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Identifying the ideal methanol production plant: Balancing Economic Factors for Green Process Configurations
No full textThe production of liquid energy carriers from agricultural waste materials like bark or straw could significantly aid in the defossilization of the chemical industry. To evaluate their potential contribution correctly, it is necessary to define process designs dependent on site-specific boundary conditions due to the variability of local biomass supplies, heat markets and availability of renewable power. Although biomass-based pathways have the advantage of being more mature, the addition of renewably-generated hydrogen offers the chance to greatly boost the degree of carbon use.
The proposed methodology for evaluating the potential of a biomass-to-liquid concept incorporates economic constraints into the process design, allowing for the identification of regionally adjusted process designs. A detailed flowsheet simulation of the concept is set up in AspenPlus® based on validated experimental data (Frilund, 2021). An in-house software tool, TEPET (Techno-Economic Process Evaluation Tool), has been extended by an automated utility integration to identify "sweet spots" within Europe (Maier, 2021).
The conducted evaluation includes two different feedstocks, three different process configurations, including the integration of hydrogen produced through renewable sources, and multiple heat utilization modes. For each region, the most advantageous process design is defined and depicted. Additionally, a correlation between economic boundary conditions such as the electricity and heat market, and the process design will be presented.
The proposed methodology and simulation tools provide a comprehensive evaluation of the potential of this concept, taking into account economic and regional factors. The study also highlights the importance of incorporating renewably-generated hydrogen and heat utilization modes in the process design to increase the extent of carbon utilization. Overall, the results of this study demonstrate the potential for biomass-to-liquid processes to make a significant contribution to a sustainable transition
Combining several Simulation Paradigms to Evaluate and Visualise Airport and Aircraft Operations
No full textAgriROSE-L 2025 Case Study: Soil Moisture Estimation from L-Band PolSAR Time Series
No full textRecently, the German Aerospace Center (DLR) conducted the AgriROSE-L 2025 (CROPEX 2025) airborne F-SAR campaign in preparation for the upcoming ESA ROSE-L mission. Multiple flights acquired a long and dense (6-day revisit) time series of fully polarimetric SAR acquisitions over agricultural areas between April and July 2025. Ground teams accompanied each flight to collect in situ measurements and record the soil and vegetation conditions. Agricultural areas are subject to rapid changes caused by crop growth, transitions of phenological stages, and alterations in soil conditions, including changes in soil moisture and roughness. The campaign provides a valuable dataset for analyzing the dynamics of the polarimetric signal over time and developing new methods for geophysical parameter retrieval.
In this study, we provide an early evaluation of the new dataset, focusing on soil moisture estimation, an essential climate variable (ECV) important for hydrology and agriculture. A significant challenge for SAR-based high-resolution soil moisture estimation is the presence of vegetation, which interferes with the ground signal. Here, the use of longer wavelengths (L-band) with deeper penetration is beneficial in minimizing the influence of vegetation. Additionally, using fully polarimetric data enables a certain degree of separation between the ground and vegetation contributions.
We apply a model-based tensor decomposition [1] to separate the signal into surface, dihedral, and volume contributions. The method jointly exploits polarimetric and temporal information, analyzes a time series of acquisitions, and provides estimates for different geophysical parameters, including soil moisture. We validate the accuracy across different crop types and growth stages using the in situ measurements acquired during the campaign.
