NLTE-based atmospheric radiance modeling for space-based 4.3μm infrared detection of rocket exhaust flames

Area of Science:

• Atmospheric physics and remote sensing
• Aerospace engineering and detection systems

Background:

• Accurate atmospheric radiance modeling is essential for detecting rocket exhaust flames.
• Traditional Local Thermodynamic Equilibrium (LTE) models are insufficient at high altitudes (above 50 km) where Non-Local Thermodynamic Equilibrium (NLTE) conditions prevail.

Purpose of the Study:

• To develop a space-based background radiance model for rocket exhaust flame detection.
• To analyze the impact of NLTE effects on infrared radiance contrast at 4.3μm.
• To assess the detectability of rocket exhaust flames using narrow-band infrared detection from geosynchronous orbit.

Main Methods:

• Coupling remote sensing data with an NLTE atmospheric model.
• Analyzing radiance contrast of rocket exhaust flames against cloud backgrounds.
• Investigating narrow-band detectability within the 4.3μm infrared band.

Main Results:

• NLTE significantly affects atmospheric radiance and transmittance.
• NLTE conditions reduce the infrared radiance contrast of rocket exhaust flames.
• The NLTE effect must be considered for accurate space-based background radiance modeling.

Conclusions:

• The study highlights the critical role of NLTE in high-altitude atmospheric radiance.
• Ignoring NLTE effects can lead to underestimating detection challenges for rocket exhaust flames.
• This research supports the development of robust infrared detection systems for space-based applications.