In order to estimate the emission intensity around a Mars Entry Capsule, an expansion tube is developed by updated the Hyper Velocity Shock Tube, which has been used for the radiation measurement from VUV to NIR wavelength region behind strong shock wave in Mars simulant gas. By expanded the low pressure tube inside the vacuum chamber, an expansion tube, which is called as Hyper Velocity Expansion Tube, is achieved. The test section, where test models are set, is located at the outlet of the expansion section. The test time and characteristics of the test flow are estimated theoretically and experimentally with air and CO 2 . The flow velocity can be around 6 km/s, which agree with a Mars entry condition. The radiation intensities in air and CO 2 are measured. The shock stand-off distances are mm in air and in CO 2 , respectively.
I. Introductionecently, several missions with the entry into the Martian atmosphere have been proposed all over the world. On August 6, 2012, Mars Science Laboratory mission landed the Martian ground successfully. However, the design margin had to be quite large because of the lack of knowledge of the aerothermochemistry. 1 In order to predict the radiation heating during the Martian atmospheric entry, several researchers have investigated these phenomena with experimental and simulated methods. B. A. Cruden, et al, have been measured the emission intensities behind strong shock wave with Mars (96% CO 2 , 4% N 2 ) and Venus (96.5% CO 2 , 3.5% N 2 ) simulant gases at downstream pressures and incident velocities spanning from 0.1-2.0 Torr and 3-12 km/s. 2,3 In our research group, the absolute radiation intensities behind strong shock wave in Martian simulant gas have been measured in our Hyper Velocity Shock Tube. 4 Emission intensities from VUV to NIR region were obtained at 1.0 Torr, 7km/s and 0.1 Torr, 8.5km/s. The absolute spectral radiances from UV to NIR and VUV to UV regions were calibrated with a tungsten halogen lamp and a Deuterium lamp, respectively. CO 4 th positive band in VUV, CN violet in UV and C 2 swan band in VIS were detected. Atomic carbon, nitrogen, and oxygen were also detected. At 1.0 Torr, 7km/s, the flow was achieved in thermochemical equilibrium around 5 mm behind the shock wave, while at 0.1 Torr, 8.5km/s, the flow was totally in nonequilibrium. The observed radiation intensities were same orders of magnitude with the ones measured in EAST facility.Fujita, K., et al., assessed forebody and aftbody heat transfer rates of a small-sized Martian aerocapture demonstrator for the preliminary design study of an aeroshell equipped with light-weight thermal protection system. 5 In the forebody region, a major portion of the spectrum is distributed among VUV and UV