Directional Scientific Objectives of the Interstellar Express Mission

In this paper, the main scientific objectives, observational requirements, and expected scientific returns of boundary exploration missions in different directions, such as the heliospheric nose and tail, were briefly introduced; the current research status at home and abroad was reviewed, including ongoing and proposed missions and their scientific payload configurations; several major scientific questions related to heliospheric physics, the interstellar medium, and solar system evolution in different directions were summarized. Finally prospects for China’s future scientific development in independent boundary exploration were presented.