Surveyor 6 was the fourth of the Surveyor series to successfully achieve a soft landing on the Moon. The primary objectives of the Surveyor program, a series of seven robotic lunar softlanding flights, were to support the coming crewed Apollo landings by: (1) developing and validating the technology for landing softly on the Moon; (2) providing data on the compatibility of the Apollo design with conditions encountered on the lunar surface; and (3) adding to the scientific knowledge of the Moon. The specific primary objectives for this mission were to perform a soft landing on the Moon in the Sinus Medii region and obtain postlanding television pictures of the lunar surface. The secondary objectives were to determine the relative abundance of the chemical elements in the lunar soil by operation of the alpha-scattering instrument, obtain touchdown dynamics data, obtain thermal and radar reflectivity data, and conduct a vernier-engine erosion experiment.

References
http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1967-112A