A history-making NASA spacecraft has just received a new lease on life. OSIRIS-REx, which is currently on its way back to Earth with rock samples from asteroid Bennu, will now have its mission extended to visit another asteroid, Apophis.
After arriving at Bennu in December 2018, OSIRIS-REx spent more than two years in a close rendezvous with the asteroid, studying it before eventually swooping in and stirring up surface materials to collect samples of dust and rock. In May 2021 it began its 2.5-year journey back to Earth, to drop off these samples for close study by scientists.
In September 2023 as it approaches Earth, the spacecraft will jettison the sample return capsule, which will then enter the atmosphere and (hopefully safely) parachute down to the Utah Test and Training Range for collection. The original plan was for OSIRIS-REx itself to then fly off into a graveyard orbit of the Sun, somewhere between Mercury and Venus.
But now, NASA and the University of Arizona have announced a mission extension. OSIRIS-REx apparently still has plenty of fuel left in the tank, so the new plan is that after it drops off its payload it will head off to rendezvous with another asteroid – Apophis. The new phase will be known as OSIRIS-Apophis Explorer, or OSIRIS-APEX.
"Apophis is one of the most infamous asteroids," said Dani DellaGiustina, soon to be principal investigator of OSIRIS-APEX. "When it was first discovered in 2004, there was concern that it would impact the Earth in 2029 during its close approach. That risk was retired after subsequent observations, but it will be the closest an asteroid of this size has gotten in the 50 or so years asteroids have been closely tracked, or for the next 100 years of asteroids we have discovered so far. It gets within one-tenth the distance between the Earth and Moon during the 2029 encounter.”
The spacecraft will make its first maneuver towards Apophis 30 days after the sample drop-off. Once it arrives at its new destination, OSIRIS-APEX will perform the same kind of long-term rendezvous as it did with Bennu, staying with and studying the rock for 18 months.
It will even swoop down close to the surface and fire its thrusters to kick up dust, much like it did during the sample collection at Bennu. However, this time no samples will be taken – instead, the maneuver is designed to expose the subsurface material, to allow scientists to learn more about the asteroid’s composition and other properties.
The team also plans to study what effects Earth’s gravitational pull might have on the asteroid as it passes. For instance, it’s been hypothesized that Apophis might experience landslides as the planet’s gravity tugs on loose material.
Source: University of Arizona
