Space Telescope Imaging Spectrograph. An instrument that acts like a prism to separate light from the cosmos into its component colors, providing a wavelength 'fingerprint' of the object being observed. The information yields clues about an object's temperature, chemical composition, density, and motion. Spectrographic observations also reveal changes in celestial objects as the universe evolves. Astronauts installed STIS aboard the Hubble Space Telescope in February 1997 during the Second Servicing Mission. STIS spans ultraviolet, visible, and near-infrared wavelengths. The spectrograph can sample 500 points along a celestial object simultaneously.