The ACE satellite was launched August 25, 1997 by NASA. The satellite moves around the Lagrange point (L1) where the gravity of the sun balances with that of the earth. It observes the solar wind, which blows from the sun. The solar wind which passes the Lagrange point reaches the earth in 1 hour.
Disturbances in the solar wind cause variations in the space environment near the earth. For example, they can break an equipment on an artificial satellite and change the direction of the satellite. We NICT are receiving data from the ACE satellite cooperating with NOAA Space Weather Prediction Center in USA to advance `space weather forecast', which is a forecast of the space environment caused by the solar wind variation.
We are receiving data from the ACE satellite near the Lagrange point which is located 1,500,000 km far from the earth through our 11-m parabola antenna.