References
[1] N. Basargin, A. Alonso-González, and I. Hajnsek, "Model-based tensor decompositions for geophysical parameter retrieval from multidimensional SAR data," Submitted to IEEE Transactions on Geoscience and Remote Sensing, under review
A Review of Orthogonal Waveforms for Spaceborne Multiple-Input Multiple-Output Synthetic Aperture Radar
No full textSpaceborne Multiple-Input Multiple-Output Synthetic Aperture Radar (MIMO-SAR) overcomes fundamental shortcomings of state-of-the-art SAR, such as the trade-off between swath width and spatial resolution, and offers a greater agility of the antenna beam steering. In addition, MIMO-SAR enables a wide variety of new operation and acquisition modes, such as the High-Resolution Wide-Swath (HRWS) mode. One demanding requirement in this subject is to design separable orthogonal waveforms which optimize the overall imaging performance. In the case of a SAR system, this is not an easy task due to the nature of the imaged scene consisting of a multitude of point and distributed targets. This paper summarizes the most promising waveforms in the literature and analyzes them in detail. The selected waveforms are investigated for the first time with respect to their use in SAR using the ambiguity function. As a conclusion, a catalogue of important waveform performance parameters and an ambiguity function analysis are provided, to support the modern MIMO-SAR designer in the form of decision rules for the optimal waveform selection
TWIST-NZ - Tree Water and Soil Moisture Integration for Satellite Calibration and Validation in New Zealand - Early BIOMASS results
No full textThe ESA BIOMASS mission aims to retrieve above-ground biomass and forest height data to enhance our knowledge about the state of the Earth’s forests and the carbon cycle. Besides these
primary mission parameters, its P-band (430 MHz) SAR sensor is also able to provide information on secondary geophysical variables, such as tree trunk water content (TWC) and
upper root-zone soil moisture (RZSM). These parameters are essential for understanding the Earth’s climate and vegetation-hydrology interactions, and play an essential role in the soilplant-atmosphere feedback processes [1,2]. However, they remain insufficiently validated in current global Earth Observation frameworks. The TWIST-NZ project seeks to establish a framework to validate secondary mission products
at three sites in New Zealand. New Zealand offers a unique environment with varying climatic zones, soil types, and geology with the same dominant tree species, Pinus radiata (D. Don) [3],
making it an ideal location for testing satellite-derived estimates of TWC and RZSM based on P-band BIOMASS observations. Additionally, during the Forest Flows program (2019-2025)
research sites were intensely measured with a series of integrated terrestrial and remote sensing measurements [4], including airborne P-Band SAR [5]. We will take advantage of the
established sensor networks and previous measurements to evaluate the sensitivity of the Pband radar sensor to RZSM, assess the seasonality in TWC, and examine the variability in
RZSM across three different forest with contrasting climate, geology and soil. For the estimation of TWC and SM from P-band BIOMASS data, the approaches from [1,2,6]
should be adapted and further refined. These approaches include polarimetric decomposition of SAR observations as well as signal modeling based on physically-constrained methods (such
as the multi-layer soil scattering and radar vegetation interaction models). For the validation of the secondary products, in situ measurements from the Forest Flows monitoring network
(https://www.forestflows.nz), acquired airborne P-band SAR observations from the SlimSAR system (aligning with BIOMASS satellite overpasses to ensure comparable environmental
conditions), and satellite observations (e.g., NiSAR) should be employed and integrated in a multi-scale observation framework.
By validating these secondary products, TWIST-NZ aims to enhance the scientific reliability and extend the practical relevance of BIOMASS for ecosystem monitoring, hydrological
modeling, and forest management. Further, all processed datasets, validation results, and analysis methods will be made publicly available, e.g., via the ESA Multi-Mission Algorithm
and Analysis Platform (MAAP).
[1] Fluhrer, A., T. Jagdhuber, A. Tabatabaeenejad, H. Alemohammad, C. Montzka, P. Friedl, E. Forootan, and H. Kunstmann (2022): Remote sensing of complex permittivity and penetration depth of soils using P-band SAR
polarimetry. Remote Sensing 14(12), 2755. DOI:10.3390/rs14122755
[2] Fluhrer, A., T. Jagdhuber, C. Montzka, M. Schumacher, H. Alemohammad, A. Tabatabaeenejad, H. Kunstmann, and D. Entekhabi (2024): Soil Moisture Profile Estimation by Combining P-band SAR Polarimetry with
Hydrological and Multi-Layer Scattering Models. Remote Sensing of Environment 305, 114067. DOI:10.1016/j.rse.2024.114067
[3] Zhu, H., Meason, D.F., Salekin, S., Hu, W., Lad, P., Jing, Y. and J. Xue (2024). Time stability of soil volumetric water content and its optimal sampling design in contrasting forest catchments. Journal of Hydrology 131344;
DOI:10.1016/j.jhydrol.2024.131344
[4] Meason, D.F., Matson, A., Baillie, B., Moller, D., Dudley, B., Srinivasan, M.S., Rajanayaka, C., Zammit, C., and D. White (2021): Forest Flows – Real time monitoring of water quantity and quality spatio-temporal
dynamics in planted forests. IGARSS 2020 - 2020 IEEE International Geoscience and Remote Sensing Symposium, Waikoloa, HI, USA, 2020: 4626-4629; DOI:10.1109/IGARSS39084.2020.9324637
[5] Zhao, Y. -H., Moller, D., Meason, D., and M. Moghaddam (2024). Multifrequency Subsurface Soil Moisture Retrieval for Forest Flows: A Case Study in Te Hiku, New Zealand. IEEE Journal of Selected Topics in Applied
Earth Observations and Remote Sensing; DOI:10.1109/JSTARS.2024.3493118
[6] Fluhrer, A., H. Alemohammad, and T. Jagdhuber (2025): Analyzing the dihedral scattering component of Pband SAR signals for trunk permittivity estimation–a concept study. Science of Remote Sensing 11, 100236.
