NASA’s OSIRIS-Apex will fly close to the Sun during its visit to asteroid Apophis.

NASA's OSIRIS-Apex will fly close to the Sun during its visit to asteroid Apophis.
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NASA's OSIRIS-Apex will fly close to the Sun during its visit to asteroid Apophis.

Undergoing a transformation into NASA’s OSIRIS-APEX, the spacecraft formerly identified as OSIRIS-REx is gearing up for a pivotal trial in its mission to asteroid Apophis. Aiming to delve closer to the Sun than ever before, the spacecraft is on the brink of exposing its components to heightened temperatures exceeding their initial design parameters.

During its imminent perihelion on January 2, 2024, OSIRIS-APEX will venture within approximately 46.5 million miles of the Sun—nearly half the distance between Earth and the Sun, and notably within the orbit of Venus. This proximity, however, marks a deviation of 25 million miles closer to the Sun than the spacecraft’s original operational design, a consequence of its unplanned detour from the original mission to asteroid Bennu.

Following its triumphant departure from Bennu in May 2021 with a precious sample on board, OSIRIS-REx exhibited vitality with a quarter of its fuel reserves and well-maintained instruments. Instead of retiring the spacecraft after delivering the Bennu sample to Earth on September 24, 2023, with the intention of sending it into a perpetual solar orbit, the team proposed an ambitious extension—directing it towards a bonus mission to rendezvous with Apophis. Embracing this proposal, NASA birthed OSIRIS-APEX (Origins, Spectral Interpretation, Resource Identification, and Security – Apophis Explorer).

The impending perihelion represents the initial step in a series of six close solar passes, coupled with three Earth gravity assists, that OSIRIS-APEX will embark upon to ultimately reach Apophis in April 2029. In preparation for these critical maneuvers, engineers at mission partner Lockheed Martin Space ingeniously configured the spacecraft to safeguard its essential components during this ambitious celestial journey.

Sandy Freund, OSIRIS-APEX program manager at Lockheed Martin Space in Littleton, Colorado, emphasizes the peak of creativity during the spacecraft’s flight when pushing boundaries to meet mission demands—an experience echoed from her role on OSIRIS-REx.In the pursuit of preventing overheating, the spacecraft adopts a fixed orientation relative to the Sun, strategically adjusting one of its solar arrays to shield sensitive components. Thorough thermal modeling supports the confidence that this configuration will ensure the spacecraft’s safety.

Dani Mendoza DellaGiustina, principal investigator for OSIRIS-APEX at the University of Arizona, Tucson, underscores the extensive modeling efforts to guarantee spacecraft safety. However, DellaGiustina acknowledges the inherent risks when venturing beyond design criteria, emphasizing the balance between innovation and risk mitigation. Notably, he serves as the deputy principal investigator of OSIRIS-REx as well.

In the current phase, the spacecraft is undergoing maneuvers this week to reposition one of its two solar arrays, keeping the second extended for power generation. Throughout this period, the spacecraft will enter an inactive state, activating only essential systems, including telemetry, and communicating with Earth at low data rates. Consequently, the mission team will receive limited information about the spacecraft’s status. As OSIRIS-APEX moves farther from the Sun in March and April, engineers plan to activate and test the instruments.

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