THE CANADIAN HYDROGEN INTENSITY MAPPING EXPERIMENT
CHIME is a new project, a novel radio telescope which relies on massive computational power instead of physically steerable dishes. It is composed of 5 cylinders, each 20m x 100m in size, which focus the feed patterns into long narrow primary beams running north-south. These are then interferometrically processed in a powerful digital correlator to yield a fan of 2560 "formed" beams, each with the full sensitivity of a 100m telescope. Earth rotation sweeps this fan across the sky, and CHIME surveys the entire northern celestial hemisphere each sidereal day.
The goal of this new instrument is to produce a vast 3-dimensional map of neutral hydrogen, by measuring the cosmologically redshifted 21cm radiation it emits. HI is a reasonable mass proxy, and can be used as a tracer for structure. Ultimately, CHIME is meant to detect the Baryon Acoustic Oscillations (BAO), the imprint left by acoustic waves propagating through the primordial plasma of the nascent Universe. The BAO manifest as a preferential separation scale in the Large Scale Structure (LSS), and by measuring the evolution of this scale over cosmic timescales, we can reconstruct the expansion history of the Universe.
CHIME is being built at the Dominion Radio Astrophysical Observatory (DRAO), near Penticton B.C. in Canada, and is a collaboration of several Canadian institutions: