In this photograph, astronaut Eugene Trinh, a payload specialist for this mission, is working at the Drop Physics Module (DPM), and mission specialist Carl Meade is working on the experiment at the Glovebox inside the first United States Microgravity Laboratory (USML-1) Science Module. The USML-1 was one of NASA's missions dedicated to scientific investigations in a microgravity environment inside the Spacelab module. Investigations aboard the USML-1 included: materials science, fluid dynamics, biotechnology (crystal growth), and combustion science. The DPM is dedicated to the detailed study of the dynamics of fluid drops in microgravity. The Glovebox offers experimenters new capabilities and technologies in microgravity with a clean working space and minimizes contamination risks to both Spacelab and experiment samples. Payload specialists are professional scientists or engineers whose only assignment on a space flight is to carry out scientific and technological experiments. Their specific training for a space flight is usually limited to a short period of learning how to live and work in weightlessness. Mission Specialists are both professional scientists and career astronauts. Thus they are a link or bridge between the other crew members, and combine the functions of resident maintenance engineers, in-space counterparts of flight engineers in aircraft, and fully qualified scientists. The USML-1 flew aboard the STS-50 mission on June 1992, and was managed by the Marshall Space Flight Center.