Atmospheric Transmission Research Articles

Updated Forecast for TRAPPIST-1 Times of Transit for All Seven Exoplanets Incorporating JWST Data

The TRAPPIST-1 system has been extensively observed with JWST in the near-infrared with the goal of detecting atmospheric transit transmission spectra of these temperate, Earth-sized exoplanets. A byproduct has been much more precise times of transit compared with prior available data from Spitzer, Hubble Space Telescope, or ground-based telescopes. In this note we use 23 new timing measurements of all seven planets in the near-infrared from five JWST observing programs to better forecast and constrain the future times of transit in this system. In particular, we note that the transit times of TRAPPIST-1h have drifted significantly from a prior published analysis by up to tens of minutes. Our newer forecast has a higher precision, with uncertainties ranging from 7 to 105 s during JWST Cycles 4 and 5. This forecast will help to improve planning of future observations of the TRAPPIST-1 planets, while we postpone a full dynamical analysis to future work.

Physics-Driven Image Dehazing from the Perspective of Unmanned Aerial Vehicles

Drone vision is widely used in change detection, disaster response, and military reconnaissance due to its wide field of view and flexibility. However, under haze and thin cloud conditions, image quality is usually degraded due to atmospheric scattering. This results in issues like color distortion, reduced contrast, and lower clarity, which negatively impact the performance of subsequent advanced visual tasks. To improve the quality of unmanned aerial vehicle (UAV) images, we propose a dehazing method based on calibration of the atmospheric scattering model. We designed two specialized neural network structures to estimate the two unknown parameters in the atmospheric scattering model: the atmospheric light intensity A and medium transmission t. However, calculation errors always occur in both processes for estimating the two unknown parameters. The error accumulation for atmospheric light and medium transmission will cause the deviation in color fidelity and brightness. Therefore, we designed an encoder-decoder structure for irradiance guidance, which not only eliminates error accumulation but also enhances the detail in the restored image, achieving higher-quality dehazing results. Quantitative and qualitative evaluations indicate that our dehazing method outperforms existing techniques, effectively eliminating haze from drone images and significantly enhancing image clarity and quality in hazy conditions. Specifically, the compared experiment on the R100 dataset demonstrates that the proposed method improved the peak signal-to-noise ratio (PSNR) and structure similarity index measure (SSIM) metrics by 6.9 dB and 0.08 over the second-best method, respectively. On the N100 dataset, the method improved the PSNR and SSIM metrics by 8.7 dB and 0.05 over the second-best method, respectively.

High transmission efficiency long-wave infrared multispectral modulation array based on nanogap engineering

The long-wave infrared spectrum’s unique advantages in molecular fingerprinting and atmospheric transmission have led to its widespread application in detection, identification, medical diagnosis, and environmental monitoring. Consequently, there has been a strong focus on developing multispectral structure arrays with high transmission efficiency. In this study, we introduce a high-transmission-efficiency nanocoaxes field enhancement structures array based on complex nanogap engineering, exhibiting a transmission of 21.59 % within an open area of 3 % and accompanied by a 90-fold enhancement of the nanogap field. With the modulation of nanogaps, the absolute transmission can exceed 60 %. The experimental data and finite element simulation results of the spectrally tunable array confirm that the origin of resonance is attributed to the enhanced localized electromagnetic modes supported by nanogaps. Furthermore, we demonstrated the proposed nanocoaxes field-enhancement structures in practical applications such as molecular resonance absorption enhancement and material composition analysis. Our work not only provides a method for on-chip multispectral tuning in the long-wave infrared range but also contributes to further advancing the development of long-wave infrared nanophotonic structures.

Multi-field coupling analysis of photovoltaic cells under long distance and multi-mode laser transmission

Most electronic devices are powered by electricity, and the transfer of energy to related electronic devices is a critical issue. Laser wireless power transmission (LWPT) has a broad prospect in the field of wireless energy transmission, such as distributed charging system (DLC), spacecraft sensor network, satellite-to-satellite communication and medium and long distance power transmission, ground to unmanned aerial vehicle (UAV), and so on. In this paper, a multi-field coupled model of LWPT system for laser transmission at medium and long distances is established. Through the existing LWPT experimental platform and test, the test obtained the correlation coefficient of the I-V relationship formula with the change of light intensity and temperature. On the basis of the modified parameters, the attenuation efficiency of laser power with transmission distance is calculated, and the heat transfer and electrical characteristics of photovoltaic cells are solved by finite element method. It is found that different atmospheric environment and laser transmission distance have obvious effects on the voltage, current and temperature variation of photovoltaic cells. The temperature of a photovoltaic cell has a huge impact on its output efficiency. The temperature can be controlled effectively by setting the laser interval of pulse mode reasonably. The cooling capacity of photovoltaic cells is the key to improve the electrical conversion efficiency of LWPT systems.

