Spectroscopic Observation of the Re-Entry Capsule of HAYABUSA Spacecraft

Abstract

Abstract We performed low-resolution spectroscopic observations of the capsule of the HAYABUSA spacecraft during re-entry into the Earth's atmosphere on 2010 June 13 UT as an artificial meteor. We obtained the photometric magnitude of the HAYABUSA capsule using zeroth-order spectra. The efficiency of the zeroth-order spectra was too low for us to measure the magnitude of the capsule without any saturation at all times. The altitude at the maximal flux of the capsule was at around 56 km (13$^{\rm h}$52$^{\rm m}$19$\!\!\!^{\rm s}$81 UT), which is almost similar to the case GENESIS, i.e., the maximal flux at around 55 km. We examined the change in the spectrum shape of the capsule as a function of its altitude, and investigated the emission from the shock layer and the blackbody radiation from the surface of the capsule. It is found that the shock-layer emission was dominant, and/or on the same order of the blackbody radiation at the early phase of re-entry; also, the emission from blackbody radiation was dominant during the last phase of re-entry. We measured the surface temperature of the capsule along the trajectory; during the last phase before dark flight, we found that the blackbody temperature of the capsule was 3100$\ \pm\ $300 K at an altitude of around 50 km, and 2400$\ \pm\ $300 K at an altitude of around 40 km.