Context: Recently, NASA’s OSIRIS-REx spacecraft has been orbiting asteroid Bennu for over a year now, since it arrived at the space rock in December 2018. Now, the spacecraft has successfully completed its ‘Checkpoint’ rehearsal and is one step closer to land on the asteroid’s Surface.
Key Points

• The rehearsal allowed the OSIRIS-REx team to test whether the various systems aboard the spacecraft like imaging, navigation and ranging systems worked as they should during descent.
• While landing the OSIRIS-REx autonomously checks its position and velocity at a location known as the checkpoint. At this position, it adjusts the trajectory down towards the surface.
• It was able to successfully deploy its sampling arm which is known as the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) and used the instruments on board to make observations of the sample site.
• Through the rehearsal, the team also confirmed that OSIRIS-REx’s Natural Feature Tracking (NFT) guidance system worked accurately.

About OSIRIS-REx Mission

• It stands for (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) is a NASA asteroid study and sample-return mission.
• The mission’s primary goal is to obtain a sample of at least 60 grams (2.1 oz) from 101955
• Bennu, a carbonaceous near-Earth asteroid, and return the sample to Earth for a detailed analysis.
• The material returned is expected to enable scientists to learn more about the formation and evolution of the Solar System, its initial stages of planet formation, and the source of organic compounds that led to the formation of life on Earth.
• If successful, OSIRIS-REx will be the first U.S. spacecraft to return samples from an Asteroid.

Its Objective

• Return and analyze a sample of pristine carbonaceous asteroid regolith in an amount sufficient to study the nature, history, and distribution of its constituent minerals and organic compounds.
• Map the global properties, chemistry, and mineralogy of a primitive carbonaceous asteroid to characterize its geologic and dynamic history and provide context for the returned samples.
• Document the texture, morphology, geochemistry, and spectral properties of the regolith at the sampling site in situ at scales down to millimeters.
• Measure the Yarkovsky effect (a thermal force on the object) on a potentially hazardous asteroid and constrain the asteroid properties that contribute to this effect.
• Characterize the integrated Global Properties of a primitive carbonaceous asteroid to allow for direct comparison with ground-based telescopic data of the entire asteroid population.

About Bennu asteroid

• Bennuis a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on September 11, 1999.
• It is a potentially hazardous object.
• It has a cumulative 1-in-2,700 chance of impacting Earth between 2175–2199.
• There is a well-defined ridge along the equator of asteroid Bennu.
• The presence of this ridge suggests that fine-grained regolith particles have accumulated in this area, possibly because of its low gravity and fast rotation.