In September 2016, OSIRIS-REx will launch towards the near-Earth asteroid Bennu, which orbits between 1.356 and 0.897 astronomical units (AU) from the Sun (one AU is the distance from Earth to the Sun). It will arrive in 2018 and study the asteroid before it collects a sample between 60 grams and two kilograms (2.1 ounces and 4.4 pounds) in weight, the biggest ever for a robotic mission. In 2023, this sample will be returned to Earth – the largest returned sample since the Apollo missions – possibly revealing secrets of the early Solar System. It is the first U.S. mission to sample an asteroid.
And a crucial step has now been made towards its launch next year, with the delivery of a camera instrument suite to Lockheed Martin Space Systems in Denver, Colorado, to be installed on the spacecraft.
“This is another major step in preparing for our mission,” said Mike Donnelly, OSIRIS-REx project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in a statement. “With the delivery of the camera suite to the spacecraft contractor, we will have our full complement of cameras and spectrometers.”
In total, three cameras have been delivered, which will be responsible for imaging Bennu from a distance of two million kilometers (1.2 million miles) and also providing high-resolution imagery of the surface, so that a sample site can be picked.
The mission is certainly one to pay close attention to. Asteroid 101955 Bennu, to give it its full name, is about 500 meters (1,600 feet) wide. It is thought to be a remnant of the early Solar System, so studying it could reveal the origins of Earth and the other planets, and maybe even life itself. Bennu also has a very, very small chance (less than 0.07%) of hitting Earth in the late 22nd century, with eight potential impacts identified, so studying it in further detail will reveal its exact future trajectory.
Returning a sample from an asteroid has been on the agenda for some time; this mission itself was proposed and fought for by the late NASA planetary scientist Michael Drake. The mission is not unprecedented; both Japan’s Hayabusa and NASA’s Stardust have returned samples before, from an asteroid and comet respectively. However, both of those samples were minuscule, less than a gram in total. OSIRIS-REx’s will be much bigger.
To gather the sample, OSIRIS-REx will approach the surface and hover just meters away. It will then deploy a robotic arm called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM), which will contact the surface of Bennu for five seconds, releasing a burst of nitrogen gas. This will cause loose rocks and surface soil to be stirred up into a collector in the head of the arm. There will be enough nitrogen for three such attempts.
The head of the TAGSAM will then be placed in a sample return capsule back on the spacecraft for the journey home around March 2021. About two years later in September 2023, it will separate from OSIRIS-REx and re-enter Earth’s atmosphere, with a parachute slowing it down to land in the Utah desert. Once recovered, the science can begin.
If it sounds complicated, that’s because it is. Bringing a sample of this size back on a robotic mission is no mean feat. But with launch just a year away, we can start to get excited about what will be one of the most impressive space missions so far this millennia.
Image in text: The University of Arizona camera suite for OSIRIS-REx. University of Arizona/Symeon Platts.