arXiv:2605.22268v1 [cs.NI] 21 May 2026
Impact of Atmospheric Turbulence and Pointing Error on Earth Observation Celia Sánchez-de-Miguel
Antonio M. Mercado-Martı́nez
Beatriz Soret Senior Member, IEEE
TELMA, University of Malaga Malaga, Spain [email protected]
TELMA, University of Malaga Malaga, Spain [email protected]
TELMA, University of Malaga Malaga, Spain [email protected]
Antonio Jurado-Navas Member, IEEE
Miguel Castillo-Vázquez Member, IEEE
TELMA, University of Malaga Malaga, Spain [email protected]
TELMA, University of Malaga Malaga, Spain [email protected]
Abstract—Earth Observation (EO) imagery is often degraded by atmospheric turbulence and pointing jitter; yet, these effects are rarely considered in datasets used to train AI-based detection models. Based on prior work, this paper presents an enhanced image simulator that enables the incorporation of vertical-path atmospheric turbulence and satellite pointing jitter, arising from platform and sensor vibrations, to generate physically realistic distorted images. As a case study, vessel detection is evaluated using YOLOv8 and RetinaNet on images generated by the proposed simulator under different levels of turbulence and pointing errors. Results show that YOLOv8 recall decreases from 91% under ideal conditions to 60% in the presence of weak turbulence, and falls below 40% under strong turbulence or jitter. In contrast, RetinaNet demonstrates greater robustness, maintaining approximately 75% recall across degraded conditions. These results highlight the importance of incorporating realistic physical degradations into EO training datasets to ensure reliable performance of AI-based models in operational environments, as demonstrated in maritime surveillance applications. Index Terms—Maritime surveillance, Earth observation, LEO satellites, object detection, deep learning, YOLO, RetinaNet, atmospheric turbulence, jitter.
I. I NTRODUCTION Earth Observation (EO) satellites play a critical role in sustainability applications such as environmental monitoring and disaster response, as well as maritime surveillance, border security, and vehicle tracking [1]. The effectiveness of All the authors are with the Telecommunications Research Institute (TELMA), Universidad de Málaga, 29071, Málaga, Spain. The work is partially supported by ESA SatNEx V (prime contract no. 4000130962/20/NL/NL/FE), and by the Spanish Ministerio de Ciencia e Innovación under grant PID2022-136269OB-I00 funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe”. The view expressed herein can in no way be taken to reflect the official opinion of the European Space Agency. The work of A.M. Mercado-Martı́nez is also partially supported by Grant DGP PRED 2024 01603, funded by the Consejerı́a de Universidad, Investigación e Innovación of Junta de Andalucı́a and the European Union. The work of C. Sánchez-de-Miguel is also partially supported by Grant DGP PRED 2024 02392, funded by the Consejerı́a de Universidad, Investigación e Innovación of Junta de Andalucı́a and the European Union. The authors thankfully acknowledge the computer resources, technical expertise and assistance provided by the SCBI (Supercomputing and Bioinformatics) center of the University of Málaga.
these applications depends on the ability to reliably extract information from satellite imagery, which in turn requires robust detection and classification algorithms. For instance, timely ship detection can assist in combating illegal fishing, piracy, and maritime accidents [2]; accurate monitoring of urban growth supports sustainable development policies [3]; and rapid damage assessment after natural disasters enables efficient emergency response [4]. Despite their importance, EO images are often degraded by physical phenomena such as cloud coverage, pointing errors, and atmospheric turbulence. While cloud coverage is frequently addressed in dataset preparation, turbulenceinduced distortions and spacecraft-induced pointing jitter are largely neglected in existing datasets. This omission is problematic. Turbulence leads to spatial blurring and image distortions, while jitter causes misalignment and pixel misregistration—both of which can drastically reduce the performance of AI-based detection systems in real operational conditions. Most public EO datasets used for training AI models assume clear and stable imaging conditions. Consequently, their performance may exhibit significant degradation when applied to real-world imagery affected by turbulence and jitter. This limits their applicability in mission-critical scenarios such as maritime surveillance, where false negatives in vessel detection may have severe economic, environmental, or security implications. In this work, we build upon and extend the analysis presented in [5], where semantic communication concepts were introduced for EO scenarios. Specifically, we further investigate the impact of atmospheric turbulence on optical satellite imagery and incorporate platform-induced pointing jitter to obtain a more realistic assessment of detection performance. By extending the Zernike-based turbulence simulator proposed in [6], we generate distorted images that better capture operational degradations. These synthetic yet realistic images can be used both for training and for evaluating AIbased detection models under realistic conditions. As a case study, we apply our framework to the training
