OSIRIS-APEX spacecraft takes selfie with Earth during flyby
On the left, this image shows SamCam, provided by the U of A to track the spacecraft’s sample head during its primary mission. The Y-shaped sample return capsule release mechanism is visible in the center in its deployed position. The OSIRIS-REx Laser Altimeter, provided by the Canadian Space Agency to create detailed 3D topographical maps of Bennu, is behind the release mechanism. To the right, one of the spacecraft's two navigation cameras, or NavCams, is visible.
NASA/Goddard/University of Arizona/Lockheed Martin
After successfully scooping up a sample from asteroid Bennu and sending it to Earth for study in 2023, NASA's OSIRIS-REx spacecraft became OSIRIS-APEX and was tasked with a new mission: study asteroid Apophis, another near-Earth asteroid that could pose a threat as a potential impactor of Earth far in the future.
On Sept. 23, the OSIRIS-APEX (Origins, Spectral Interpretation, Resource Identification, and Security – Apophis Explorer) spacecraft swung by Earth within 2,136 miles (3,438 kilometers) before heading into deep space for another trip around the sun. This so-called Earth gravity assist – the first of three such maneuvers planned for the remainder of the mission – is essential to ensure the spacecraft will rendezvous with Apophis in 2029.
About nine hours after its closest approach, OSIRIS-APEX took this image of Australia and the Pacific Ocean from about 142,000 miles away on Sept. 24. This color composite combines six images from the MapCam imager, which is part of the OSIRIS-REx Camera Suite, or OCAMS, operated by the University of Arizona.
NASA/Goddard/University of Arizona
During its approach and as it passed Earth, OSIRIS-APEX looked home using its suite of three cameras, built at the University of Arizona Lunar and Planetary Laboratory, to capture images and data of our planet to help calibrate its instruments.
The maneuver is not only critical for getting the spacecraft to its target but also ensures it will be ready for the research operations it is tasked with once it gets to Apophis, according to the mission's principal investigator, Dani Mendoza DellaGiustina, an assistant professor at LPL.
"This is not just about cool pictures, but about collecting data and important science milestones," she said. "Most importantly, the fly-by offered a rare opportunity for us to calibrate our instruments."
The robot geologist that is OSIRIS-APEX has been through a lot since its encounter with Bennu – from punching the asteroid to enduring cycles of heating and cooling each time the spacecraft swung around the sun and back into cooler regions of space.
"It is very important for the science team to understand how its history has affected the instruments since it was built and launched," DellaGiustina said. "When it touched down on Bennu, the spacecraft got pretty dusty, and some of that dust settled on instrument lenses. One of our most important tasks is to recalibrate our instruments and make sure they're ready to take measurements at Apophis."
An unexpected boon
Since the imaging suite on the OSIRIS-REx spacecraft was designed for its primary mission – studying asteroid Bennu, one of the darkest objects in the solar system – the fine layer of dust acquired during the sample acquisition provides an unexpected boon to its upcoming observation campaign at Apophis, DellaGiustina said.
OSIRIS-APEX was about 370,000 miles from Earth when it captured this view of the moon (on the far left) and Earth (on the far right) on Sept. 24, 2025. Sunlight reflects off the spacecraft’s instruments in the foreground.
NASA/Goddard/University of Arizona/Lockheed Martin
"Now we're going to an object that's about 10 times brighter," she said. "So the dust actually benefits us in some ways, in that it just sort of darkens everything a little bit. (With the data acquired during the flyby), we can quantify that effect and figure out how exactly we're going to adjust some of our instrument settings accordingly."
During its cruise period, between sample return and its rendezvous with Apophis, the spacecraft spends a total of six years transiting the inner solar system. Most of the time, it flies through empty space, far away from any celestial bodies. However, the spacecraft makes several close passes by Earth to steer it towards Apophis.
"We have done three Earth gravity slingshots, and we have two more to go," DellaGiustina said. "Each of those maneuvers is targeted to do something slightly different."
A slingshot is a rare opportunity to use an object – in this case, Earth and the moon – to fill the frame of the spacecraft's imaging instruments. In addition to a suite of cameras, these also include spectrometers – detectors designed not to record images, but to analyze light signatures that offer clues about the chemical and physical makeup of whatever they are pointed at. While the team can use stars to perform at least some degree of the necessary calibrations, spectral instruments require an object to fill the frame.
Watch the spacecraft pass by Earth on the NASA blog.
"We only have two more opportunities to get so close to an object before we arrive at Apophis – in this case, Earth – that it actually fills the fields of view of the spot spectrometers, so this most recent one is the chance that we have to understand if and how their behavior has changed," she said.
Other changes in the spacecraft's configuration result from the actions performed as part of its previous mission. During the spacecraft's primary mission, the StowCam instrument was used to verify that the sample material from asteroid Bennu was safely stowed in the sample return capsule for the journey back to Earth. No longer obstructed by the capsule, StowCam now provides a view of the instrument panel. StowCam also collected imagery as OSIRIS-APEX approached and departed from Earth.
Valuable opportunities
Earth flybys present valuable opportunities for the OSIRIS-APEX mission team, which consists both of OSIRIS-REx veterans and new members, to get up to speed performing operational and observational tasks and brush up on skills during an otherwise uneventful cruise phase, DellaGiustina explained.
"This is their opportunity to begin training in the processes and procedures that we will use to observe our target, and while it's not Apophis in this case, we're using a lot of the same software," she said. "We also have to build certain sequences to have the instruments acquire data, and we're working through all those processes. There is a lot of stuff we haven't done in quite a while.
"The bottom-line is we have a healthy, happy spacecraft," she added. "It survived the perihelion passages and everything indicates it's in great shape. We have incredible data coming in from the spacecraft, pulling off this set of observations was a lot of work done by a pretty small number of people, and so to see everything be such a success, is really satisfying."
NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering, and the safety and mission assurance for OSIRIS-APEX. The University of Arizona leads the science team and the mission's science observation planning and data processing. Lockheed Martin Space in Littleton, Colorado, built the spacecraft and provides flight operations. NASA Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-APEX spacecraft. International partnerships on this mission include the spacecraft's laser altimeter instrument from CSA. OSIRIS-APEX (previously named OSIRIS-REx) is the third mission in NASA's New Frontiers Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, for the agency's Science Mission Directorate in Washington.
