The Australian-German Contributions to the OSIRIS-REx Re-Entry Capsule Observation

A team of international scientists from Australia, Germany and the US partnered with NASA SCIFLI to undertake observations of the re-entry of the OSIRIS-REx sample return capsule. The team was split across two aircraft, one run by UniSQ-RTI and one by NASA SCIFLI, and three ground stations. The observation was undertaken on the 24th of September 2023 with nearly all locations measuring valuable data of the re-entry. Utilising the data collected by the team, and further data shared by NASA SCIFLI, the capsule re-entry trajectory was reconstructed and compared with predictions. The measured trajectory showed that the capsule entered at nearly 300 m/s faster than predicted. Subsequent atmospheric measurements showed that the upper atmosphere had a particularly low density at the time of re-entry, and a recomputed trajectory using the lower density matched the measurements very well. A range of spectroscopic measurements were also taken. Successful measurements of the oxygen 777 nm line were compared between instruments on the UniSQ-RTI and NASA522 aircraft. A difference in irradiance was measured between the aircraft and stations and cannot yet be explained. Further investigations into the discrepancy are ongoing.