Unipolar quantum optoelectronics for high speed direct modulation and transmission in 8–14 µm atmospheric window

The large mid-infrared (MIR) spectral region, ranging from 2.5 µm to 25 µm, has remained under-exploited in the electromagnetic spectrum, primarily due to the absence of viable transceiver technologies. Notably, the 8–14 µm long-wave infrared (LWIR) atmospheric transmission window is particularly suitable for free-space optical (FSO) communication, owing to its combination of low atmospheric propagation loss and relatively high resilience to turbulence and other atmospheric disturbances. Here, we demonstrate a direct modulation and direct detection LWIR FSO communication system at 9.1 µm wavelength based on unipolar quantum optoelectronic devices with a unprecedented net bitrate exceeding 55 Gbit s−1. A directly modulated distributed feedback quantum cascade laser (DFB-QCL) with high modulation efficiency and improved RF-design was used as a transmitter while two high speed detectors utilizing meta-materials to enhance their responsivity are employed as receivers; a quantum cascade detector (QCD) and a quantum-well infrared photodetector (QWIP). We investigate system tradeoffs and constraints, and indicate pathways forward for this technology beyond 100 Gbit s−1 communication.

Co2+-doped ErBO3 microspheres as high-efficiency laser absorption at 1540 nm wavelength

1540 nm lasers are widely used for excellent anti-interference capability and atmospheric transmission, whose corresponding suppressing materials are still lack of investigation Er3+ ions can effectively absorb 1540 nm lasers due to energy level transitions near this wavelength. And the absorption effect could be further enhanced by doping with heterogeneous metal ions. Herein, Co2+ has been doped into ErBO3 with different concentrations, which could induce lattice contraction of Er3+ ion cells. The ErBO3 samples prepared by solvothermal and calcination processes are characterized by “flower-like” porous microspheres at 800 °C. The influence of different calcination temperatures and molar ratios of raw materials on the reflection performance of 1540 nm laser light was examined. The laser reflectance of the sample was reduced to 0.707 % by doping with 20 mol% Co2+. This Co2+ doped ErBO3 material exhibits significant potential in 1540 nm laser protection applications.

The Influence of Different Phase Function Combinations on Communication Quality in NLOS Communication Model

Wireless ultraviolet communication is a new type of communication technology, which uses the atmosphere as the transmission medium, and uses the scattering effect of atmospheric molecules and aerosol particles to change the propagation direction of the optical signal carrying information, bypass the blocking obstacles and finally reach the receiving end. The study of the scattering characteristics of ultraviolet light requires the use of scattering phase function. The scattering phase function is the ratio of the scattering energy in the unit solid angle in a specific direction to the average scattering energy in all directions. The scattering of ultraviolet light by the atmosphere is usually divided into two cases : Rayleigh scattering and Mie scattering. Therefore, the scattering phase function is also divided into two cases : Rayleigh scattering phase function and Mie scattering phase function. The scattering phase function in this paper is obtained by the weighted average of the two. There are many empirical formulas for Rayleigh scattering phase function and Mie scattering phase function. In this paper, the ultraviolet light of 266 nm wavelength is taken as an example to simulate and analyze the variation trend of scattering coefficient with wavelength and visibility, and the influence of the combination of different scattering phase functions on the received light power per unit area in the process of ultraviolet atmospheric transmission.

Multi-spectrum compatible electrochromic device combining microwave transmission with ultra-wide emissivity modulation

The potential of polyaniline (PANI)-based electrochromic devices (ECDs) to offer adaptive anti-surveillance stealth in the visible/infrared bands is considerable. However, the incompatibility between infrared and radar stealth renders it challenging to achieve compatibility between the two with PANI-based ECDs. In this work, an etched electrode with frequency-selective surface configurations is initially designed for selective transmission and reflection of microwaves. Subsequently, a stellate PANI is prepared on the electrode surface by introducing triphenylamine (TPA) modification into the long molecular chain of disordered PANI, and assembled into a multi-spectrum compatible ECD. The results demonstrate that the ECD can achieve efficient transmission between 10.2–13.9 GHz, with a transmission rate approaching 90 % at 11.92 GHz, and enables the visible characteristics to switch between jungle dark green and desert earthy yellow. Furthermore, thermal-infrared emissivity (ε) modulation is achieved in the atmospheric transmission windows of 3–5 μm and 8–14 μm, with maximum emissivity change (Δε) of 0.61 and 0.73, respectively. The ECD demonstrated the capacity to exceed the limitations of static camouflage associated with existing multi-spectrum stealth materials, and exhibited a high degree of adaptability in intelligent electromagnetic confrontation environments.

