NASA’s OSIRIS-REx spacecraft has embarked on an extended mission, newly renamed OSIRIS-APEX, to study the asteroid Apophis after successfully completing its primary mission of collecting samples from the asteroid Bennu.
OSIRIS Spacecraft Completes Primary Mission, Renamed for New Journey
The Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) spacecraft recently departed the near-Earth asteroid Bennu, carrying samples it collected from the asteroid’s surface in 2020.
After releasing the Sample Return Capsule that contains the samples collected from Bennu, OSIRIS-REx underwent a series of orbital maneuvers to propel itself away from the asteroid. It has now begun its extended mission, renamed OSIRIS-APophis EXtended (OSIRIS-APEX), during which it will study another asteroid called Apophis.
“OSIRIS-REx’s many accomplishments demonstrated the daring and innovate way in which exploration unfolds in real time,” said Thomas Zurbuchen, associate administrator for science at NASA Headquarters. “The team rose to the challenge, and now we have a spacecraft ready for further exploration.”
Targeting the ‘God of Chaos’ Asteroid
The target of OSIRIS-APEX’s extended mission is the 1,214-foot wide near-Earth asteroid named Apophis. Nicknamed the “God of Chaos,” Apophis will make a close approach by Earth in 2029, coming within 20,000 miles of our planet’s surface.
This will be the closet approach by such a sizable asteroid in over 100 years. Apophis orbits the Sun every 324 days, bringing it back around for another close pass of Earth in 2036, then again in 2068 due to the way its orbit aligns.
| Asteroid | Size (Feet) | Closest Earth Approach |
|---|---|---|
| Apophis | 1,214 | 2029, 2036, 2068 |
There is a small chance – around 1 in 150,000 – that Apophis could pass through a gravitational keyhole during its 2029 flyby which could set up an impact with Earth in future close approaches, in 2036 or even later in 2068. Scientists are eager to study Apophis further during OSIRIS-APEX’s mission to refine these odds.
Extended Mission Science Goals
By studying Apophis up close during OSIRIS-APEX, scientists hope to gain insight into the asteroid’s orbit and the possibility of an Earth impact. OSIRIS-APEX will spend over a year mapping and studying Apophis to analyze its size, shape, mass, gravity field, material composition, and orbital trajectory to help determine if and when it might impact Earth.
“The spacecraft is healthy and capable of operating into 2026,” said Ellen Howell, OSIRIS-REx project manager at NASA/Goddard. “This successful encounter opens up an entirely new phase of science and discovery as OSIRIS-REx fulfills its new role as a classified planetary defense asset.”
Key OSIRIS-APEX science goals include:
- Precisely determine Apophis’ orbit to better predict its future path and odds of impacting Earth
- Study surface geology and sample composition to understand origins and types of asteroids that could threaten Earth
- Test asteroid deflection technology to better prepare planetary defense stratergies
Extended Mission Trajectory and Timeline
After conducting a final flyby of Earth on December 27, 2023 to adjust course, OSIRIS-APEX will reach Apophis in mid-August 2026. It will maneuver into orbit around the asteroid to conduct detailed surveys over one Earth-year.
The spacecraft will first study Apophis from a distance of 20 miles, then move into closer circular orbits at 2 miles and just half a mile from the surface. Its instruments will map Apophis’ surface geology and composition in detail during this time to document variations across the asteroid.
In late 2027, OSIRIS-APEX may attempt to collect one or more surface samples before finally leaving orbit around Apophis in October 2028. The samples could provide direct evidence to confirm ground observations and would bring back the first materials from a potentially hazardous asteroid.
Importance for Planetary Defense
In recent years, NASA has expanded its planetary defense activities to better prepare for the possibility an asteroid could threaten Earth. While no known asteroid larger than 140 meters in diameter has a significant chance of impacting Earth over the next century, only about 40 percent of threatening asteroids of that size or larger have been found to date.
OSIRIS-APEX represents a unique opportunity to conduct an extended mission visiting a potentially hazardous asteroid. In addition to collecting vital scientific data, experience gained during this mission will aid in development of future capabilities to study other Earth-approaching asteroids. Information returned by OSIRIS-APEX could one day prove critical if Asteroid Apophis is ever determined to be on an Earth-impacting trajectory.
Next Steps
After completing operations at Apophis in late 2028, OSIRIS-APEX may be targeted to fly by yet another asteroid while it still has sufficient propellant. Otherwise, the spacecraft will be placed in a stable orbit around the Sun where it can continue transmitting asteroid tracking data.
Meanwhile, analysis of the Bennu samples returned to Earth in 2023 has only begun. As scientists study the material collected from humanity’s first asteroid sample return mission, OSIRIS-APEX turns to its new task – tracking the God of Chaos across the solar system on its upcoming close encounters with our planet.
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