HerS/HeLMS were designed to leverage the rich set of ancillary data in the SDSS Stripe 82, a rapidly expanding Legacy field, including: 

HETDEX: Spectroscopic Survey of LAEs at 1.8 < z < 3.5

ACT: Millimeter Survey imaging the CMB, CIB, and SZ effect

SpIES/SHELA: Spitzer-Warm IRAC Surveys

SDSS/BOSS: Spectroscopy and Imaging in the Optical

VICS82: J+Ks imaging over 180 deg2 to Kz < 22

DES/HSC: Optical Imaging to g ~ 25.3 mag

IRAS/WISE: far/near-infrared full-sky surveys

GASS: 21-cm Survey of the full southern sky

HerS/HeLMS add submillimeter maps, at 250, 350, and 500μm, to this data set.  These bands are sensitive to far-infrared emission from dusty star-forming galaxies and AGN from intermediate, high, and very high redshifts.  IR-emission, as a direct tracer of star-formation, is a sensitive probe of the star-formation history of the Universe; and in concert with existing ancillary data, can identify the populations responsible for the extragalactic background light.