This licentiate thesis considers the combination of multiple instruments for remote sensing of the Earth atmosphere from space. The primary focus is on remote sensing of atmospheric ice. Ice clouds are important for the Earth’s radiation budget, but their properties are difficult to measure and therefore poorly known. A better quantification of ice clouds is needed to improve global climate models. This thesis introduces the reader to the subject and describes how to combine measurements and radiative transfer simulations in an attempt to improve our understanding. A major part of this work is the development of a toolkit to find co-incident measurements, or collocations, between any pair of down-looking satellite sensors. Firstly, this toolkit is used to collocate passive microwave and thermal infrared sensors on meteorological satellites with the Cloud Profiling Radar on CloudSat. With the resulting collocated dataset, the Ice Water Path (IWP) signal in passive thermal radiation is studied and an improved IWP retrieval is presented. The toolkit is also used to better characterise the bias between different copies of passive microwave radiometers on-board polar-orbiting operational satellites. For the Atmospheric Radiative Transfer Simulator (ARTS), version 2, an optimised frequency grid for infrared broadband simulations is shown to be applicable for cloudy simulations. This frequency grid can and will be used to study the IWP signal in thermal infrared radiances. An outlook on a comparison between collocations and simulations is presented in the thesis.

This licentiate thesis is based on two papers which are related to the study ofatmospheric humidity. The first paper mainly focuses on a non linear method forretrieving atmospheric humidity from infrared sounder satellite measurements basedon fuzzy clustering which could potentially improve the retrieval accuracy. The mainaim of this study was to provide a better first guess humidity profile for physicalretrieval algorithms which can further improve retrieval accuracy. This method hasbeen compared against linear and non linear regression retrievals which are the gen-erally used methods to get the first guess profile. The results reveal that the retrievalaccuracy is better for the new method as compared to the conventional methods.Generally, the accuracy of the humidity measurements of radiosonde is poor in theupper troposphere (UT) and is worse for day time measurements due to solar heatingof the humidity sensor. Several methods have been developed to correct the humiditymeasurements of radiosondes in the UT. The second paper presents a detailed analysisof the implications of these corrections and depicts how important they are for satellitevalidation. The corrections have been applied separately for daytime and nighttimeradiosonde measurements and their effects have been quantified by comparing againstthe coinciding satellite measurements in the infrared and microwave spectral rangeused for humidity measurements.

There are special effects in spectroscopy that must be considered in order to fullyexplain how molecular oxygen interacts with radiation in planetary atmospheres.One of these, the Zeeman effect, is described in this thesis. The Zeeman effect is the theory by which energy levels of atoms and molecules are altered by magnetism, and it causes both polarization and line shape to change. The first publication attached to this thesis, Paper I, details the technical and practical implementation of the Zeeman effect in a radiative transfer model. One potential use of magnetically altered spectroscopy is to remotely measure magnetism. Paper II discuss a method for such measurements on weakly magnetized planets by measuring the polarization caused by the Zeeman effect. The article brings up Mars as one potential candidate to utilize the method. To introduce the articles properly, the thesis starts with a shortdescription of the underlying basic theory for radiative transfer and spectroscopy.After the theory chapter, a short description of input necessary to utilize the theory on operational and experimental platforms is presented.

This thesis is composed of three articles, which have the common denominator that they are studies of heating of oxygen ions in the high altitude cusp and mantle in the terrestrial magnetosphere. All data analysis are based on observational data from the Cluster satellites. Oxygen ions originate in the ionosphere, from where they flow up along open cusp field lines. This upflowing ionospheric plasma is generally gravitationally bound and will return as ionospheric downflow. However, if the plasma is sufficiently energized it may overcome gravity and reach the magnetosphere. Further energization is able to put the plasma on trajectories leading downstream along the magnetotail, which may cause the plasma to escape into the magnetosheath. This thesis considers energization of oxygen ions through wave-particle interactions. We show that the average electric spectral densities in the altitude range of 8-15 Earth radii are able to explain the average perpendicular temperatures, using a simple gyroresonance model and 50% of the observed spectral density at the O+ gyrofrequency. We also show that the phase velocities derived from the observed low frequency electric and magnetic fields are consistent with Alfvén waves. Strong heating is sporadic and spatially limited. For three case studies of strong heating, we show that the regions of enhanced wave activity are at least one order of magnitude larger than the gyroradius of the ions, which is a condition for the gyroresonance model to be valid. An analysis indicates that enhanced perpendicular temperatures can be observed over several Earth radii after heating has ceased, suggesting that high perpendicular-to-parallel temperature ratio is not necessarily a sign of local heating. This also explains why we sometimes observe enhanced temperatures and low spectral densities. Three events of very high temperatures and simultaneously observed high spectral densities were studied, and we showed that the temperatures could be explained with the simple gyrofrequency model. We have also provided average diffusion coefficients at different altitudes, which can be used for ion heating and outflow modeling.

