LOFTI 2 ("LOw Frequency Trans Ionospheric Satellite", also styled LOFTI II) refers to a pair of United States Naval Research Laboratory satellites launched in 1962 and 1963 as a follow-on to the LOFTI-1 mission. The program's mission was to study how the ionosphere affected very low frequency transmissions. Both were 20-inch diameter aluminum spheres equipped with extendible antennas.[1]