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| 2. |
- Speier, Maximilian, et al.
(författare)
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Fundamental Research of Ferrofluids
- 2022
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Ingår i: IAC 2022 Congress Proceedings, 73<sup>rd</sup> International Astronautical Congress (IAC), Paris, France. - : International Astronautical Federation, IAF.
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Konferensbidrag (refereegranskat)
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| 5. |
- Buehler, Stefan A., et al.
(författare)
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ARTS, the atmospheric radiative transfer simulator
- 2005
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 91:1, s. 65-93
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Tidskriftsartikel (refereegranskat)abstract
- RTS is a modular program that simulates atmospheric radiative transfer. The paper describes ARTS version 1.0, which is applicable in the absence of scattering. An overview over all major parts of the model is given: calculation of absorption coefficients, the radiative transfer itself, and the calculation of Jacobians. ARTS can be freely used under a GNU general public license. Unique features of the program are its scalability and modularity, the ability to work with different sources of spectroscopic parameters, the availability of several self-consistent water continuum and line absorption models, and the analytical calculation of Jacobians.
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| 6. |
- Buehler, Stefan, et al.
(författare)
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Recent developments in the line-by-line modeling of outgoing longwave radiation
- 2006
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 98:3, s. 446-457
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Tidskriftsartikel (refereegranskat)abstract
- High frequency resolution radiative transfer model calculations with the Atmospheric Radiative Transfer Simulator (ARTS) were used to simulate the clear-sky outgoing longwave radiative flux (OLR) at the top of the atmosphere. Compared to earlier calculations by Clough and coworkers the model used a spherical atmosphere instead of a plane parallel atmosphere, updated spectroscopic parameters from HITRAN, and updated continuum parameterizations from Mlawer and coworkers. These modifications lead to a reduction in simulated OLR by approximately 4.1%, the largest part, approximately 2.5%, being due to the absence of the plane parallel approximation. As a simple application of the new model, the sensitivity of OLR to changes in humidity, carbon dioxide concentration, and temperature were investigated for different cloud-free atmospheric scenarios. It was found that for the tropical scenario a 20% change in humidity has a larger impact than a doubling of the carbon dioxide concentration. The sensitive altitude region for temperature and humidity changes is the entire free troposphere, including the upper troposphere where humidity data quality is poor.
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| 7. |
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| 8. |
- Delley, Diane, et al.
(författare)
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ASTER: Developing a Platform to Achieve Microgravity for Low-Cost Experiments
- 2021
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Ingår i: IAC 2021 Congress Proceedings, 72nd International Astronautical Congress (IAC), Dubai, United Arab Emirates. - : International Astronautical Federation, IAF.
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Konferensbidrag (refereegranskat)abstract
- Microgravity is an important field of research, which is vital for the efficient future utilisation of space. It is possible to undertake microgravity experiments on-orbit, however, this is often well outside the available funding range of low-cost experiments. Microgravity experiments undertaken on sounding rockets are more accessible to low-budget institutions and students, and provide longer periods of sustained microgravity than drop towers and parabolic flights. However, unless stabilised, such experiments cannot achieve true microgravity conditions due to residual external forces, such as the centrifugal force of the rocket’s spin, acting on the experiment. Thus, projects that want to carry out experiments in microgravity conditions would first need to design the platform required to achieve true microgravity, making these projects more complex and time intensive.Project ASTER (Attitude STabilised free falling ExpeRiment) is designing and testing such a platform for microgravity research. ASTER is taking advantage of the extended microgravity period of a sounding rocket flight to test a high performance, low-cost Attitude Control System (ACS) solution capable of providing microgravity conditions for experiments. This would greatly benefit both future satellite projects and sounding rocket experiments which require highly accurate stabilisation and pointing capabilities. The design utilises three reaction wheels controlled by a closed loop system to stabilise a Free Falling Unit - ejected from a sounding rocket - within seconds. The platform will be able to perform slewing manoeuvres and accommodate future experiments on easily adaptable mounting points which allow for on-board sensors and cameras. ASTER will be launched on-board REXUS 30 in March 2022, after which it will be recovered and the obtained results will be published on an open source basis to ensure its future availability to student and other low budget research projects, thereby allowing further improvement, optimisation, and customisation. ASTER is aiming to establish a platform which simplifies the development of microgravity experiments, especially for student projects which often face tight schedules and limited resources. ASTER is being developed as part of the 13th Cycle of the German-Swedish student programme REXUS/BEXUS by students of Luleå University of Technology (LTU) at the Kiruna Space Campus.
