OSIRIS-APEX To Approach Sun for Asteroid Apophis Encounter

NASA’s OSIRIS-APEX spacecraft, formerly known as OSIRIS-REx, is preparing for its first major test in its mission to asteroid Apophis. In order to reach the asteroid, the spacecraft will fly closer to the Sun than ever before, exposing its components to higher temperatures than they were originally designed for.

On January 2, 2024, at its closest approach (perihelion), OSIRIS-APEX will be approximately 46.5 million miles away from the Sun. This is about half the distance between Earth and the Sun, and well inside the orbit of Venus. However, it is 25 million miles closer to the Sun than the spacecraft was initially designed to operate, as the Apophis rendezvous was not part of the original mission plan.

After OSIRIS-REx successfully collected a sample from asteroid Bennu and delivered it to Earth in September 2023, the team proposed a bonus mission to Apophis. NASA agreed, and OSIRIS-APEX was born. To reach Apophis in April 2029, the spacecraft will undergo six close passes by the Sun and three Earth gravity assists.

To protect its critical components during these passes, engineers at Lockheed Martin Space developed a unique spacecraft configuration. The spacecraft will maintain a fixed orientation with respect to the Sun and reposition one of its solar arrays to shade its most sensitive components. Thermal models indicate that this configuration will keep the spacecraft safe.

“We’ve done a lot of modeling to ensure the spacecraft will be safe,”

said Dani Mendoza DellaGiustina, principal investigator for OSIRIS-APEX at the University of Arizona. However, taking a piece of space flight hardware beyond its design criteria always carries some risk.

This week, the spacecraft is executing commands to tuck in one of its two solar arrays while keeping the second extended for power production. During this time, the spacecraft will be inactive, with only critical systems turned on. Communication with Earth will be at low data rates, providing limited information about the spacecraft’s status. Once OSIRIS-APEX is farther from the Sun in March and April, engineers will turn on the instruments to test them.

Overall, the OSIRIS-APEX mission represents an exciting opportunity to explore and study asteroid Apophis in greater detail.