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 hightemperature 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 0.35-0.7 μm, and the near-infrared band of 0.9-1.4 μm was unavailable.

Observation Capability Evaluation Model for Flood-Observation-Oriented Satellite Sensor Selection

“…Table 11 illustrates the qualitative comparative results between the OCEM and seven other methods, including the DOCI, sensor static capability index (SSCI) [25], sensor observation capability association ontology (SOCA Ontology) [58], sensor observation capability object field (SOCO-Field) [15], star sensor observation capability evaluation model (SSOCEM) [32], Earth observation potential evaluation model (EOPEM) [33], and sensor band selection method (SBSM) [11]. An overview of these methods is included in the final column of the table.…”

“…To pre-evaluate the observation capability in a quantitative manner, Chen and Zhang [29] proposed the dynamic observation capability index (DOCI) model to quantify the observation capability of optical satellite sensors, which can be dynamically applied in various emergencies, such as snowfall and oil spills. Liu et al [30], Zhang et al [31], and Chen et al [32] constructed a series of observation-task-oriented indicators, such as time utilization ratio and observed profit ratio, to quantitatively pre-evaluate the sensor observation capability. Jin et al [33] conducted a quantitative evaluation of the Earth observation satellite sensors' multidimensional observation capabilities (e.g., satellite orbit and spatial resolution) to assess their potential in supporting sustainable development goals.…”