Mars is an unmagnetized planet. Mars has no intrinsic magnetic field but has local magnetic anomalies in the crust. The solar wind, which is the plasma flowing from the Sun at supersonic speed, interacts with the magnetic fields of the currents induced in the conductive Martian ionosphere, deviates and slows down to subsonic speeds. A void in the solar wind is formed around the planet as an induced magnetosphere.At the boundary of the induced magnetosphere, the plasma composition changes from being dominated by the major ion in the solar wind (protons) to being dominated by heavy ions of planetary origin. Also, the interplanetary magnetic field, being carried by the solar wind, starts to pile up against the planet to form a magnetic barrier on the dayside, drapes around the planet, stretches due to mass loading, and forms a magnetotail.The gyroradius of a heated proton in the magnetosheath is large in comparison with the size of the induced magnetosphere. Therefore, a fraction of the proton population penetrates the induced magnetosphere boundary, enters the upper layer of the atmosphere (the ionosphere) and subsequently neutralizes at low altitudes. We have conducted a detailed study of an event, in which the magnetosheath protons penetrate the Martian induced magnetosphere boundary (IMB). The spatial extent of the proton precipitation region reached several thousands of kilometers along the orbit of the Mars Express spacecraft.The interaction of the precipitating protons with the Martian atmosphere was modeled using a direct simulation Monte Carlo method. The inclusion of a horizontal magnetic field in the model significantly increased the backscattering of protons compared to the case without a magnetic field. More than 50% of the incoming energy is reflected backwards for a magnetic field of strength 30 nT, compared to 4% in the case of no magnetic field. We have also used hybrid modeling to study the spatial pattern of the precipitation onto the Martian atmosphere both for solar wind protons and protons originating from the planetary atmosphere. The solar wind protons and the exospheric (planetary) protons contribute 60% and 40%, respectively, of the deposition of mass at the exobase for the given input parameters. The precipitating flux decreases substantially at the subsolar point, due to the backscattering of the incoming protons by the more intense piled-up magnetic field.

The powered soft landing of a spacecraft represents a maneuver with high interest, withsome private launcher companies – SpaceX, Blue Origin, Rocket Factory Augsburg, etc. - showinginterest in implementing it as a solution for their launchers, and several national agenciesusing it for the exploration of celestial bodies where it may be the only option. This thesispresents the work done in the theoretical development of a possible control algorithm for thepower landing maneuver of a rocket on Earth’s surface. The first step is the definition of the landingmaneuver based on literature study. This includes the identification of the different phasesof the flight, the selection of control variables, and the establishment of the initial conditionsfor the simulation and the working assumptions. Following this work, the three-dimensionalequations of motion for a rocket-like body are determined and simulated in the absence of anycontrol signal. Two aspects need to be analyzed in the powered landing maneuver: attitudeand velocity control. The second step consists in the implementation of the two respectivealgorithms, which are then applied to the equations system. The newly controlled system isagain simulated, and the results are compared with the ones obtained in the absence of thecontrol. The simulations are expected to provide the position, attitude, and velocity profilesof the rocket both in free fall and with a controlled power-landing. Consequently, the controlsystem is expected to guarantee safe recovery of the spacecraft given different initial conditions.

For transport aeroplanes the Blended-Wing-Body (BWB) configuration shows promise in improving aerodynamic efficiency. The Green Raven project strives to demonstrate hydrogen fuel-cell-electric propulsion on a 4 m wingspan BWB. Due to the lack of a traditional horizontal tailplane, BWBs commonly have multifunctional control surfaces that void assumptions needed for traditional sizing methods. This work endeavoured to produce a control surface configuration that would permit adequate flying qualities of the Green Raven according to the MIL-F-8785C specification, preferably while minimising cruise power draw. The open-source aerospace modelling and optimisation environment SUAVE was chosen for the task, with the intention of adding any needed functionality.SUAVE was modified to permit the definition of general-purpose control surfaces and stability derivatives to be obtained for the additional degrees of freedom they bring which was demonstrated using a SUAVE representation of the Green Raven. The precise procedure for airworthiness-constrained control surface optimisation could not be determined before cessation of work but an outline of a simplified procedure was proposed. / Flygplan med sammansmält vinge och flygkropp (Blended-Wing-Body, BWB) har potential att nå lägre energiförbrukning. På KTH har projektet Green Raven som mål att demonstrera framdrivning med vätgasdrivna bränsleceller på ett obemannat flygplan med denna konfiguration och en spännvidd på 4 m. Då flygplanskonfigurationen BWB saknar konventionell stabilisator är rodren längs vingens bakkant i regel multifunktionella vilket invaliderar beprövade metoder för dimensionering. Detta arbete hade som mål att ta fram en roderkonfiguration till Green Raven-projektet som medger tillfredställande flygegenskaper i enighet med MIL-F-8785C, helst samtidigt som effektbehovet i planflykt minimeras. SUAVE, ett open-source-verktyg för modellering och optimering av flygfarkoster, valdes för uppgiften i vetskap om att vissa kodändringar skulle krävas.SUAVE modifierades för att medge modellering av multifunktionella roder och de extra frihetsgrader de medför vilket demonstrerades genom att ta fram stabilitets- och roderderivator för en modell av Green Raven. En procedur för optimering med krav på flygegenskaper som bivillkor kunde inte färdigställas i tid men en förenklad procedur föreslås.

