Watching Apollo in action in its dedicated darkroom in the European Solar Test Installation (ESTI) in Ispra, Italy, puts a whole new sizzle on PV calibration: shutters slowly swing open revealing an array of 11 zenon lamps while several feet ahead a curtain draws aside. The air conditioning system provides the soundtrack, which is on at full blast to ensure temperature stability. The Apollo AAA large-area steady-state solar simulator (from Taiwan’s All Real Technology Company, the only one currently in use in Europe) is one of several new simulators at ESTI’s facilities, inaugurated this June following a €3 million refurbishment.