master thesis proposalsfor this master thesis project, the student will have to reduce and analyze...
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Master Thesis Proposals
2020-2021
Space Sciences
Faculty of SciencesLiège University
Important notice!
The present catalogue is especially relevant for master theses in the Research focus.Its content is not exhaustive, and students are encouraged to contact specific teachers/researchers toask them about potential alternatives if they are interested in other topics.
For the Professional focus, the master thesis must be an internship and there is no specific offerprepared in advance. Students are encouraged to search for opportunities out of the AGODepartment. To do so, contacting other institutes is highly recommended, including
- Liège Space Centre (Sart-Tilman) : http://www.csl.uliege.be (or via S. Habraken, C. Barbier, J.Loicq)- Belgian Institute for Space Aeronomy (Brussels) : http://www.aeronomie.be/en/- Royal Observatory of Belgium (Brussels) : https://www.astro.oma.be/en/- Royal Institute for Meteorology (Brussels) : https://www.meteo.be/en/- The AMOS company (Sart-Tilman) : https://www.amos.be/- The Aerospacelab company (Mont-Saint-Guibert): https://www.aerospacelab.be/
… or any other company involved in space activities.
About master theses out of ULiège...
Students involved in internships (abroad, in Belgium, and even at the Centre Spatial de Liège) haveto fill in an internship agreement and a risk analysis sheet. These documents must be completed inconcertation with the person responsible for the internship at the host institution, with the agreementof the teacher/academic supervisor in ULiège.
Link to the required documents :https://www.enseignement.uliege.be/cms/c_9413472/en/etape-4-fiche-d-analyse-de-risque-et-convention
For any question or request for assistance, the contact person for the Faculty of Sciences is MrsKristel Karremans: [email protected]
In addition, for a stay abroad it is mandatory to follow an on-line procedure to officially request theauthorization to the Rector of the University. This is necessary for the validation of the activityabroad in the student programme and for benefiting of an insurance coverage. The request should beintroduced at least one month (sooner is better!) before the expected date of departure.
Astroparticles, Dark matter and Gravitational waves
Contact person : J.R. Cudell
e-mail : [email protected]
Tel : 04 366 3654
Office: 4/44 (B5a)
Availability: most afternoons in May or June. Check via e-mail if you want to be sure,
Thematics : Cosmology and astropaticles
Description:
A number of possibilities exist (in particle physics, astroparticle physics, dark matter, gravitationalwaves,…), and I encourage interested students to come and see me.
Integral field spectroscopy study of a gravitationally lensed quasar
Contact person: Dominique Sluse
e-mail : [email protected]
Tel : 043669797
Office: B5c, +1/10
Availability: Interested students should contact me by e-mail to find the best time for an appoint-ment.
Thematics: Observational Extragalactic Astrophysics
Description:
Gravitationally lensed quasars are used for a variety of astrophysical applications: measurement of the expansion rate of the Universe, micro-lensing based estimate of the size of the accretion disc around supermassive black holes, study of the dark matter content of galaxies, … For this master thesis project, the student will have to reduce and analyze integral field spectroscopydata of one gravitationally lensed quasar. The data, obtained with the MUSE integral field spectro-graph mounted on one of the Very Large Telescopes of the European Southern Observatory in Paranal, will be used for one of the following projects (depending of skills and interest of the stu-dent) required for turning gravitationally lensed quasars into accurate cosmological probes, namely:
Identify automatically galaxies in the field of view of the lens system and measure their red-shifts (interactively or automatically).
Measure the velocity dispersion and stellar mass of the lensing galaxy and/or of field galax-ies, and quantify systematic errors affecting those measurements.
Characterize the presence and amplitude of microlensing in the images of the lensed quasar.
Alternative projects in the field of extragalactic astrophysics are possible. Students are encouraged to contact me to discuss of other opportunities.
Having attended the classes on Extragalactic astrophysics (SPAT0011) and Programming techniquesand numerical methods (SPAT0002) is strongly recommended.
The impact of atmospheric eclipses on the light curves of close massivebinaries
Contact person : Gregor Rauw, High-Energy Astrophysics Group
e-mail : [email protected]
Tel : 04/366 9740
Office: B5c, 2/2
Availability: 5 & 12 May between 14h00 and 17h00. Interested students should ideally contact meby e-mail to arrange an alternative appointment if needed.