EO satellite
LEO constellation distorted image
distorted wavefront
Atmospheric turbulence non-distorted image
GS
Earth
Fig. 1: Scenario with a single LEO satellite and the presence of atmospheric turbulence. and testing of a YOLOv8 vessel detection model [7], and compare its performance against RetinaNet [8]. YOLOv8 has been selected as it is a well-established detection algorithm that provides real-time inference with high accuracy and lower computational cost compared to other approaches such as RetinaNet and Mask R-CNN. Results show a substantial reduction in recall under turbulence and jitter scenarios, demonstrating the need to incorporate such physical effects in dataset generation. Beyond ship detection, the proposed approach can benefit a broad range of EO applications, including disaster monitoring, border surveillance, and precision agriculture, by providing more robust AI-based analytics in degraded imaging environments. The rest of this paper is organized as follows: Section II describes the considered EO scenario. Section III details the adopted image-distortion model. Section IV presents the performance evaluation and discusses the obtained results. Finally, Section V concludes the paper with final remarks. II. EO SCENARIO To illustrate our scenario in a realistic context, we consider a representative EO mission where a Low Earth Orbit (LEO) satellite captures high-resolution optical images of maritime regions. Such scenarios are of growing interest for vessel detection and tracking, illegal fishing prevention, and maritime safety operations. Figure 1 shows the observation setup of a LEO satellite equipped with a camera. As the satellite moves along its orbit, it acquires optical images of the Earth’s surface. Light reflected by objects on the Earth’s surface propagates upward through the atmosphere, where refractive index fluctuations distort the wavefront and degrade spatial resolution. In parallel, the imaging system is subject to mechanical vibrations and attitude instabilities that introduce pointing jitter, further blurring the acquired images. The resulting measurements therefore deviate from the ideal scene, complicating object detection and classification. Once the images are captured, the satellite establishes a line-of-sight (LOS) radio frequency (RF) link with a ground station (GS) to downlink the data. Object detection processing is assumed to be performed in the ground segment, with sufficient computational resources available to execute the required
algorithms. This configuration enables a direct assessment of how physical disturbances and transmission effects influence the overall performance of the detection system. The maximum achievable data rate for the RF link at time t depends on the received Signal-to-Noise Ratio (SNR), following Shannon capacity: Rt = B log2 (1 + SNRt ) ,
(1)
where B denotes the channel bandwidth. The instantaneous received SNR is given by SNRt = P GT GR /(Lp Lb σ 2 ) where P is transmit power; GT and GR are the transmitter and receiver parabolic antenna gains, respectively: σ 2 is the noise 2 power; Lp represent the pointing loss; and Lb = (4πdf /c) is the free-space path loss, Here, d is the instantaneous distance between the satellite and the GS, f is the carrier frequency, and c is the speed of light. The distance d is a function of the satellite orbital altitude and the elevation angle ε, and can be derived geometrically using the Pythagorean theorem. The volume of data to be transmitted scales with the captured area, the ground sampling distance (GSD), and the number of bits per pixel. For high-resolution optical payloads, this volume can easily exceed several hundred Mbps, making compression and on-board processing essential. In this context, capture conditions must be carefully considered, as they directly influence both algorithmic performance and transmission efficiency. More importantly, by modeling turbulence and jitter during the image acquisition stage, the proposed framework enables an end-to-end performance evaluation that accounts for both physical distortions and communication constraints in realistic EO missions. Thus, we can establish a threshold of turbulence that guarantees a satisfactory outcome when processing the data at ground. III. I MAGE D ISTORTION M ODEL In satellite imaging systems, the fidelity of the captured scene is influenced by both the propagation medium and the stability of the platform. In particular, atmospheric turbulence and pointing jitter are two critical impairments that directly impact the GSD and the spatial resolution of EO images. Their effects, often neglected in existing datasets, are crucial to model when assessing the robustness of AI-based detection algorithms. A. Atmospheric Turbulence Atmospheric turbulence, which gives rise to the phenomenon known as atmospheric scintillation, is primarily caused by temperature–and pressure–induced fluctuations in the refractive index of air [9]. These random variations distort both the amplitude and the phase of the received optical signal, making turbulence a fundamental limitation of FSO communication links [10]. In image systems, the same fluctuations distort the optical wavefront as light propagates through the atmosphere, resulting in scintillation, blur, and loss of contrast. The severity of these distortions depends on altitude, weather conditions, and time of day, and can be
