Key Science Goals
Determine the neutral hydrogen (HI) content of galaxies over three-quarters of the sky, to measure how much intergalactic gas external galaxies are accreting; to search for dark, starless galaxies; to lay the foundation for SKA dark energy detection

Iam not your teacher you have to read yourself, they are searching for hydrogen and just frequencies near the frequency of hydrogen. If you have no idea about those stuff stopp missleading other people on the base of your ignorance.