Developing the OSPREE Payload for Spectroscopic Measurements of a Mach 25+ Plasma Sheath

Sensing atomic and molecular emissions from the radiant plasma sheath that forms around reentry spacecraft will advance the understanding and modeling of high-enthalpy flows. Optical emission spectroscopy (OES) measurements in this extreme environment can yield data needed to anchor aerothermal flow models in the Mach 20+ regime. This paper presents the development of an OES payload for a commercial reentry capsule, composed of commercial-off-the-shelf hardware modified for spaceflight. The flight-qualified sensor will yield novel optical emission spectra of the reentry plasma sheath from 350 to 800 nm, providing invaluable data characterizing the dynamic aerothermal chemistry of this unique environment. We present an overview of the sensor payload design and planned reentry experiment. The simulation of the sensor response in key flight regimes is presented from direct simulation Monte Carlo and computational fluid dynamics output coupled to the NEQAIR radiative emission tool, allowing for preflight understanding of the dynamic emissions of N2, N+2, O2, O+2, N, N+, O, O+, NO, and NO+ species that manifest in the plasma sheath.