NASA

NASA's InfrastructureWhen you think of NASA, most people think of the astronauts, but there's a lot more to the organization. To accomplish NASA's basic mission, they need people to develop and build new technologies, assemble and test spacecraft and their components, train astronauts/pilots and provide mission support services. With each task, there are workers to employ and pay, contractors to hire and supplies to purchase. NASA requires an enormous work force (over 18,000 employees and 40,000 contractors) and a large budget ($17.3 billion estimated for fiscal year 2008). NASA must have an infrastructure to deliver goods and services and account for the money spent.

Mission PlanningMission planning happens in 3 phases: Preflight, Flight and Extended Operations.
Preflight - Someone (scientists in NASA or external) proposes a mission to answer a scientific question. If NASA accepts the proposal, they assign a Scientific Working Group at a NASA Center to determine the mission goals, spacecraft designs, trajectories, launch vehicles and costs. If the project continues, NASA assigns scientists at various centers to build and test the spacecraft (usually with the help of contractors) and work on other aspects of the mission.
Flight - KSC launches the mission and hands it off to one of the NASA centers. The Deep Space Network receives data for the spacecraft in flight. When the spacecraft "encounters" its destination, scientific experiments are carried out and data transmitted to Earth. They send the information to various scientific teams that analyze the data and publish the findings.
Extended Operations - Spacecraft continues to send back data until it no longer works. In some cases, it may be possible to redirect it for a secondary objective. Human missions and some sample return missions come back to Earth