This review describes the on-orbit results and the lessons-learned of the small scientific satellite“INDEX”(Reimei) for aurora observations and demonstrations of advanced satellite technologies. INDEX is a small satellite with 72 kgmass, and is provided with three-axis attitude control capabilities for aurora observations. INDEX was launched into a nearlysun synchronous orbit on Aug. 23rd, 2005 (UT) from Baikonur, Kazakhstan by Dnepr rocket. The INDEX satellite has beenworking satisfactorily on orbit for 29 months as of January, 2008. Three axis control is achieved with an accuracy of 0.05 deg(la). INDEX indicates that even a small satellite launched as a piggy-back can successfully perform unique scientific missions.Reimei brings a dawn of advanced small satellites. This review concludes the perspective views for small satellites.