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| 9. |
- Dengel, Ric, et al.
(författare)
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The Low-Cost Attitude Determination and Control System ASTER: Design, Testing and Lessons Learned
- 2022
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Ingår i: IAC 2022 Congress Proceedings, 73rd International Astronautical Congress (IAC). - : International Astronautical Federation, IAF.
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Konferensbidrag (refereegranskat)abstract
- The Attitude Determination and Control System (ADCS) of a spacecraft is often one of the most intricate subsystems, requiring significant resources to develop and integrate. An openly available ADCS platform for sounding rockets can make microgravity experiments more accessible, as development time and cost could be reduced. Project ASTER developed and tested such a solution. The main objective was to develop a low-cost and easy to manufacture system that enables future student teams and scientific missions with limited budget access to an experiment platform with a high-performance ADCS. The design utilises three reaction wheels, controlled by a closed-loop system, to stabilise a Free-Falling Unit ejected from a sounding rocket within seconds. The platform would be able to perform slewing manoeuvres and accommodate future experiments in an easily adaptable payload bay. The design and testing results are being published on an open-source basis allowing further improvement, optimisation, and customisation. ASTER was developed as part of the 13th cycle of the German-Swedish student programme REXUS/BEXUS and is scheduled to fly on REXUS-30 in March 2023. Due to the challenges faced by the project in the last phase of its development, the designed ADCS system will probably not be able to fly as a fully active payload on the REXUS rocket. The module will be assembled during the launch campaign in a reduced configuration and the flight will serve to verify the working systems such as the retention system designed by the team for large Free-Falling Units, as well as the mechanical low-cost design solution of the high-performance reaction wheels. Although the final technical issues encountered by the team during the experiment reviews could not be resolved completely as of now, the verification of the experiment subsystems in flight will be used to validate this initial design and enable further improvements. The project has pushed a team of students to design a very complex experiment and has helped them gain experience in dealing with common issues and failures faced in space projects. The paper will present the lessons learned from the overall project implementation and execution to help future student teams as well as the status of the additional flight opportunity.
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| 10. |
- Earle, M.E., et al.
(författare)
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Volume nucleation rates for homogeneous freezing in supercooled water microdroplets : results from a combined experimental and modelling approach
- 2010
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 10:16, s. 7945-7961
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Tidskriftsartikel (refereegranskat)abstract
- Temperature-dependent volume nucleation rate coefficients for supercooled water droplets, JV(T), are derived from infrared extinction measurements in a cryogenic laminar aerosol flow tube using a microphysical model. The model inverts water and ice aerosol size distributions retrieved from experimental extinction spectra by considering the evolution of a measured initial droplet distribution via homogeneous nucleation and the exchange of vapour-phase water along a well-defined temperature profile. Experiment and model results are reported for supercooled water droplets with mean radii of 1.0, 1.7, and 2.9 μ1/4m. Values of mass accommodation coefficients for evaporation of water droplets and vapour deposition on ice particles are also determined from the model simulations. The coefficient for ice deposition was found to be 0.031 ± 0.001, while that for water evaporation was 0.054 ± 0.012. Results are considered in terms of the applicability of classical nucleation theory to the freezing of micrometre-sized droplets in cirrus clouds, with implications for the parameterization of homogeneous ice nucleation in numerical models.
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