NASA has approved the design of a new spacecraft for its ambitious mission to collect the first ever samples from an asteroid in 2018.
NASA's team that will conduct the mission has been given the go-ahead to begin building the spacecraft, flight instruments and ground system, and launch support facilities.
The announcement was made after a successful Mission Critical Design Review (CDR) for NASA's Origins Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx).
"This is the final step for a NASA mission to go from paper to product," said Gordon Johnston, OSIRIS-REx programme executive at NASA Headquarters, Washington.
"This confirms that the final design is ready to start the build-up towards launch," said Johnston.
OSIRIS-REx is scheduled to launch in 2016, rendezvous with the asteroid Bennu in 2018 and return a sample of it to Earth in 2023.
The spacecraft carries five instruments that will remotely evaluate the surface of Bennu.
After more than a year of asteroid reconnaissance, the spacecraft will collect samples of at least 60 grammes and return them to Earth for scientists to study, NASA said.
"Successfully passing mission CDR is a major accomplishment, but the hard part is still in front of us - building, integrating and testing the flight system in support of a tight planetary launch window," said Mike Donnelly, OSIRIS-REx project manager at NASA's Goddard Space Flight Centre in Greenbelt.
Key mission objectives focus on finding answers to basic questions about the composition of the very early solar system and the source of organic materials and water that made life possible on Earth.
The mission will also aid NASA's asteroid initiative and support the agency's efforts to understand the population of potentially hazardous near-Earth objects and characterise those suitable for future asteroid exploration missions.
In January, NASA invited people around the world to submit their names to be etched on a microchip aboard the spacecraft.