On Tuesday, NASA’s OSIRIS-REx performed the crucial goal of its mission around asteroid Bennu. It flew down to the surface of the space rock, briefly touched the soil, and grabbed a sample to eventually bring back home to Earth.
The team is still analyzing the data to confirm that the sample collection went as expected; in particular, to know if the spacecraft was able to snatch enough soil. While we wait for those results, some incredible images and videos have been released. This is our first look at the Touch-And-Go (TAG) event.
A TAG event has several challenges and OSIRIS-REx was designed and programmed to navigate them autonomously. Luckily, it appears that the team gave the spacecraft all the right tools to make the first-ever US attempt to sample an asteroid a success. The TAG Sample Acquisition Mechanism (TAGSAM), the articulated arm used by OSIRIS-REx to collect the material, touched the soil of the asteroid within 1 meter (3 feet) of the target location.
The spacecraft moved at a speed of about 10 centimeters (3.9 inches) per second down to the ground of the asteroid. It appeared to crush some porous rocks as it gently entered the regolith, its soil. One second after touchdown, it released nitrogen at high-pressure, lifting the soil up to be captured. The TAGSAM was in contact with the regolith for about 6 seconds, although most of the collection happened within the first 3 seconds.
Afterward, OSIRIS-REx moved to a safe distance, where it delivered data and these images, reassuring the mission team that all was well.
The next set of challenges is now underway. The goal of the TAG was to collect at least 60 grams (2.1 ounces) of regolith, although if we've been lucky TAGSAM can carry up to 2 kilograms (4.5 pounds). But how do you weigh things in space?
Taking on board mass in the form of sample material will change the spacecraft's spin.
“There’s a technique that we call the sample mass measurement where the spacecraft will re-extend the arm in a certain position and actually spin around. We look for a change in the moment of inertia. It has done this prior to TAG, so we know what the moment of inertia of the spacecraft is prior to TAG,” Beau Bierhaus, TAGSAM scientist at Lockheed Martin, told IFLScience.
The spacecraft will be soon pirouetting again, and the difference in this moment of inertia before and after TAG will tell the team how much mass it has collected.
If TAGSAM has enough regolith inside, the next big adventure is the return home. OSIRIS-REx will leave Bennu next year and, all going well, the capsule with its precious cargo will land in Utah in September 2023. Then it will officially become the third spacecraft ever, following the two Japanese Hayabusa missions, to return an asteroid sample to Earth.