Thematics : Stellar astrophysics
Description:
The vast majority of massive stars reside in binary or higher multiplicity systems. Eclipsing binariesare especially important as they allow to infer the fundamental properties (masses and radii) of thestars. The overwhelming majority of the studies of such systems assume that the stars are opaqueand that their shapes can be described by the Roche potential. However, massive stars feature dense,partially optically thick stellar winds. In close binary systems, these winds can absorb some of thelight of the companion, producing a so-called atmospheric eclipse and leading to situations wherethe surface corresponding to optical depth unity (τ=1) lies beyond the Roche lobe. Both effects(atmospheric eclipse and R(τ=1) larger than the radius of the Roche lobe) are not accounted for inthe codes based on the Roche model. The goal of this project is to implement a numerical code forthe calculation of light curves of close binaries which accounts for the shape of the stars (based onthe Roche potential), the mutual eclipses of the opaque stellar surfaces and the atmospheric eclipsesand to compare the results with existing data.
Photometric and spectroscopic studies of an Algol binary
Contact person : Gregor Rauw, High-Energy Astrophysics Group
e-mail : [email protected]
Tel : 04/366 9740
Office: B5c, 2/2
Availability: 5 & 12 May between 14h00 and 17h00. Interested students should ideally contact meby e-mail to arrange an alternative appointment if needed.
Thematics: Stellar astrophysics
Description:
Algol-type binaries are systems where a cool evolved star is overflowing its Roche lobe and istransferring material to a B-type main sequence companion. This mass-transfer process episodicallyleads to the formation of an accretion disk around the mass gainer. We propose here an in-depthstudy of such an Algol binary where we combine photometric and spectroscopic observations tospecify the fundamental parameters of the stars. The student is asked to• get acquainted with the subject of Algol-type binaries, and with the existing literature on thetarget of the study,• process and normalize the spectroscopic observations of the system that have been collectedby our team,• perform the spectral disentangling of the series of spectroscopic observations and classifythe components of the system,• based on the results of the previous point, analyse the photometric lightcurve of the systemand establish the error bars on the inferred parameters,• perform a Doppler tomography of the Hα line in order to search for signatures of anaccretion disk or other accretion structures,• summarize the results, compare them with the literature and discuss their implications.
Assessing the probing potential of mixed modes in Red Giants
Contact person : Charly Pinçon, Marc-Antoine Dupret
e-mail : [email protected], [email protected]
Tel : 04 366 9721 (CP), 04 366 97 32 (MAD) (after the confinement)
Office: B5c +1/1 or +1/12
Availability: From May through videoconf
Thematics : Astrophysics: Stellar physics, Asteroseismology
Description:
Once their central hydrogen is exhausted, low-mass stars leave the main sequence and startevolving on the red giant branch. At this evolutionary stage, stars are composed of a small-sizedhelium core in contraction located below a thin hydrogen-burning shell, all surrounded by a dilutedexpanding envelope. Due to their core-envelope structure, red giant stars exhibit a peculiar kind ofstochastically-excited oscillations called mixed modes. These modes can propagate in the centralradiative region, where they behave as gravity modes, and in the convective envelope, where theybehave as acoustic modes. Unlike pure acoustic modes in main-sequence stars, the frequencypattern of mixed modes in red giant stars thus gives us the unique opportunity of probing theproperties not only of their outer envelope, but also of their inner layers.
Theoretical analyses of mixed modes demonstrate that their frequency pattern depends on four mainparameters. Due to the high-quality seismic data provided by the CoRoT and Kepler satellites, theseindicators have already been measured in thousands of evolved stars and have already given usstringent constraints, for instance, on the contraction state of their helium cores. Nevertheless, therelation existing between these four indicators and the internal properties of red giant stars needs tobe further scrutinized in order to fully exploit their ability of constraining not only theirevolutionary state, but also their whole evolution in general. Indeed, the structure of red giant starsmay conserve the signature of past events and may also supply the initial conditions for themodeling of later phases such as white dwarfs. Moreover, due to their high luminosity and theirwide range of mass, red giant stars represent key targets for Galactic archaeology.
In this context, the aim of this project will be to assess the link between the seismic parametersassociated with mixed modes and the stellar internal properties. The work of the student will consistin determining the considered seismic indicators throughout a grid of stellar models and in studyingtheir dependence with the stellar parameters such as the age, the mass, the metallicity, the mixing-length, the efficiency of the convective boundary mixing, as well as in understanding the physicalorigins of the observed trends. To do so, the student will use the stellar evolution code CLEScoupled with the oscillation code LOSC that are developed in the team ASTA. The results of theinvestigation will be compared to the current large-scale observations and discussed accordingly.This subject is ideal for a student interested in stellar evolution and stellar oscillations, with basicanalytical and programming skills.
