An Evaluation Model of Star Sensor Observation Capability Under Hypersonic Aerothermal Conditions

Abstract

During hypersonic flight in the atmosphere, severe aerothermal effects occur on the optical hood or observation window of an aircraft, keeping the optical window and surface flow field in a high-temperature state, as well as causing a large amount of radiation and strong background noise. These phenomena have serious effects on the observation capability of star sensors. An evaluation model of star sensor observation capability under hypersonic aerothermal conditions was constructed in this study, using a definition of the signal-to-noise ratio considering defocused intense radiation sources. Furthermore, a method of calculating the observable limiting magnitude under aerothermal conditions is given. The model was used in simulation tests involving different flight states and temperature conditions. The results showed that the thermal radiation of the aircraft observation window has the greatest influence, which is more than two orders higher than that of the outer flow near the window; when the window temperature was controlled below 750 K, for a star sensor with an SNR threshold of 3, navigation stars with magnitudes brighter than 5 could be captured in the visible band of 0.35– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.7~\mu \text{m}$ </tex-math></inline-formula> , and the near-infrared band of 0.9– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.4~\mu \text{m}$ </tex-math></inline-formula> was unavailable.