Absolute Radiation Measurement in Venus and Mars Entry Conditions

Comparisons of experimental characterization and model predictions of entry radiation relevant to Mars and Venus exploration are presented. Characterization is performed in the recently upgraded Ames Electric Arc Shock Tube (EAST) facility. Tests are performed in Mars (96% CO2, 4% N2) and Venus (96.5% CO2, 3.5% N2) simulant gases at downstream pressures and incident velocities spanning from 0.1-2.0 Torr and 3-12 km/s. Velocity and pressure conditions were chosen based on expected flight conditions (direct entry or aerocapture) in Mars and Venus atmospheres. The absolute radiance data are spatially and spectrally resolved and span the vacuum ultraviolet (VUV) through mid-IR (120-1650 nm, 35 µm). Resolved spectra of the CO 4 th positive band in the VUV are reported for the first time. Measurements of CO2 molecular vibrational radiation is also attempted at low velocity conditions. Radiation modeled under equilibrium assumption with NEQAIR code compares favorably to measured radiation under some, but not all, conditions.