Abstract

CHIME will use the 21cm emission line of neutral hydrogen to map large-scale
structure between redshifts of 0.8 and 2.5. By measuring BAO we will place
constraints on the dark energy equation of state as it begins to dominate the
expansion of the Universe, particularly at redshifts poorly probed by current
BAO surveys.

In this talk I will introduce CHIME, a transit radio interferometer designed
specifically for this purpose. I will discuss its goals and describe the
powerful new analysis techniques we have developed to confront the many
challenges of such observations, in particular removal of astrophysical
foregrounds which are six orders of magnitude larger than the 21cm signal. A
smaller 40m x 37m pathfinder telescope is currently operating at the DRAO in
Penticton, BC, and the construction of the full-sized 80m x 100m instrument
commenced in early 2015. I will report on current progress, and the lessons
already learned.