Development of Polarization-Insensitive THz-to-IR Converters for Low-IR-Signature Target Detection and Imaging.

A THz-to-IR converter can be an effective solution for the detection of low-IR-signature targets by combining the advantages of mature IR detection mechanisms with high atmospheric transmittance in the THz region. A metallic metasurface (MS)-based absorber with linear polarization dependence based on a split-ring resonator (SRR) unit cell has been previously studied as a preliminary example of a THz-to-IR converter structure in the literature. In this simulation-based study, a new cross-shaped unit cell-based metallic MS absorber structure sensitive to dual polarization is designed to eliminate linear polarization dependency, thereby allowing for incoherent detection of THz radiation. A model is developed to calculate the temperature difference and the response time for this new cross-shaped absorber structure, and its performance is compared to the SRR structure for both coherent and incoherent illumination. This model allows for understanding the efficiency of these structures by considering all loss mechanisms which previously had not been considered. It is found that both structures show similar performance under linearly polarized coherent illumination. However, under incoherent illumination, the IR emittance efficiency as gauged by the temperature difference for the cross-shaped structure is found to be twice as high as compared to the SRR structure. The results also imply that calculated temperature differences for both structures under coherent and incoherent illumination are well above the limit of the minimum resolvable temperature difference of the state-of-the-art IR cameras. Therefore, dual-polarized or multi-polarization-sensitive MS absorber structures can be crucial for developing cost-effective THz-to-IR converters and be implemented in THz imaging solutions.

Research on integrated LiDAR and multi-parameter detection of atmospheric transmittance, turbulence, and wind

An integrated LiDAR system has been reported, which can be used for simultaneous detection of atmospheric transmittance, turbulence, and wind along the same path. Through the integrated design of optics and mechanics, the size and weight of the system were effectively reduced. The comprehensive detection distance of atmospheric transmittance, atmospheric coherence length, and radial wind had also been achieved at least 4 kilometers. Comparative experiments have demonstrated that the detection results of the integrated LiDAR system and the near-surface meteorological observation system have standard deviations of less than 0.03 km−1 for extinction coefficient, 0.2 m/s for wind velocity, and 7.15 × 10−14 m−2/3 for C 2 n (atmospheric refractive index structure parameter), thus verifying the accuracy of the system detection. The reliability of the integrated LiDAR system was validated through six consecutive nights of continuous detection experiments, measuring three parameters simultaneously. Through analysis, the influence laws among atmospheric transmittance, coherence length, and wind were preliminarily explored. Significant variations in wind velocity can induce substantial fluctuations in atmospheric coherence length, and it is positively correlated with atmospheric transmittance. The integrated LiDAR system can provide a variety of reliable real-time detection data for further research on the laser transmission process in the atmosphere.

Tracing the physical signatures among the calculated global clear-sky spectral shortwave radiative flux distribution

This study utilized the high-spectral resolution radiative transfer model (MODerate resolution atmospheric TRANsmission, MODTRAN6.0.2.5) to compute global clear-sky shortwave (SW) radiative flux and compared it with NASA’s Clouds and the Earth’s Radiant Energy System (CERES) Synoptic Radiative Fluxes and Clouds (SYN1deg) product. The comparison revealed that the global distributions of clear-sky downwelling SW fluxes at the surface from the M6.0 calculations and SYN1 results are similar, with annual means of 246.51 Wm-2 and 242.42 Wm-2, respectively. Analysis further showed that most of the M6.0 calculations are slightly higher from low to mid-latitudes, particularly in the Northern Hemisphere (NH), but lower in higher latitudes compared to SYN1 results. However, these differences mostly fall within the CERES estimated uncertainty (6 Wm-2) of monthly mean clear-sky downwelling SW flux at the surface. The sensitivity of clear-sky SW/μ0 fluxes to changes in Precipitable Water Vapor (PWV), represented by the clear-sky water vapor radiative kernel, is about -0.7 Wm-2/(kgm-2) over oceans for both M6.0 and CERES SYN1 products, except for SYN1 results over the Southern Hemisphere (SH) ocean. Additionally, the zonal means of land coverage and SW/VIS/NIR albedos from M6.0 calculations indicate that VIS albedos are highest in polar regions (>60°), followed by SW and NIR albedos, while NIR albedos become highest from low to mid-latitudes (<60°). Generally, SW/VIS/NIR albedos and their differences increase monotonically with increased land coverage from 60°S to 60°N. The consistent clear-sky water vapor radiative kernels derived from both products exceeded our expectations, suggesting their potential use to trace physical signatures in climate model calculations. It is recommended that these model-derived radiative kernels should be validated by the long-term global and regional surface observations in order to enhance confidence to implement these radiative kernels in climate models.

