Abstract: An irrigation system that controls the amount of water to be applied based upon specific historical meteorological data including relative humidity, evapotranspiration data, and precipitation. The invention is also of a method for determining the optimal time of day to measure actual relative humidity, and for setting the relative humidity set-point.

Abstract: An air-deliverable, ice-penetrating sonobuoy vehicle has three-parts--a ptrator, instrument compartment, and antenna sphere. The parts are connected by frangible couplings which allow separation of the parts upon impact with the surface. The penetrator has a biconic nose-tip which forms a cavity in the ice, having a diameter only slightly larger than the diameter of the penetrator. When the larger diameter instrument compartment contacts the surface, frontal loadings will sever a frangible joint and thereby separate the penetrator from the instrument compartment. The antenna sphere, which has an even larger diameter, will separate from the instrument compartment in a like manner, except for an electrical connection. The antenna shpere has an eccentric ballast and will remain on the surface, transmitting signals from a hydrophone which is automatically released from the instrument compartment. The sonobuoy can also be used in open water.