[¦ərth ri¦sȯr·səz tek¦näl·ə·je ′sad·əl‚īt] (aerospace engineering) One of a series of satellites designed primarily to measure the natural resources of the earth; functions include mapping, cataloging water resources, surveying crops and forests, tracing sources of water and air pollution, identifying soil and rock formations, and acquiring oceanographic data. Abbreviated ERTS.AcronymsSeeERTS