Earlier this year, the Far Infrared and submillimetre Space Observatory celibrated its 1001 Operational Day. I will take that opportunity to present a fantastic story, based on massive Swedish involvement already from the very beginning. Among many things, Sweden has contributed to the Heterodyne Instrument for the Far Infrared (HIFI). With the extraordinary sensitivity of HIFI and its very high resolving power, one of the outstanding issues has come to a closure. However, this opened new and unexpected challenges.
