From proposal to launch

Who builds the robots

The Jet Propulsion Laboratory began on 31 October 1936, when Caltech graduate students and enthusiasts tested rocket motors in the Arroyo Seco, a dry riverbed in Pasadena. It first worked for the U.S. Army and joined the newly created NASA in 1958, the same year it launched Explorer 1, the first American satellite.

Explorer 1 did more than circle the Earth: its Geiger counter discovered the radiation belts around our planet, which made it the first spacecraft to do science. Caltech has managed JPL for NASA ever since 1958.

Seven phases, from idea to closeout

NASA divides the life of every project into phases. The first two belong to formulation, when the mission is still being defined; the rest belong to implementation, when it is built and flown:

• Pre-Phase A: concept studies.
• Phase A: concept and technology development.
• Phase B: preliminary design and technology completion.
• Phase C: final design and fabrication.
• Phase D: system assembly, integration and test, launch.
• Phase E: operations and sustainment.
• Phase F: closeout.

Between the phases sit key decision points. At each one, the responsible decision authority judges whether the project is ready to move on. A mission can be slowed, redesigned or stopped at these gates.

Why it takes so long

A planetary spacecraft cannot be repaired after launch, and the planets line up for an efficient journey only at certain times. That is why so much of a mission’s life is spent in design reviews and testing on the ground, and why the phase that most people see, the flight itself, comes only in Phase E.

The other guides on this site follow a mission through that flight: how it is navigated, how it lands on Mars and how it stays in touch with Earth.