NASA’s OSIRIS-APEX spacecraft completed a crucial flyby of Terra on September 23, 2025. The maneuver used our planet’s gravitational force to propel the probe on its new trajectory, which has the asteroid Apophis as its final destination. The encounter is scheduled to take place in April 2029, when the celestial body will make a historically close passage to Terra.
During the approach, which reached a minimum point of 3,438 kilometers above Oceano Atlântico, the probe’s instruments were activated. The mission team took the opportunity to capture images and collect data from the Terra-Moon system, performing an essential calibration of the sensors before the long journey through deep space.
This procedure marks a new phase for the spacecraft, previously known as OSIRIS-REx. Após the success of its primary mission, which consisted of collecting and returning samples from the asteroid Bennu in 2023, the probe was redirected towards this new and ambitious scientific objective.
Details of the gravity assist maneuver
The gravitational assist technique, also known as “gravity slingshot”, is fundamental for long-duration interplanetary missions. When passing close to a massive body like Terra, the probe “steals” a small amount of its orbital energy, resulting in a significant increase in its own speed in relation to Sol. In the case of OSIRIS-APEX, the speed was increased by approximately 5 km/s, a gain that would be impossible to achieve with just the fuel on board, making the mission viable from both a technical and financial point of view.
The main objective of the flyby was to adjust the spacecraft’s orbital plane, changing its inclination by around 18 degrees. Essa course correction is essential for the probe’s trajectory to perfectly align with the orbit of
Apophis: a target of high scientific interest
Asteroid 99942 Apophis is not just any target. With around 370 meters in diameter, this S-type rocky body is classified as an Asteroide Potencialmente Perigoso due to its orbit that crosses that of the Terra. Sua passage on April 13, 2029 will be extraordinarily close, just 32,000 kilometers from the surface, a distance shorter than that of some geostationary satellites. OSIRIS-APEX will arrive at the asteroid shortly after this encounter, with the main objective of studying how the gravitational force of Terra affected its internal structure, rotation and surface. Scientists seek to understand phenomena such as possible regolith landslides or “asteroid earthquakes”, providing unprecedented data on the dynamics of celestial bodies under the influence of planetary gravitational tides.
Visual records of the land flyover
The OCAMS camera suite was heavily used during the passage. MapCam, one of the cameras in the set, captured a stunning color composite showing the Australian continent.
This image was recorded approximately nine hours after the point of closest approach, when the probe was already approximately 228 thousand kilometers away from the planet.
Another instrument, the StowCam, produced a video made up of 424 individual frames. The sequence shows the Terra rotating as the ship flies over the Atlântico, with the América of the Sul visible in the left corner.
Additionally, a combined image of Terra and Lua was taken from a distance of 596,000 kilometers, offering a unique perspective on our planetary system.
Instrument calibration in mid-flight
The passage through Terra served as an ideal reference point for the calibration of scientific equipment. By pointing the sensors at an object with well-known characteristics, such as the atmosphere, oceans and Earth’s surface, the mission team was able to verify the accuracy and functioning of each instrument.
Next steps on the journey to 2029
With the ground maneuver completed, OSIRIS-APEX now enters a cruise phase that will last several years. The current trajectory will lead it to carry out other solar flybys to refine its path.
Arrival at asteroid Apophis is scheduled for April 2029. Upon entering orbit, the probe will begin a period of intensive study that will last 18 months.
During this period, the mission will map the surface in high resolution, analyze its chemical and mineralogical composition and investigate its internal structure to understand its cohesion.
The legacy of the OSIRIS-REx mission
The extended OSIRIS-APEX mission is only possible thanks to the extraordinary success of its original phase. Como OSIRIS-REx, the spacecraft traveled to the asteroid Bennu, where it made a daring landing to collect samples.
These samples were brought back to Terra in a capsule in September 2023, providing pristine material from early Sistema Solar for study in laboratories around the world.
Project management and collaboration
The project continues under the overall management of NASA’s Goddard Space Flight Center. Scientific leadership and data processing remain with Universidade of Arizona.
Company Lockheed Martin Space is responsible for the construction of the ship and flight operations. The mission also has the contribution of the laser altimeter (OLA), provided by Agência Espacial Canadense.
