Sakigake

Sakigake, known before launch as MS-T5, was Japan first interplanetary spacecraft and the first deep space probe launched by any country other than the United States or the Soviet Union. It was built to demonstrate the performance of its new launch vehicle, test its ability to escape Earth gravity, and observe the interplanetary medium and magnetic field, and it also served as a reference probe for Halley Comet, with its early measurements intended to improve the later mission of the Suisei probe launched several months afterward.