Sakigake (さきがけ, lit.'pioneer', 'pathfinder'), known before launch as MS-T5, was Japan's first interplanetary spacecraft, and the first deep space probe to be launched by any country other than the USA or the Soviet Union. It aimed to demonstrate the performance of the new launch vehicle, test its ability to escape from Earth gravity, and observe the interplanetary medium and magnetic field. Sakigake was also supposed to act as a frame of reference for data received from probes that flew closer to Halley's Comet. Early measurements would be used to improve the mission of the Suisei probe launched several months later.
Payloads are separated by bullets ( · ), launches by pipes ( | ). Crewed flights are indicated in underline. Uncatalogued launch failures are listed in italics. Payloads deployed from other spacecraft are denoted in (brackets).