Wind, together with its sister spacecraft Polar, is NASA's contribution to the International Solar Terrestrial Program (ISTP), an international effort to quantify the effects of solar energy on Earth's magnetic field. From an L-1 halo orbit, Wind provides continuous measurement of the solar wind, particularly charged particles and magnetic field data and thus helps show how the solar wind affects magnetospheric and ionospheric behavior. It also carries the first Russian instrument to fly on an American spacecraft since cooperation in space between the two countries resumed in 1987.