ISUAL, Imager of Sprites and Upper Atmospheric Lightning, is a set of scientific payload instruments onboard the FORMOSAT-2 satellite, which is the second satellite from Taiwan, and this mission kicked off since 1997 and launched on May 20, 2004. The main scientific goals of this mission are to investigate lightning induced, luminous atmospheric phenomena, including sprite, elve, halo, blue and gigantic jets, as well as polar aurora and upper atmospheric airglow. With the effort from an international team, including a lot of NCUIA alumnus, this mission has been operating for 15 years smoothly. The success of this mission greatly changed the understanding to the mysterious transient luminous events and atmospheric electricity. In this talk, the background and scientific objectives, transient luminous events, are introduced briefly. The ground observation including optical campaign and continuous recording at low frequency radio bands is greatly inspired by astronomical observation and will be focused on this talk. Finally, the major scientific results and their impacts of this mission will be presented.