Explorer 7, launched 13 October 1959, was the last of the satellites developed for use during the International Geophysical Year. It was much heavier than its predecessor satellites and equipped with an extensive suite of experiments, with which it studied the Earth and the orbital environment during its year-and-a-half of operation in orbit. Perhaps Explorer 7's most significant achievement was an ongoing map of the Earth's radiation budget—the rate of planetary heating and cooling—thus inaugurating climate studies from orbit. Explorer 7 also returned a wealth of information on cosmic rays, Earth's ionosphere, and the Van Allen belts of radiation girdling the planet. Though the satellite was supposed to study the Sun in the X-Ray and Ultraviolet wavelengths, its sensors were saturated by radiation and returned no useful data.