Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
GALEX Arecibo SDSS Survey (GASS) is a large targeted survey at Arecibo Observatory that has been underway since 2008 to measure the neutral hydrogen content of a representative sample of approximately 1000 massive galaxies selected using the Sloan Digital Sky Survey and GALEX imaging surveys. The telescope being used is the world's largest single-dish radio telescope and can receive signals from distant objects.