A reduction in the global use of fossil fuels is necessary when striving for a more sustainable future. One key strategy in the transition from fossil fuels is electrification. This strategy is particularly prominent within the transport sector, where more efficient ways to store electric energy are being pursued. Structural battery composites represent a promising technology. Being based on multifunctional composite materials that can carry mechanical loads and store electrical energy at the same time, they provide a ‘mass-less’ energy storage. This work aims to develop a shape morphing structural battery capable of bending upwards and downwards in a cantilever setup. The structural battery is made from several constituents. Two outer layers of carbon fibers act as negative electrodes and a middle layer of aluminium foil coated with NMC622 on both sides acts as the positive electrodes. Additionally, a glass veil layer and a ceramic separator separate the positive and negative electrodes. A structural battery electrolyte is used to embed the laminate in order to provide load transfer and ion transfer. From this setup, it is possible to control the lithiation/delithiation of each carbon fiber layer independently and thereby bend the laminate in the desired direction. Subsequently, the system is modeled both analytically using Matlab and numerically using Comsol Multiphysics 6.1.  From the models it is found that the system is in theory capable of large deformations, showing promising results. However, the experimental laminates show low capacity upon cycling which would cause near to zero deformations. The poor performance of the system could be linked to incompatibility between the structural battery electrolyte and the NMC622. / En minskning av den globala användningen av fossila bränslen är nödvändig i strävan efter en mer hållbar framtid. En nyckelstrategi i övergången från fossila bränslen är elektrifiering. Denna strategi är särskilt framträdande inom transportsektorn, där effektivare sätt att lagra elektrisk energi eftersträvas. Strukturella batterikompositer representerar en lovande teknik. Genom att vara baserade på multifunktionella kompositmaterial som har förmåga att bära mekaniska belastningar och lagra elektrisk energi samtidigt, ger de en "masslös" energilagring. Detta arbete syftar till att utveckla ett formförändrande strukturellt batteri som kan böjas uppåt och nedåt i en fribärande uppsättning. Det strukturella batteriet är tillverkat av flera beståndsdelar. Två yttre lager av kolfibrer fungerar som negativa elektroder och ett mellanlager av aluminiumfolie belagd med NMC622 på båda sidor fungerar som positiva elektroder. Dessutom separerar ett glasfiberlager och en keramisk separator de positiva och negativa elektroderna. En strukturell batterielektrolyt används för att bädda in laminatet för att ge lastöverföring och jonöverföring. Från denna uppsättning är det möjligt att kontrollera lithieringen/delithieringen av varje kolfiberlager oberoende och därigenom böja laminatet i önskad riktning. Därefter modelleras systemet både analytiskt med Matlab och numeriskt med Comsol Multiphysics 6.1. Från modellerna visar det sig att systemet i teorin är kapabelt till stora deformationer, vilket visar lovande resultat. De experimentella laminaten visar emellertid låg kapacitet vid cykling, vilket skulle orsaka nästan inga deformationer. Systemets dåliga prestanda kan vara kopplat till inkompatibilitet mellan den strukturella batterielektrolyten och NMC622.

Thermal management is a crucial part in the aviation industry. It is also essential that the components involved in aviation be light weight. One of the vital components of thermal management is heat exchangers. It has been observed that the optimization of the heat exchanger is approaching its saturation with traditional manufacturing. To overcome this challenge engineers are exploring the new revolutionary technology of additive manufacturing. Additive manufacturing has created the opportunity of design freedom for the optimization of heat exchangers with complex heat exchanger microchannels and optimized fin designs.This project essentially focuses on generating complex heat exchanger cores with organic lattice structures such as Triply periodic minimal surface (TPMS) geometry. Evaluation of the heat exchanger core has been done using computational fluid dynamic analysis and a comparative study is done to choose the most suitable geometry for the fluid-fluid heat exchangers. A static thermal evaluation of the strut-based lattice structure has been conducted for fin designs and support structure to be used in laser powder bed fusion technology. Additionally, the selected geometry from the analysis has been incorporated into a demonstrator product. The key limitation of this process has been addressed in this project.

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