtalte denne mission på det gampe astro-forum, med et link til en rapport, men projektet er blevet langt mere interessant med den nylige opdagelse af en kraftig 21-cm absorption ved rødforskydningen z = 17.

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. 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 2 years, DARE observes at low radio-astronomy frequencies, 40-120 MHz, in a 125-km altitude lunar orbit. 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’s radiometer has a well-characterized spectral response, controlled systematics, and heritage from cosmic microwave background (CMB) missions and ground-based telescopes. 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 Mission Design: Low RFI Observations from a Low-Altitude Frozen Lunar Orbit

ABSTRACT: The Dark Ages Radio Experiment (DARE) seeks to study the cosmic Dark Ages approximately 80 to 420 million years after the Big Bang. Observations require truly quiet radio conditions, shielded from Sun and Earth electromagnetic (EM) emissions, on the far side of the Moon. DARE’s science orbit is a frozen orbit with respect to lunar gravitational perturbations. The altitude and orientation of the orbit remain nearly fixed indefinitely, maximizing science time without the need for maintenance. DARE’s observation targets avoid the galactic center and enable investigation of the universe’s first stars and galaxies.

 

Tidspunktet for dannelsen af de første stjerner er interessant ved, at det mørke stofs partikler på dette tidspunkt har den laveste hastighed i forhold til universets baryoner i form af hydrogen og helium. Der er herved en mulighed for at opdage en eventuel vekselvirkning mellem nogle eller alle mørke partikler og baryonerne. En sådan vekselvirkning giver sig til kende som en ekstra kraftig 21cm-absorption.

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