Many of the early instruments were research spacecraft that were re-purposed for space weather applications. One of the first of these was the IMP-8 (Interplanetary Monitoring Platform). It orbited the Earth at 35 Earth radii and observed the solar wind for two-thirds of its 12-day orbits from 1973 to 2006. Since the solar wind carries disturbances that affect the magnetosphere and ionosphere, IMP-8 demonstrated the utility of continuous solar wind monitoring. IMP-8 was followed by ISEE-3, which was placed near the Sun-Earth Lagrangian point, 235 Earth radii above the surface (about 1.5 million km, or 924,000 miles) and continuously monitored the solar wind from 1978 to 1982. The next spacecraft to monitor the solar wind at the point was WIND from 1994 to 1998. After April 1998, the WIND spacecraft orbit was changed to circle the Earth and occasionally pass the point. The NASA Advanced Composition Explorer has monitored the solar wind at the point from 1997 to present.
Many of the early instruments were research spacecraft that were re-purposed for space weather applications. One of the first of these was the IMP-8 (Interplanetary Monitoring Platform). It orbited the Earth at 35 Earth radii and observed the solar wind for two-thirds of its 12-day orbits from 1973 to 2006. Since the solar wind carries disturbances that affect the magnetosphere and ionosphere, IMP-8 demonstrated the utility of continuous solar wind monitoring. IMP-8 was followed by ISEE-3, which was placed near the Sun-Earth Lagrangian point, 235 Earth radii above the surface (about 1.5 million km, or 924,000 miles) and continuously monitored the solar wind from 1978 to 1982. The next spacecraft to monitor the solar wind at the point was WIND from 1994 to 1998. After April 1998, the WIND spacecraft orbit was changed to circle the Earth and occasionally pass the point. The NASA Advanced Composition Explorer has monitored the solar wind at the point from 1997 to present