Galactic All-sky Survey

The Galactic All-sky Survey (GASS) was a survey of HI emissions throughout the Milky Way. It covered all the (southern) sky below a declination of +1° with an angular resolution of 16 arcminutes. It observed the 21-cm line of neutral hydrogen, recording wavelength deviations interpreted as Doppler shifts due to radial velocity of the gas. As such, it covered moving HI regions with local standard of rest velocities in the range of -400 km/s to +500 km/s with a resolution of 1 km/s. Observations were made in 2005-2006 on the Parkes Observatory in New South Wales, Australia, and data was released in 2009.

For the northern sky, the surveys, GALFA-HI (Galactic Arecibo L-Band Feed Array HI Survey, using Arecibo Observatory) and EBHIS (Effelsberg-Bonn HI Survey, using the Effelsberg 100-m Radio Telescope) have gathered analogous data.

Note that the acronym GASS is also used for the GALEX Arecibo SDSS Survey.