where Zj (ρ) denotes the j-th Zernike polynomial, ρ = [ρ, θ]T is the normalized polar coordinate vector with 0 ≤ ρ ≤ 1 and Rρ = [Rρ, θ]T with R = D/2 being the aperture radius and D the lens diameter. The Zernike coefficients depend on D, the refractive index structure parameter Cn2 profile, the wavelength 2 2 λ, and the focal length f . The distorted wavefront Φ(Rρ) 0.49σR 0.51σR σI2 = exp 7/6 + 5/6 − 1, is then converted into a point spread function (PSF), which 12/5 12/5 1 + 0.56σR 1 + 0.69σR determines the effective blur applied to the image. (2) The simulator divides the input image into smaller blocks 2 where σR denotes the Rytov variance [9]. Since atmospheric and generates the corresponding PSF for each block. A spaturbulence is predominantly located in the lower layers of tially varying blur is then applied to the blocks, and the tilt 2 the atmosphere, σR tends to saturate with altitude. The corre- values are sampled according to the covariance matrix C, sponding end-to-end variance is calculated as [9]: warping the image based on turbulence-induced motion. Using the Hufnagel-Valley model, different values of Cn2 (h) 2 σR =2.25k 7/6 (H − h0 )5/6 sec(ζU )11/6 × are obtained for the propagation path.. Following [9], and after 5/6 5/6 Z H h − h h − h some mathematical manipulation, these values can be averaged 0 0 Cn2 (h) 1 − × dh, as: H − h H − h 0 0 h0 (3) 4.5 2 ∆h× < Cn >= H − h0 where k = 2π/λ represents the optical wave number, H is 5/6 5/6 ! H the orbital altitude, h0 is the height of the transceiver on the X h − h0 H −h 2 × Cn (h) , ground, ζU is the zenith angle of the propagation path and H − h0 H − h0 2 h=h 0 Cn (h) denotes the refractive index structure parameter and (7) describes turbulence strength at altitude h. Among existing models, the Hufnagel-Valley (HV) profile [9] is widely used, where ∆h denotes the altitude step used to compute the as it incorporates altitude, wind speed, and ground-level condi- average. The summation is evaluated over the discrete set of tions. In this work, the HV model has been adapted to include altitudes h = [h0 : ∆h : H] and the resulting average < C 2 > n a variable Cn2 (0), enabling the simulation of diurnal variations for the vertical path is then used as input to the simulator. in turbulence intensity. Thus: This framework allows the generation of physically characterized by the scintillation index σI2 . For vertical groundto-satellite propagation, the optical field is typically modeled as a spherical wave. In this case, the scintillation index is given by
Cn2 (h) =0.00594(w/27)2 (10−5 h)10 exp (−h/1000)+ −16
+ 2.7 × 10
exp (−h/1500) + A exp (−h/100), (4)
with w being the rms wind speed (pseudowind) in meters per second [m/s], and A a nominal value of Cn2 (0) at the ground in [m−2/3 ]. To emulate image distortions, we build upon the Zernikebased turbulence simulator of Chimitt and Chan [6], which avoids expensive wave-propagation calculations by sampling intermodal and spatially correlated Zernike coefficients, the latter reflecting the physical properties of atmospheric turbulence. Each coefficient corresponds to a specific aberration (e.g., tilt, defocus, astigmatism) and is generated from a multivariate Gaussian distribution with covariance matrix C, where the (j, j ′ )-th element is given by: [C]j,j ′ = E[a∗j aj ′ ].
(5)
Here E[·] denotes the expectation operator, aj and aj ′ are the Zernike coefficients, and j indexes the Zernike mode. The covariance matrix C captures the intermodal correlations between coefficients, ensuring that the sampled aberrations follow the statistical behavior of real atmospheric turbulence. The distorted wavefront is then reconstructed as Φ(Rρ) =
N X j=1
aj Zj (ρ)
(6)
grounded distortions consistent with atmospheric conditions at different altitudes and times of day. Compared to prior work, our contribution lies in extending the simulator to vertical paths, incorporating an altitude-dependent refractiveindex structure parameter Cn2 (h), and tailoring the model to EO imagery, where robustness of AI-based object detection is the primary concern. As an illustrative example, experimental ground-level measurements are used to define a cumulative distribution function (CDF) for Cn2 (0), as shown in Figure 2 highlighting the variability of this parameter. In our framework, this variability is captured by allowing Cn2 (0)−and thus the corresponding Cn2 (h) profile−to vary with the satellite’s orbital position, yielding position-dependent blur and a more realistic representation of atmospheric effects. B. Pointing jitter in optical satellite systems In addition to atmospheric effects, high-resolution EO systems are highly sensitive to pointing jitter. In satellite imaging systems, jitter refers to rapid, random time-varying deviations in the orientation of the sensor’s line of sight, typically caused by mechanical vibrations of the platform, attitude control system inaccuracies, residual tracking noise or photoelectric sensor fluctuations. These perturbations lead to angular errors that misalign the beam with respect to its intended direction [11], being particularly relevant in LEO satellites (inter-satellite or satellite-to-ground laser links), where high-resolution imaging demands precise attitude stability to maintain image quality.