OSIRIS-REx: Sampling an asteroid
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| Illustration of OSIRIS-REx "tagging" Bennu. Credit: NASA's Goddard Flight Center |
You can build your own model of OSIRIS-REx/APEX out of LEGO here.
NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) is NASA's asteroid sample return mission. The spacecraft is currently on its way back with the samples, planning to drop them off in September this year.
The Mission
OSIRIS-REx was launched on September 8, 2016 on an Atlas V rocket. OSIRIS-REx's target was the asteroid Bennu, a small Near Earth Object (NEO). NASA selected Bennu, then known as asteroid 1999 RQ36, due to its proximity to Earth, and small size. OSIRIS-REx approached Bennu on December 3, 2018. A few weeks later, on December 31, 2018, OSIRIS-REx entered orbit around Bennu.
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| Bennu full rotation. Credit: NASA's Goddard Flight Center/University of Arizona |
OSIRIS-REx spent the next year mapping Bennu's surface, and selecting possible landing sites. Bennu's surface was more rocky than anticipated, but a sampling site was selected nonetheless. OSIRIS-REx lowered to the surface and "tagged" a sample on October 20, 2020. The plan was to collect 60 grams from Bennu, but the sample arm managed to grab a whole 250 grams of material! The sample arm was so stuffed that it couldn't fit in the reentry capsule for return to Earth. Some of the samples were allowed to float out of the sample arm so it could fit into the reentry capsule.
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| OSIRIS-REx collecting a surface sample. Credit: NASA/Goddard/University of Arizona |
Bennu is a "rubble pile" asteroid. This means it's just a loose collection of rocks held together by mutual gravity. When OSIRIS-REx "tagged" Bennu's surface, it partially disintegrated it, before it collapsed in on itself to fill the hole. OSIRIS-REx is now almost home with its sample, which was dropped off on September 24 this year. The capsule landed flawlessly in the Utah desert. After the samples are removed from the capsule, NASA will revealed the first samples, and the initial data collected from them on October 11, 2023.
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| The OSIRIS-REx return capsule safely back on Earth. Credit: NASA |
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| Clean room technicians opening the capsule in a temporary clean room. Credit: NASA/Keegan Barber |
The APEX Mission
In April 2022, NASA announced that the OSIRIS-REx spacecraft will be reused after it returns its samples to Earth. In October, the spacecraft will be redirected to meet up with the asteroid Apophis in 2029. This mission will rename the spacecraft OSIRIS-APEX, which stands for OSIRIS-APophis-EXplorer.
Apophis is a hazardous NEO that was discovered in 2004. It was once predicted to have a high chance of colliding with Earth in 2029 or 2036. However, newer orbital measurements show that it won't have a high chance of colliding with Earth for at least another century. In March of 2021, Apophis made its closest flyby of Earth before the one in 2029.
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| Apophis during its 2021 flyby of Earth. Credit: NASA/JPL-Caltech and NSF/AUI/GBO |
After approaching Apophis, OSIRIS-APEX will put itself into orbit around the asteroid. OSIRIS-APEX is planned to use its thrusters to blast off surface material, and get a peak into the inner layers of the asteroid (OSIRIS-APEX will not return samples from Apophis, because it only had one sample reentry capsule).
The Targets
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| Mosaic of Bennu. Credit: NASA/Goddard/University of Arizona |
- Date Discovered: September 11, 1999
- Designation: 101955 Bennu (1999 RQ36)
- Class: Apollo [NEO]
- Radius: 241 Meters
- Rotational Period: 4.3 Hours
- Orbital Period: 436.65 Days (1.2 Years)
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| Credit: UH/IA |
- Date Discovered: June 19, 2004
- Designation: 99942 Apophis (2004 MN4)
- Class: Aten [NEO]
- Radius: 170 Meters
- Rotational Period: 30.56 Hours
- Orbital Period: 323.75 Days (0.89 Years) (Apophis' orbital period changes slightly with every flyby of Earth, so this is just the current orbital period)
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