DOI:10.1016/j.srs.2025.10023
Limits of Soil Moisture Retrieval at L-Band over Bare and Vegetated Fields using Airborne Polarimetric D-InSAR
No full textObserving changes in soil moisture with differential Synthetic Aperture Radar (SAR) interferometry (D-InSAR) has gained relevance due to shorter satellite revisit times, bigger swath widths, higher spatial resolution of SAR systems, and the introduction of L-band satellites. The geometric configuration of D-InSAR mitigates topographic effects, baseline-induced distortions, and geometric decorrelation.
In this context, the separation of volume, surface and dihedral scattering in the SAR signal is essential for limiting uncertainty in the accurate estimation of soil moisture. Using D-InSAR recent soil moisture forward models are able to account for varying soil states and surface and subsurface volume scattering combinations, although they assume the absence of topographical variations and vegetation between acquisitions [1], [2]. Whereas former can be approximately removed by using phase triplets, separating above ground volume from surface scattering remains a challenge. To address this, polarimetric information has been shown to be sensitive to vegetation [3].
To enhance soil moisture estimation we combine existing D-InSAR electromagnetic forward models with polarimetric information. Here, the copolar phase differences (CPD) [4] can been used to counteract the need of auxiliary geometries and fully-polarimetric systems. CPD has been shown to be highly sensitive to volume scattering due to the structural anisotropy of vegetation.
This analysis will focus on quantifying the performance of Zwieback et al. [2] at L-Band and HH/VV polarizations by deploying it on the recent AgriROSE-L dataset [5]. The limits of the model will be explored in respect to its parameterization, the degree of vegetation and numerous soil moisture levels. First, we test the model performance over bare ground. Secondly, we analyze the value of CPD for identifying vegetated and non-vegetated pixels. Third, we provide a first approach of integrating a CPD indicator into current soil moisture forward models.
References
[1] F. De Zan, A. Parizzi, P. Prats-Iraola, and P. López-Dekker, “A SAR interferometric model for soil moisture,” IEEE Transactions on Geoscience and Remote Sensing, 2013.
[2] S. Zwieback, S. Hensley, and I. Hajnsek, “A polarimetric first-order model of soil moisture effects on the DInSAR coherence,” Remote Sensing, vol. 7, no. 6, pp. 7571–7596, 2015.
[3] G. Anconitano, M. Lavalle, M. A. Acuña, and N. Pierdicca, “Sensitivity of polarimetric SAR decompositions to soil moisture and vegetation over three agricultural sites across a latitudinal gradient,” IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 17, pp. 3615–3634, 2023.
[4] V. Brancato and I. Hajnsek, “Analyzing the influence of wet biomass changes in polarimetric differential SAR interferometry at L-band,” IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 11, no. 5, pp. 1494–1508, 2018.