In-situ ETEM study of plasma-facing tungsten nanofuzz oxidation at atmospheric pressure: Microstructure evolution and substrate-free oxidation kinetics

To enable sustainable carbon-free fusion energy, managing reactor structural material degradation during normal operation as well as accident scenarios is vital. Tungsten (W) plasma-facing materials (PFMs) are susceptible to aggressive high-temperature oxidation during air-ingress fusion reactor accidents, yet there's a lack of oxidation kinetic data for irradiated tungsten. Here, we utilize atmospheric environmental transmission electron microscopy (ETEM) to present the first kinetic data for substrate-free W nanofuzz oxidation at 400 °C and 500 °C in 1 bar dry air. Comparison with pristine bulk W during the early parabolic stage suggests an irradiation-decelerated oxidation for W nanofuzz. Our time-resolved in-situ characterization reveals a durable amorphous surface oxide, likely promoted by high-flux He+ irradiation-induced surface defects, serving as an effective passivating layer that impedes nanofuzz oxidation onset. This surface oxide layer also interfaces well with newly formed orthorhombic WO3, facilitated by stress relief through He bubble shrinkage, providing lasting passivating protection throughout the nanofuzz parabolic oxidation. This new finding challenges conventional notions of irradiation's negative impact on metal oxidation, and calls for advanced characterization to enhance our understanding of fusion energy materials degradation, informed by further accident modeling.

Remote sensing of H2O/HDO in the atmospheric column based on a near-infrared laser heterodyne radiometer suppressing local oscillator relative intensity noise

Laser heterodyne radiometer (LHR) exploits the heterodyne signal generated by solar radiation beated with local oscillator (LO) light to extract information on atmospheric species in the atmospheric column. Most of currently reported LHRs are affected by LO-induced relative intensity noise (RIN), which poses a challenge for high-sensitivity detection. In this work, a near-infrared RIN-suppressed LHR is proposed for simultaneous detection of water vapor and HDO in the atmospheric column. The operability of a home-made sun tracker can be obtained from coarse tracking and fine tracking, which offers an excellent opportunity for unattended observation. A tunable distributed feedback (DFB) diode laser centered at 1552.9 nm is employed as LO, where LO-induced RIN is suppressed by a semiconductor optical amplifier (SOA) operating in the dynamic gain saturation regime. By locking LO power and suppressing LO-induced RIN, the SOA-assisted LHR is dominated by 1.27 times shot-noise and the signal-to-ratio (SNR) of heterodyne signal is increased by 5 times. Based on atmospheric transmission spectra measured with the RIN-suppressed LHR in Hefei, China, the total column abundances of water vapor and HDO are retrieved to be 2050 ppm and 0.6 ppm, respectively, with uncertainty of 2 %.

Spatial variation, emissions, transport, and risk assessment of organophosphate esters in two large petrochemical complexes in southern China

Organophosphate esters (OPEs) serve as significant flame retardants and plasticizers in various petrochemical downstream products. The petrochemical industry could be a potential source of atmospheric OPEs, but their emissions from this industry are poorly understood. The present study revealed the spatial variation, emission, and atmospheric transport of traditional and novel OPEs (TOPEs and NOPEs, respectively) in atmospheric particulate matter (PM) across Hainan and Guangdong petrochemical complexes (HNPC and GDPC, respectively) in southern China. The total concentrations of TOPEs ranged from 232 to 46,002 pg/m3 and from 200 to 20,347 pg/m3 in the HNPC and GDPC, respectively, which were substantially higher than those of NOPEs (HNPC: 23.5−147 pg/m3, GDPC: 13.9−465 pg/m3). Enterprises involved in the production of downstream petrochemical products presented relatively high concentrations of OPEs, indicating evident emissions of these pollutants in the petrochemical industry. The correlations of PM-bound OPEs in the atmosphere are determined mainly by their coaddition to industrial products or their coexistence in technical mixtures. The annual emissions of TOPEs and NOPEs in the HNPC were 42.6 kg and 0.34 kg, respectively, and those in the GDPC were 116 kg and 1.85 kg, respectively. OPEs from the HNPC can reach Vietnam, Cambodia, and Guangxi Province, China, and those from the GDPC can reach Guangxi Province and Hunan Province via atmospheric transmission after 24 h of emission. The OPE concentrations reaching the receptor regions were generally less than 3.20 pg/m3. Risk assessment revealed that OPE inhalation exposure on two petrochemical complexes likely poses minor risks for people living in the study areas, but the risk resulting from two chlorinated OPEs should be noted since they are close to the threshold values. This study has implications for enhancing control measures for OPE emissions to reduce health risks related to the petrochemical industry.

