A Japanese satellite (known as EXOS-D before it achieved Earth orbit) developed by the Institute of Space and Astronautical Science as the fourth in a series of satellites designed to study Earth’s aurora and magnetosphere. The 295-kg satellite was launched by a Mu rocket from Kagoshima Space Center on 22 February 1989. It had eight sets of instruments for scientific observation and was the first satellite to have anti-radiation technology applied to it. Akebono made important studies of aurorae and behavioural changes in Earth’s Van Allen radiation during the Sun’s 11-year solar cycle. After 26 years and two months of continuous observations, communications with the satellite terminated on 23 April 2015; the satellite lived well beyond its target life of one year.