21 cm Spectroscopy with the Upgraded Arecibo Telescope

The recent upgrade of the Arecibo radio telescope included a Gregorian reflector system, an expanded suite of receivers and a flexible new auto/cross-correlation spectrometer. The resulting improved sensitivity and expanded frequency range available have led to greater capability in observing gas in galaxies. The frequency agility and the advanced features of the correlator allow a broad range of redshift space to be sampled simultaneously. Also, highly redshifted emission (and absorption) from the gas in galaxies can now be observed. However, the radio frequency interference environment imposes constraints on these observations. The specifications of the current system are discussed.