On 4 July 2004, the scientific payload, Imager of Sprite for Upper Atmospheric Lighting (ISUAL), of FORMOSAT-2 satellite successfully observed the first images of sprites, sprite halo, and elves.

FORMOSAT-2 was launched from Vandenberg Air Force Base at California-USA on 21 May 2004, with two payloads onboard to perform remote sensing of Earth and to study upper atmospheric transient luminous phenomena above thunderstorms. On 6 June 2004, after FORMOSAT-2 was passed the basic functional tests and transferred to the mission orbit at 891km elevation, ISUAL was first switched on.

ISUAL payload consists of three sensors and one control unit. Within the sensors, there are four sets of high-voltage power supply module, up to 6300V, to energize the sophisticated ISUAL imager and spectrophotometers. Hence, the ISUAL high voltages have to be gradually raised with extremely careful. Images and spectrophotometric data can then be downlinked from the FORMOSAT-2 satellite and be examined thoroughly. Through the close collaboration of NSPO and ISUAL team members including Dr. Alfred Chen, Mr.Tian-Hsiung Huang, Mr. Cheng-Ling Kuo, Mr. Tze-De Wang (NCKU), Dr. Harald Frey (UC-Berkeley, USA), and Dr. Yukihiro Takahashi (Tohoku University, Japan), ISUAL has reached the commission status on 1 July 2004.

Since ISUAL is the first instrument dedicating to study transient luminous phenomena above thunderstorms from space, the strategy to capture these elusive flashes has to be formulated anew and re-adjusted often. After several nights of intensive search, ISUAL has successfully recorded the first images sprites and sprite halo on 4 July and elves on 5 July. The first sprite image was recorded on UT 14:40:24, 4 July 2004, over Mindanao-the Philippines. In the images, the big bright patch was due to the cloud-to-ground lightning. Immediate above the bright patch was a filamentary sprite and was topped by a pancake-shaped sprite halo. On UT 21:31:15, another sprite, dancing over the top of a thunderstorm over the Congo Basin, Africa, was recorded. On 5 July 2005, ISUAL recorded two more elves; the one occurred over Mindanao-the Philippines on UT 14:41:57 had a clear pancake shape which could be easily recognized. These initial successes have elevated the spirit of ISUAL team enormously.