NASA's mission OSIRIS-REx begins surveying an asteroid called Bennu

Feb. 24, 2018, 3:53 a.m. By: Kirti


The countdown had already begun for the OSIRIS-REx mission (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) by NASA that had its launch on 8 September 2016 aimed to visit, Bennu, that is an asteroid that orbits the Sun very close to Earth, and once there, it will pick up a sample and bring it back to Earth in 2023.

Talking of Bennu, the asteroid orbits the Sun in an orbit that is nearly the same as that of the Earth unlike typical asteroids, such as the ones that float around in the belt between Mars and Jupiter. In fact, it’s so close to us that in the year 2135 the 500-metre-wide rock’s orbit will bring it into the Moon’s orbit. The asteroid is also classified as a ‘potentially hazardous object’ because it just might smash into Earth in a time that is at least 300 years away.

Science goals and objectives of the mission:

  • Origins: Return and analyze a pristine carbon-rich asteroid sample.

  • Spectral Interpretation: For telescopic data of the entire asteroid population, provide ground truth or direct observations.

  • Resource Identification: Map the mineralogy and chemistry of a primitive asteroid that is carbon rich.

  • Security: Of a small asteroid, measuring the effect of sunlight on the orbit, known as the Yarkovsky effect: the slight push created when the asteroid absorbs sunlight and re-emits that energy as heat

  • Regolith Explorer: At the sampling site at scales down to the sub-centimetre, documentation of the regolith (layer of loose, outer material).


Trojan asteroids are trapped in stable gravity wells, which precede or follow a planet called Lagrange points. OSIRIS-REx is currently travelling through Earth's fourth Lagrange point and is In the hope of identifying Earth-Trojan asteroids in the region the mission team will make the use of this opportunity in order to take multiple images of the area with the spacecraft’s MapCam camera.

“Because the Earth’s fourth Lagrange point is relatively stable, it is possible that remnants of the material that built Earth are trapped within it,” said Dante Lauretta. “So this search gives us a unique opportunity to explore the primordial building blocks of Earth.”

For the time period that the search took place, on each observation day, the spacecraft’s MapCam camera took 135 survey images that were to be processed and examined at the University of Arizona, Tucson by the imaging scientists of the mission.

This Mission: Surveying Begins this Year

Whether or not the team discovers any new asteroids, the search still proves to be a beneficial exercise. When the spacecraft approaches its target this year, the operations involved in searching for Earth-Trojan asteroids will anyhow closely resemble those that will be required to search for natural satellites and other potential hazards around Bennu. Being able to practice these mission-critical operations in advance will help the OSIRIS-REx team to reduce mission risk once the spacecraft arrives at Bennu.

In August 2018, an approach of OSIRIS-REx to Bennu will begin. In order to match the velocity of Bennu and rendezvous with the asteroid, it will use an array of small rocket thrusters. The spacecraft will begin a detailed survey of Bennu two months after slowing to encounter Bennu. As a part of the process that will last over a year, OSIRIS-REx will map potential sample sites.

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.

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.

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. Also, NASA aims to preserve at Johnson Space Flight Center in Houston at least 75% of the sample for further research by scientists as well as the future generations worldwide.

For More Information: NASA's mission OSIRIS-REx