[5] H. I. Schauer, N. Basargin, and I. Hajnsek, “Airborne L-Band soil moisture retrieval over agricultural areas in preparation for ESA ROSE-L mission,” 2025
Synthetic study of ionosphere lower boundary forcing using TIE-GCM
No full textIn this study, we use the general circulation model TIE-GCM as well as different synthetic lower boundary forcing conditions to �investigate the behavior of the lower Thermosphere Ionosphere (TI) system. The lower boundary forcing is synthetically generated to artificially mimic different atmospheric conditions and then used as input for TIE-GCM. The influence of these conditions on the TI system will be analyzed by investigating different thermosphere as well as ionosphere parameters. The goal of this study is to improve the understanding of the importance of the different (internal vs. external) driving mechanisms in the TI system
Observer based Control for Railway Vehicles with Driven Independently Rotating Wheels Front-Rear Comparison on a 1:5 Scale Test Rig
No full textDriven Independently Rotating Wheels offer significant performance benefits, but achieving stable and effective control requires
accurate estimation of lateral displacement of the wheel carrier. This
paper presents a simple, tunable two-step observer that addresses this
challenge, integrated with a cascaded PI-PD control system for enhanced
performance. Additionally, we examine the distinct stability conditions of
the front and rear wheel carriers and demonstrate how these differences
affect both observer and controller design. The proposed approach is validated on a 1:5 prototype developed by the German Aerospace Center
(DLR), showcasing its effectiveness in real-world applications
EPOS-Lid: Lidar benchmark dataset for pose estimation during non-cooperative rendezvous
No full textLidar sensors are increasingly studied for space rendezvous applications, in particular for on-orbit servicing or active debris removal missions. With their active measurement principle, they provide accurate 3D point clouds which enable precise pose estimation. While simulated lidar data is relatively simple to generate under ideal conditions, real lidar point clouds can present high levels of noise and reflections. There is the need for representative lidar data to train and test pose estimation methods for non-cooperative space rendezvous scenarios. This work introduces EPOS-Lid, an openly available lidar benchmark dataset for this task. It comprises a synthetic dataset for training pose estimation methods, and real lidar point clouds collected at the European Proximity Operations Simulator (EPOS). Further, it is demonstrated with evaluation of benchmark methods how the datasets can be used for training and testing pose initialization and pose tracking methods
Investigation of turbulent wedge intermittency with time-resolved temperature-sensitive paint
No full textTurbulent wedges and turbulent spots play a significant role in the process of laminar-turbulent transition. In most cases, turbulent wedges are quasi-stationary in the sense that their core is fully turbulent, bounded by an intermittent region. For some flow conditions, however, intermittent turbulent wedges occur characterized by reduced intermittency values and heat transfer rates compared to classical, fully turbulent wedges. They were first described by Clark et al. in a low-speed flow and termed transitional wedge.
In this study, turbulent wedges and turbulent spots were investigated experimentally at large Reynolds numbers (local Reynolds numbers up to Re_x=5.2*10^6), Mach numbers M from 0.5 to 0.8 and various stream-wise pressure gradients in the Cryogenic Ludwieg-Tube of DLR Göttingen. The examined wind-tunnel model was the two-dimensional flat plate "PaLASTra", which was designed to have a large area of uniform pressure gradient on the surface of interest - the upper side of the model. Time-resolved temperature-sensitive paint enabled the determination of global temperature measurements at camera frame rates of 20 kHz, which were further evaluated to obtain instantaneous heat-flux distributions and intermittency maps. These were used to quantitatively analyze turbulent wedges and turbulent spots. For the case of fully turbulent wedges, the intermittent region bounding the turbulent core was quantified for the first time using a thermographic measurement technique at these conditions.
The spreading angle of the intermittent region (10.02 +- 0.09°) was found to be similar to those of individual turbulent spots (10.2+-0.4°), demonstrating the similarity of the mechanism of spanwise growth for turbulent wedges and turbulent spots.
Additionally an intermittent turbulent wedge was identified. By determining the time-resolved heat flux distribution, it was possible to demonstrate that intermittent turbulent wedges comprise individual turbulent spots. Due to the growth of turbulent spots in both spanwise and streamwise direction, the intermittency values were found to increase in the downstream direction. Furthermore it was possible to detect the merging of individual turbulent spot. Detailed results of the time-resolved heat-flux and intermittency distribution of the turbulent wedges will be provided in the final contribution