It was done after a successful Mission Critical Design Review by an independent review board, comprised of experts from NASA and several external organizations, Xinhua quoted NASA as saying.
"This is the final step for a NASA mission to go from paper to product," OSIRIS-REx programme executive Gordon Johnston said in a NASA statement. "This confirms that the final design is ready to start the build-up towards launch."
OSIRIS-REx is scheduled to launch in the fall of 2016, rendezvous with the asteroid Bennu in 2018.
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 2 ounces (60 grams) and return them to Earth for scientific study in 2023.
The mission is aimed at 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.
Besides, the mission will help achieve US President Barack Obama's goal of sending humans to an asteroid by 2025, NASA added.