Recommended courses: Stellar structure and evolution I SPAT0044-1 (& II SPAT0045-1) & Stellarstability and asteroseismology SPAT0005-1 (Pr. M-A Dupret)
Helium glitch analysis in solar-like stars
Contact person: Marc-Antoine Dupret, Martin Farnir
e-mail: [email protected], [email protected]
Tel: 04 366 9721 / 9732 (after the confinement)
Office: B5c +1/1 or +1/12
Availability: From May by videoconf
Thematics: Astrophysics: Stellar physics, Asteroseismology
Description:
As the search for habitable exoplanets goes on, our attention is drawn towards solar-like stars.Thanks to space missions such as Kepler, a wealth of data of unprecedented quality has yet to beanalysed. With such data, it becomes essential to exploit as much of the available information aspossible, and to do so in a reliable and accurate way. Solar-like stars are cool low mass starsexhibiting p-type stellar pulsations excited by stochastic mechanisms. Aside from the regularpattern observed in the oscillation spectrum (e.g. large and small separations) a very low amplitudeoscillating signal may be observed in the frequencies. This is the glitch which is caused by a sharpvariation in the stellar structure. The analysis of such a signal may then provide an inference on thesurface helium abundance, which is inaccessible by other means in these cool stars.
The aim of the thesis will be to study several targets from the Kepler LEGACY sample, whichrepresents the best data at disposal for asteroseismology of solar-like stars, to provide a preciseestimation of their fundamental parameters (mass, composition, age, etc). The exceptionnal qualityof the Kepler LEGACY data enables us to retrieve the faint signature of glitches. However, this alsocalls for very accurate oscillation spectrum analysis techniques. Appropriate tools have beendeveloped in the ASTA team such as the CLES stellar evolution code, LOSC oscillation code andthe WhoSGlAd method for the oscillation spectrum and glitches analysis. The best fit stellar modelsearch will combine these tools with a minimisation algorithm. The project may take severaldirections according to the student’s intents. Several solar-like targets may be treated (e.g. Sun as astar data, binaries or peculiar stars) but more theoretical work may be done also such as theexploration of the helium glitch signature, and associated seismic indicators, throughout the HRdiagram based on a grid of theoretical models. This project is well suited for a student that iscurious about the physics of stellar models and who has basic programming knowledge.
Recommended courses: Stellar structure and evolution I SPAT0044-1 (& II SPAT0045-1) & Stellarstability and asteroseismology SPAT0005-1 (Pr. M-A Dupret)
Modeling the Shear Layer Oscillation and its impact on the rotation of low-mass stars
Contact person : Charly Pinçon, Marc-Antoine Dupret
e-mail : [email protected], [email protected]
Tel : 04 366 9721 / 04 366 97 32 (after the confinement)
Office: B5c +1/1 or +1/12
Availability: From May by videoconf
Thematics : Astrophysics: Stellar physics, Hydrodynamics, Rotation, Waves
Description:
Rotation is an important ingredient of the stellar structure. For example, it can induce transport ofchemical elements that is able to refresh nuclear burning cores with hydrogen and thus to increasethe star lifetime on the main sequence. However, current seismic observations show that the centralrotation of low-mass stars during evolution from the main-sequence to helium core burning stagesand even to white dwarfs, is lower than expected from the current stellar evolution codes. Anefficient mechanism therefore needs to be included in stellar models in order to reproduce theseobservations. Among different possibilities, internal gravity waves remain a serious candidate.
Internal gravity waves are excited by turbulent motions in the convective region and can propagatein the underlying radiative region. During their travel throughout the radiatve core, these wavessuffer radiative losses so that they can deposit a part of the angular momentum into the medium andthus locally modify the rotation rate. In particular, previous works showed that they drive a small-scale oscillation of the rotation profile in a thin layer just below the base of the convective regionwith a typical period of the order of the year, the so-called Shear Layer Oscillation (SLO). This isequivalent to the Quasi-Biennal Oscillation (QBO) observed in the terrestrial atmosphere. The SLOfilters the wave energy flux transmitted towards the center of the star and thus can have an impacton the efficiency of the wave-induced core acceleration. Nevertheless, it is difficult to take thiseffect into account in stellar modeling since it deals with timescales much smaller than the typicaltimescale of stellar evolution.
