As sun sets, a Falcon 9 rocket stands ready for liftoff at the Kennedy Space Center's Launch Complex 39A. The historic launch site now is operated by SpaceX under a property agreement signed with NASA. In the background is the Vehicle Assembly Building. The rocket will boost a Dragon resupply spacecraft to the International Space Station. Liftoff is scheduled for 10:01 a.m. EST on Feb. 18. On its 10th commercial resupply services mission to the space station, Dragon will bring up 5,000 pounds of supplies, such as the Stratospheric Aerosol and Gas Experiment (SAGE) III instrument to further study ozone in the atmosphere. Once mounted on the space station, SAGE III will measure the Earth’s sunscreen, or ozone, along with other gases and aerosols, or tiny particles in the atmosphere.