A Geant4 Monte Carlo toolkit-based radiative transfer model for studying the impact of aerosols

Radiative transfer models are of prime importance in quantifying the earth-atmosphere energy budget. A radiative transfer model based on the Geant4 Monte Carlo toolkit was developed. This model is able to perform calculations of the spectral atmospheric transmittance, surface solar irradiance, as well as the Top of the Atmosphere (TOA) reflected irradiance over the spectral range from 280 nm to 3000 nm. Through this study, the Geant4 toolkit was used to study the effect of rural aerosols concentration on different radiative characteristics. Geant4 radiative calculations in the presence and absence of aerosols were compared to that of DISORT code. For both surface and Top of the atmosphere simulations, good agreement was observed between the two models. Specifically, under atmospheric visibility conditions of 23 km, the mean relative difference between Geant4 and DISORT code was found to be less than 2.46 % for Global irradiance calculations and less than 7.9 % for TOA reflected irradiance. A comparative analysis between the measured total global irradiance in Adrar city and the irradiance estimated by Geant4 demonstrated the general effectiveness of Geant4, with a coefficient of determination of 0.991 and a Mean Absolute Percentage Error (MAPE) of 5.851 %.

Why Observations at Mid-infrared Wavelengths Partially Mitigate M Dwarf Star Host Stellar Activity Contamination in Exoplanet Transmission Spectroscopy

Exoplanet atmosphere transmission spectroscopy for planets orbiting M dwarf stars faces significant challenges due to contamination from stellar magnetic features, i.e., spots and faculae. These features make the stellar surface inhomogeneous and introduce wavelength-dependent signals in the transmission spectrum that complicate its analysis. We identify and explain why using observations at infrared wavelengths greater than a few microns partially mitigates stellar contamination. At these wavelengths the intensity sensitivity to temperature weakens, with two significant consequences. First, the contribution of spots and faculae has a diminished effect because their flux contrast to the quiet-star regions lessens. Second, the star’s spectral features compress in magnitude, an outcome of spectral features being shaped by the star’s photospheric vertical temperature gradient. Both factors are due to the Planck function moving from exponential to linear in temperature toward mid-infrared (mid-IR) wavelengths (the “Rayleigh–Jeans tail”). In contrast to stellar spectra, the depth of the transmission spectroscopy features does not fundamentally vary with wavelength as it is primarily determined by the planet’s atmospheric scale height. The magnitude of reduction in stellar contamination is a factor of a few to several at mid-IR versus near-IR wavelengths, but whether or not this is enough to bypass stellar contamination ultimately depends on the spot coverage area. Nonetheless, the flattening of thermal emission spectral features at IR wavelengths is universal.

StarDICE II: Calibration of an Uncooled Infrared Thermal Camera for Atmospheric Gray Extinction Characterization.

The StarDICE experiment strives to establish an instrumental metrology chain with a targeted accuracy of 1 mmag in griz bandpasses to meet the calibration requirements of next-generation cosmological surveys. Atmospheric transmission is a significant source of systematic uncertainty. We propose a solution relying on an uncooled infrared thermal camera to evaluate gray extinction variations. However, achieving accurate measurements with thermal imaging systems necessitates prior calibration due to temperature-induced effects, compromising their spatial and temporal precision. Moreover, these systems cannot provide scene radiance in physical units by default. This study introduces a new calibration process utilizing a tailored forward modeling approach. The method incorporates sensor, housing, flat-field support, and ambient temperatures, along with raw digital response, as input data. Experimental measurements were conducted inside a climatic chamber, with a FLIR Tau2 camera imaging a thermoregulated blackbody source. The results demonstrate the calibration effectiveness, achieving precise radiance measurements with a temporal pixel dispersion of 0.09 W m-2 sr-1 and residual spatial noise of 0.03 W m-2 sr-1. We emphasize that the accuracy of scene radiance retrieval can be systematically affected by the camera's close thermal environment, especially when the ambient temperature exceeds that of the scene.

