OSIRIS-APEX on Track for Asteroid Apophis 2029 Encounter
The repurposed OSIRIS-REx spacecraft is bound for a historic rendezvous with asteroid Apophis, promising unprecedented observations of a near-Earth asteroid.
After successfully returning Bennu samples to Earth, the OSIRIS-REx spacecraft has been given a new lease on life. Now designated OSIRIS-APEX (Origins, Spectroscopy, Interpretation, Resource Identification, Security–Apophis Explorer), the spacecraft is en route to asteroid Apophis for a historic close encounter in April 2029.
"This is an extraordinary opportunity," says Dr. Michael Nolan, the OSIRIS-APEX mission manager. "Apophis will make the closest approach of any known asteroid larger than 300 meters in at least the next 300 years. We will be there to observe it in unprecedented detail."
Why Apophis?
Asteroid Apophis presents a unique scientific and operational opportunity:
- • Close approach: Apophis will pass within 31,000 km of Earth—closer than geosynchronous satellites. This is the closest approach of a large asteroid in our lifetime.
- • Visible to the naked eye: Apophis will be bright enough to see without a telescope, a rare occurrence for an asteroid.
- • Planetary defense significance: Apophis is a near-Earth asteroid with measurable impact risk. Studying it informs planetary defense strategies.
- • Scientific diversity: Like Bennu, Apophis has much to teach us about asteroid properties and composition.
The Mission Timeline
OSIRIS-APEX is already on its way. The spacecraft left Bennu's orbit in May 2021 and has been traveling toward Apophis ever since. In April 2029, the spacecraft will be perfectly positioned to observe Apophis during its close approach to Earth, conducting detailed imaging, spectroscopy, and other observations.
Unlike the OSIRIS-REx phase at Bennu, OSIRIS-APEX will not attempt to land or collect samples. Instead, it will conduct remote sensing observations from a safe distance as Apophis passes near Earth.
What Will We Learn?
OSIRIS-APEX will gather crucial data about Apophis:
- → Surface composition: What minerals and materials make up Apophis?
- → Shape and rotation: How does Apophis rotate, and how will Earth's gravity affect it?
- → Structural properties: Is Apophis a rubble pile like Bennu, or a more coherent body?
- → Yarkovsky effect: How does solar radiation affect Apophis's orbit?
- → Impact implications: If Apophis were to threaten Earth, how would we deflect it?
A Watershed Moment for Planetary Defense
The OSIRIS-APEX mission serves a dual purpose: advancing scientific knowledge and demonstrating planetary defense capabilities. In 2022, NASA's DART mission successfully impacted asteroid Dimorphos, proving we can alter an asteroid's orbit. OSIRIS-APEX will provide a detailed view of another potentially hazardous asteroid, refining our understanding of what would be needed to deflect it if necessary.
"This is humanity showing we can reach out and study the objects that share our cosmic neighborhood," Dr. Nolan adds. "We're not passive observers—we're active participants in understanding and, if necessary, protecting ourselves from asteroid impacts."
The Broader Vision
OSIRIS-APEX represents the future of space exploration: reusable, repurposable spacecraft undertaking multiple scientific missions across the solar system. The same spacecraft that brought Bennu's secrets home is now racing toward Apophis. Future spacecraft may undertake similar extended missions, visiting multiple asteroids, moons, and planets in a single journey.