The Solar One / Solar Two Experimental Facility is located near Daggett in California's Mojave desert. Solar One pilot project, (1982 to 1988), used an array of large mirrors, (heliostats), that tracked the sun and reflected solar energy onto a central tower. Heat transfer fluid was used to carry absorbed energy to a boiler and a steam turbine generator on the ground. Solar One was upgraded to Solar Two, (1995 to 1999), by adding more heliostats and using a different heat transfer fluid. The facility was converted into an Air Cherenkov Telescope, (ACT), in 2001 by the University of California.