Europa Clipper’s ultraviolet spectrograph, called Europa-UVS, is the first of the mission’s science instruments to be installed on the spacecraft’s nadir deck, seen here in a clean room at NASA's Jet Propulsion Laboratory in Southern California. The nadir deck (the thick matte-gray polygonal structure filling about one-third of the image) will stabilize science instruments and other sensors to help ensure they are oriented correctly. The spectrograph is the gray and silver metal box on the upper right of the nadir deck, and one of the spacecraft’s star tracker telescopes is visible jutting from the nadir deck diagonally toward the upper right.