Simultaneous thermal camouflage and radiative cooling for ultrahigh-temperature objects using inversely designed hierarchical metamaterial

Abstract Sophisticated infrared detection technology, operating through atmospheric transmission windows (usually between 3 and 5 μm and 8–13 μm), can detect an object by capturing its emitted thermal radiation, posing a threat to the survival of targeted objects. As per Wien’s displacement law, the shift of peak wavelength towards shorter wavelengths as blackbody temperature rises, underscores the significance of the 3–5 μm range for ultra-high temperature objects (e.g., at 400 °C), emphasizing the crucial need to control this radiation for the objects’ viability. Additionally, effective heat management is essential for ensuring the consistent operation of these ultrahot entities. In this study, based on a database with high-temperature resist materials, we introduced a material-informatics-based framework aimed at achieving the inverse design of simultaneous thermal camouflage (low emittance in the 3–5 μm range) and radiative cooling (high emittance in the non-atmospheric window 5–8 μm range) tailored for ultrahigh-temperature objects. Utilizing the transfer matrix method to calculate spectral properties and employing the particle swarm optimization algorithm, two optimized multilayer structures with desired spectral characteristics are obtained. The resulted structures demonstrate effective infrared camouflage at temperatures up to 250 °C and 500 °C, achieving reductions of 86.7 % and 63.7 % in the infrared signal, respectively. At equivalent heating power densities applied to the structure and aluminum, structure 1 demonstrates a temperature reduction of 29.4 °C at 0.75 W/cm2, while structure 2 attains a temperature reduction of 57.5 °C at 1.50 W/cm2 compared to aluminum, showcasing enhanced radiative cooling effects. This approach paves the way for attenuating infrared signals from ultrahigh-temperature objects and effectively managing their thermal conditions.

Amorphous Gallium Oxide-Based Crosstalk-Suppressing Solar-Blind Imaging Array Prepared by One-Step Method.

The solar-blind ultraviolet band presents a unique opportunity for low-background-noise detection due to limited atmospheric light transmission. Especially, with the ability to obtain size, shape and position information on the objects, the solar-blind image sensors are receiving increasing attention. However, because the inhibition of the crosstalk in crossbar arrays induces the complexity of the preparation process, rarely are applicable solar-blind UV imaging arrays reported. This work prepared an amorphous gallium oxide (a-Ga2O3)-based diode with a remarkable rectifier ratio of up to 106. Then an imaging array was prepared by one-step method in that the diodes working as the detection elements and the switching elements inhibiting crosstalk were simultaneously deposited. Moreover, a 2 × 2 crossbar array clearly demonstrates the inhibition of the crosstalk. This work presents a simple and cost-effective method for preparing applicable solar-blind imaging arrays that inhibits crosstalk, promoting the practical application of the Ga2O3-based solar-blind UV detectors.

Effects of Aluminum/Carbon and Morphology on Optical Characteristics and Radiative Forcing of Alumina Clusters Emitted by Solid Rockets in the Stratosphere

Alumina (Al2O3) particles, the primary combustion products of solid rockets, can accumulate in the stratosphere, changing the global radiative balance. These Al2O3 particles were usually treated as homogeneous spheres. However, they contain impurities and may form clusters during the combustion process. Models representing Al-containing and C-containing Al2O3 clusters were developed, denoted as Al2O3 shell model (ASM) and Al2O3 core model (ACM), respectively. The superposition T-matrix method (STMM) was applied to examine their optical characteristics. Subsequently, a method to obtain the top-of-atmosphere flux was proposed by integrating the models with the moderate resolution atmospheric transmission code (MODTRAN). With the addition of Al/C, the absorption cross-section enhances by several orders of magnitude at 0.55 μm and increases slightly at 10 μm. The equivalent sphere models will weaken their scattering ability. A 4Tg mass burden of Al2O3 produces radiative forcing of −0.439 Wm−2. However, the addition of Al and C reduces the forcing by up to 15% and 12%, respectively. In summary, the optical characteristics and radiative forcing of Al2O3 clusters are sensitive to Al/C and morphology models. While our findings are impacted by various uncertainties, they contribute valuable insights into the radiative forcing of Al2O3 particles, potential climatic changes by space activities.