For scientists who spend a decade or more planning, designing, lobbying for, building, and testing exploratory spacecraft, the launch is always a pucker factor moment.

Years and years of work. Millions or even billions of dollars. It can all go up in a puff of smoke in seconds if something goes wrong with the rocket. Unlike with most human spacecraft, there are no emergency escape systems for scientific spacecraft. Some of these delicate payloads would be unlikely to survive the violent escape thruster firings, anyway.

“For most missions, launch contributes the majority of mission risk,” explained Thomas Zurbuchen, the associate administrator for science missions at NASA. “If the spacecraft is in space, most risk is behind us.”