The aim of this master project is to quantify the impact of the SLO on the wave-induced angularmomentum transport through a simplified modeling. The work will consist in numerically solvingthe differential equations of the evolution of the mean flow in a thin layer just below the convectiveregion and exploring the associated parameters space. The initial configuration of the model will beone-dimensional, plane-parallel, with a constant stratification, and will consider only the effects ofmonochromatic waves and a constant turbulent diffusivity. Improvements in the modeling could beenvisaged given the advancement of the project. The final goal will be to propose simpleprescriptions that can be easily included in stellar evolution codes. This project is well suited forstudents interested in solving general physical problems and especially hydrodynamics, with goodanalytical and numerical skills.
Recommended courses: Stellar structure and evolution I SPAT0044-1 & II SPAT0045-1 (Pr. M-ADupret)
Seismic probing of γ Dor stars observed by Kepler
Contact person : Marc-Antoine Dupret, Sébastien Salmon
e-mail : [email protected]
Tel : +32 4366 9732 (after the confinement)
Office: B5c, room 1/12
Availability: From May by videoconf.
Thematics : Astrophysics: stellar physics, asteroseismology
Description:
Gamma Doradus stars are main-sequence A and F-type stars presenting high-order gravity modes ofpulsations. Some of them present an hybrid-pulsator character by also showing pressure modes,known as δ Scuti variability. For a while, their pulsations were hardly detectable from ground-based observatories. Yet, the Kepler space telescope, with its long and uninterrupted observingcampaigns, revealed rich and complex stellar pulsation spectra in hundreds of γ Dor stars. Since alarge fraction of these stars are moderate to fast rotators, the analysis of their pulsations hasrevealed a huge potential for characterising their internal rotation profile and thus internal transportprocesses of chemical species and angular momentum. In particular, recent studies reporteddetection of rotational signatures both in their gravity and pressure frequency spectra of oscillations.Furthermore, convincing evidence of the detection of Rossby waves was reported. These gravito-inertial waves only appear with rotation as Coriolis force acts as part of their restoring force. Theimprint of rotation and chemical stratification in oscillations paves the way for probing them inthese stars.
Within the ASTA team, we are developing for many years numerical tools allowing us to modelstars from their structure to the computation of their pulsations. With help of these unique tools, thestudent will analyse and do the detailed modelling of some of the most promising hybrid γ Dorstars detected by Kepler. He/she will focus on the constraints that these stars can bring on theinternal stellar rotation, chemical composition and the link with their past stellar evolution.
Recommended courses: Stellar structure and evolution I SPAT0044-1 (& II SPAT0045-1) & Stellarstability and asteroseismology SPAT0005-1 (Pr. M-A Dupret)
Revisiting the instability strips of sdB stars
Contact person : Valérie Van Grootel & Marc-Antoine Dupret
e-mail : [email protected] ; [email protected]
Tel : +32 4366 9730/9732
Office: B5c, room 1/13 or 1/12
Availability: By email.
Thematics : Astrophysics: stellar physics, asteroseismology
Description:
The stars studied in this master project are extreme horizontal branch stars, also known as subdwarfB (sdB) stars. They represent an advanced stage of stellar evolution, after the main sequence wherethe stars spend most of their lives and after the first red giant phase. These hot (Teff=20,000-40,000K) and compact (log g=5.2-6.2) objects burn helium in their cores into carbon and oxygen and aresurrounded by an extremely thin H-rich envelope. Understanding the formation of sdB stars is oneof last big mysteries of stellar evolution. Some sdB stars present pulsations, which open the possi-bility to apply asteroseismology (the study of stellar pulsations) to model these stars.
The proposed master thesis concerns the instability strip of sdB stars: we aim to determine when(i.e. at which masses, effective temperature and surface gravity) these stars present excited pulsationmodes and when they are not predicted to pulsate. Three groups of sdB pulsators are known: theshort-period (80-500 sec) sdB pulsators with temperatures Teff around 34,000K which were the firstto be discovered; the long-period (1-3h) sdB pulsators with cooler Teff around 28,000 K and lowersurface gravities; and finally very hot (50,000-60,000 K) and very compact post-sdB pulsators withvery short periods (less than one minute), recently found. Our classical models of sdB starscorrectly predict and reproduce the properties of the pulsations of the first group (the short-periodpulsators), but not at all those of the second (long-period) and third (very hot) group. The culprit isidentified since a couple of years: the absence of Ni in our sdB models. Unfortunately, no trustableopacity tables for Ni were available to us until very recently. This is now the case, and new sdBmodels including Ni have now been built.
