The OSIRIS-REx spacecraft will pursue a touch down onto the surface of the asteroid Bennu this August to collect samples of the asteroid to be brought back to Earth. This will be NASA's first attempt and is not an easy feat to complete. Microgravity from the asteroid's mass and the impact from grabbing a sample too close to the asteroid can cause a toll on the spacecraft.

For preparation, NASA will do a practice session of the landing this week and dubbed the drill the "Checkpoint" rehearsal. This will bring OSIRIS-REx the closest it has ever been to Bennu, at a distance of approximately 243 feet away from the asteroid.

Practice Makes Perfect: The "Checkpoint" Rehearsal

The touchdown event that will commence in the summer will involve three steps: orbit departure, Checkpoint maneuver, and finally, the Matchpoint maneuver that leads to the touchdown. This week's Checkpoint rehearsal will focus on the first two of these three maneuvers. NASA states that it is giving the team a chance to make sure that the spacecraft's Natural Feature Tracking system is in tip-top shape and that the other systems are working accordingly.

The rehearsal will take about four hours to complete and will also include the extending of the craft's robotic arm, the Touch-And-Go Sample Acquisition Mechanism. Practicing the spacecraft rotating into position would also be exercised as it is essential for the sampling event.

Experts found the selection of a definite landing site for OSIRIS-REx difficult as the asteroid's surface was found to be rugged. With the aid of the public, a suitable site had been selected in a gravel-strewn pit near the asteroid's north pole, known as Nightingale.

The OSIRIS-REx's solar clusters will enter a Y-wing configuration, and the spacecraft will lower to an altitude of 410 feet. After a successful rehearsal session, the spacecraft will be placed back into its original orbiting position around the asteroid Bennu.

Another practice rehearsal is prepared for June this year and will wrap up the Matchpoint burn and bring the spacecraft down to an altitude of 82 feet. The actual mission is set to happen on August 25, 2020.

101955 Bennu

101955 Bennu is an asteroid in the Apollo group discovered by the LINEAR Project on September 11, 1999. Named after Bennu, the ancient Egyptian mythological bird, the asteroid is deemed potentially hazardous and is listed on the Sentry Risk Table with the second-highest cumulative rating on the Palermo Technical Impact Hazard Scale. It has an increasing 1-in-2,700 chance of impacting Earth between 2175 and 2199.

Bennu was believed to have originated from a more massive carbon-rich asteroid, which had broken down about 700 million to 2 billion years ago. It likely formed in the Main Asteroid Belt between Mars and Jupiter, and has moved aimlessly closer to Earth since then.

The asteroid completes an orbit around the Sun every 1.2 years. It makes one full rotation on its axis every 4.3 hours. Every six years, it comes to close encounters with the Earth, although the exact distance from the two bodies varies each time. Its orbital path is tilted about 5 degrees relative to Earth's.

The asteroid has a mean diameter of 490 meters and has been observed extensively with the Arecibo Observatory planetary radar and the Goldstone Deep Space Network. Earlier this year in March, NASA's OSIRIS-REx team members were able to assign the first official names to Bennu's features to be approved by the International Astronomical Union.