From 1971 to 1976 Explorer was an integral part of the National Hail Research Experiment. Soviet investigators reported as much as 80% reduction in crop loss (Battan, 1969) by firing small rockets burning pyrotechnics embedded with lead iodide into building storms in the Alazani Valley in Georgia USSR. They attributed the success of their seeding efforts to the conversion to ice of large quantities of supercooled water in accumulation zones (up to 5 to 6 gm/m³) that they believed existed in the mature stages of thunderstorms in their region. Because of these claims, the Interdepartmental Committee on Atmospheric Sciences (US) requested that the National Science Foundation in consultation with other agencies develop a plan for establishing an expanded US program of hail suppression. NCAR was asked to conduct this program with the goal of simultaneously containing both research and randomized seeding experiments to evaluate the Russian model and their findings. This became known as the National Hail Research Experiment (NHRE).

The measurements made by aircraft in NHRE especially, the South Dakota School of Mines and Technology (SDSMT) T-28 aircraft (See the EOL Website for more information on the SDSMT T-28 aircraft) and Explorer showed that the large values of supercooled water thought to exist by the Russian scientists did not exist in the early or mature stages of storms of the high plains of Colorado. Explorer measurements also showed that coalescence was not active in the storms of NE Colorado. Combining results from the sailplane measurements made in NE Colorado during NHRE, in SE Montana during CCOPE and over Langmuir Laboratory in central New Mexico (read more here and here), Explorer observations demonstrated that precipitation formation in all three regions of the high plains was dominated by the ice process and by the formation of graupel.