OSIRIS-REx will launch from Cape Canaveral, Florida, on an Atlas V 411 rocket during a 34-day launch period starting Sept. 8, 2016. OSIRIS-REx will orbit the sun for a year, then use Earth’s gravitational field to assist it on its way to Bennu. In August 2018, OSIRIS-REx’s approach to Bennu will begin. It will use an array of small rocket thrusters to match the velocity of Bennu and rendezvous with the asteroid.
The spacecraft will begin a detailed survey of Bennu two months after slowing to encounter Bennu. The process will last over a year, and, as part of it, OSIRIS-REx will map potential sample sites. After the selection of the final site, the spacecraft will briefly touch the surface of Bennu to retrieve a sample. The sampling arm will make contact with the surface of Bennu for about five seconds, during which it will release a burst of nitrogen gas. The procedure will cause rocks and surface material to be stirred up and captured in the sampler head. The spacecraft has enough nitrogen to allow three sampling attempts, to collect between 60 and 2000 grams (2–70 ounces).
In March 2021, the window for departure from the asteroid will open, and OSIRIS-REx will begin its return journey to Earth, arriving two and a half years later in September 2023. The sample return capsule will separate from the spacecraft and enter the Earth’s atmosphere. The capsule containing the sample will be collected at the Utah Test and Training Range. For two years after the sample return (from late 2023-2025) the science team will catalog the sample and conduct the analysis needed to meet the mission science goals. NASA will preserve at least 75% of the sample at NASA’s Johnson Space Flight Center in Houston for further research by scientists worldwide, including future generations of scientists.