What is it about?
On 28 February 2025, AFRL flew the OSPREE payload on Varda’s W-2 hypersonic testbed and recorded in situ optical emission from the reentry shock layer, from 105 km down to 50 km (about Mach 29.5 to 15). This paper is the mission and data paper: reconstructed trajectory, the spectra, and how key molecular (CN, C2, CH) and atomic (O, O+, N, H) features evolve. Rotational and vibrational temperatures from spectral fits give a time history of shock-layer thermometry. Features also point to interaction between the flow and the vehicle’s thermal protection system.
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Why is it important?
Almost all reentry emission data are remote (airborne or ground). In situ spectra through the plasma sheath are scarce, and they are what nonequilibrium DSMC and CFD actually need for validation. This dataset is the benchmark behind the later W-2 modeling papers.
Perspectives
The measurements paper. If you want the flight story and the raw spectral evolution, this is the one. Modeling papers should cite this, not the other way around.
Zach Davis
Space Dynamics Laboratory
Read the Original
This page is a summary of: Return of OSPREE: In Situ Spectroscopic Measurements During Atmospheric Reentry, Journal of Spacecraft and Rockets, December 2025, American Institute of Aeronautics and Astronautics (AIAA),
DOI: 10.2514/1.a36508.
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