.

The staff of NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) gathered on the ramp outside the Dryden Aircraft Operations Facility in Palmdale, Calif., to mark a milestone—the flying observatory's 100th flight. The airborne observatory departed from the facility that evening on an engineering flight for the German Receiver for Astronomy at Terahertz Frequencies (GREAT) spectroscopic receiver. GREAT works like a very high frequency radio receiver that detects light waves rather than light particles. The GREAT instrument was developed by a consortium of German research institutes led by the Max Planck Institute for Radio Astronomy in Bonn, Germany. (NASA/Tom Tschida)