Concluding a cosmic chemical census

One and a half million kilometres away from planet Earth, a bustling space observatory is slowly dying. It's running out of liquid helium. Without it, instruments will start to overheat and fail, the observatory will be unable to function and it will be left, floating impotently in space. When will the lights blink out? We're not exactly sure; Herschel probably has a few more months, but as the carrier of the largest, most powerful telescope ever flown in space, and with a mission no less fundamental than revealing how our galaxy came into being, Herschel's legacy will last far beyond the day the final data package is despatched to Earth.