TESS will be launched into orbit from the Kennedy Space Center perched atop a SpaceX Falcon 9 rocket in a mission costing $337m (£240m).
“One of the biggest questions in exoplanet exploration is: If an astronomer finds a planet in a star’s habitable zone, will it be interesting from a biologist’s point of view?” said George Ricker, TESS principal investigator at the Massachusetts Institute of Technology (MIT), which is leading the mission.
“We expect TESS will discover a number of planets whose atmospheric compositions, which hold potential clues to the presence of life, could be precisely measured by future observers.”
The latest Nasa astrophysics endeavour is designed to build on the work of its predecessor, the Kepler space telescope.
Nasa expects TESS to detect thousands more previously unknown worlds, perhaps hundreds of them Earth-sized or “super-Earth”-sized – no larger than twice as big as our home planet.
Such worlds are believed to stand the greatest chance of having rocky surfaces or oceans, and are thus considered the most promising candidates for the evolution of life, as opposed to gas giants similar to Jupiter or Neptune.
The spacecraft will be looking for a phenomenon known as a transit, where a planet passes in front of its star, causing a periodic and regular dip in the star’s brightness.
Nasa’s Kepler spacecraft used the same method to spot more than 2,600 confirmed exoplanets, most of them orbiting faint stars 300 to 3,000 light-years away.
But unlike Kepler, which fixed its glare on stars within a tiny fraction of the sky, TESS will scan the majority of the heavens for shorter periods and focus much of its attention on stars called red dwarfs, which are smaller, cooler and longer-lived than our Sun.
Astronomers hope to end up with anywhere from 10 to 30 more rocky exoplanets for further study.
The new probe will take about 60 days to attain its highly elliptical, first-of-a-kind orbit that will loop TESS between Earth and the Moon every two and a half weeks.
Kepler’s positioning system broke down in 2013, about four years after its launch, and it has nearly run out of fuel.
“So it’s perfect timing that we’ll be launching TESS to continue the great activity of looking for planets around stars other than our Sun and thinking about what it might mean for life in the universe,” Paul Hertz, Nasa’s director of astrophysics, told reporters at a news briefing in Washington on Wednesday.
TESS, roughly the size of a refrigerator with solar-panel wings, is equipped with four special cameras to survey 200,000 stars that are relatively near the Sun and thus among the brightest in the sky, seeking out those with planets of their own.