The aim of this Master thesis is to revisit the instability strips of the three groups of sdB pulsatorswith these new sdB models. The goal is to determine if we can still correctly reproduce thepulsation properties of the first group of sdB pulsators, and if we can better reproduce the observedinstability strips of the second and the third groups with these new models. The non-adiabatic MADpulsation code (developed by Pr. Marc-Antoine Dupret) will be used to pulsate the sdB models. Inparticular, the MAD code includes various prescriptions for the interaction between pulsations andconvection, a potentially important effect to account for pulsations in sdB stars, but that has neverbeen tested.
Recommended courses: SPAT0005-1 Stellar Stability and asteroseismology, SPAT0045-1 Stellarstructure and evolution II (Pr. M.A. Dupret)
Modeling TESS data of extreme horizontal branch stars byasteroseismology
Contact person: Valérie Van Grootel
e-mail: [email protected]
Tel: +32 4366 9730
Office: B5c, room 1/13
Availability: Any time by email.
Thematics: Astrophysics: stellar physics, asteroseismology
Description:
The TESS satellite from NASA gathers since December 2018 high-quality photometric data on var-ious stars, for searching transiting exoplanets but also for asteroseismology. Asteroseismology is thestudy of stellar oscillations in order to tightly constrain the physics inside stars and hence, to refinethe models of the structure and the evolution of stars.
Among these stars, TESS observes each month (one Sector of the sky each 27 days) dozens of ex-treme horizontal branch stars, and discovers/confirms pulsations in a few of them. Extreme horizon-tal branch stars, also known as subdwarf B (sdB) stars, represent an advanced stage of stellar evolu-tion. These hot (Teff=20,000-40,000 K) and compact (log g=5.2-6.2) objects burn helium in theircores into carbon and oxygen and are surrounded by an extremely thin H-rich envelope. Under-standing the formation of sdB stars is one of last big mysteries of stellar evolution.
The proposed master thesis concerns the asteroseismic modeling of sdB stars observed by TESS.First step will consist in selecting the most promising targets for asteroseismic modeling: presenceof a rich pulsation spectrum, availability of good spectroscopic constraints. The second step is pre-liminary asteroseismic analyses on the most promising targets, in order to select one that will bestudied in depth during this master thesis in the third step. The asteroseismic modeling consists inquantitatively comparing the computed oscillation periods for large sets of stellar models to the ob-served periods. By optimizing this comparison (through genetic algorithms that have been devel-oped for this purpose) to find the best-fitting model to the observations, the seismic modeling willyield the global parameters (e.g. stellar mass and radius) and internal structure and composition(e.g. envelope layering, core composition) of the star. Results will then be exploited, by comparingthem to those of other sdB stars modeled by asteroseismology and by interpreting them in a contextof sdB formation. All the tools are available and ready for a direct application to these TESS data.
This subject is well-suited for a student who like to work on concrete applications of asteroseismol-ogy and space-based observations.
Recommended courses: SPAT0005-1 Stellar Stability and asteroseismology, SPAT0045-1 Stellarstructure and evolution II (Pr. M.A. Dupret)
Imaging characterization of the radial-velocity brown dwarf HD 18757B
Contact person : Anne-Lise Maire
e-mail : [email protected]
Tel : +3243669764
Office: B5c office 210
Availability: Can be defined upon email request.
Thematics : Astrophysics; Planetology and planetary systems
Description:
Most of the detection methods of exoplanets and brown dwarfs are more sensitive to objects closeto their star (within a few au) because of biases inherent to the techniques. On the other hand, directimaging is currently the most efficient technique to probe the population of brown dwarfs and giantexoplanets on wide orbits (>5 au). In the past years, a few radial velocity (RV) surveys have startedto target stars with slow RV drifts in order to detect the putative low-mass companions responsiblefor the long-period drifts and bridge the gap with the directly-imaged substellar companions. TheseRV surveys have shown a paucity of brown-dwarf companions within 5 au from the host stars withrespect to planetary and stellar companions, but also that their occurrence increases at largerseparations.
A survey with SOPHIE on the OHP telescope detected a potential brown-dwarf companion with anorbital period of ~109 yr around the nearby (24.2 pc) and old (11.4±0.1 Gyr) solar-type starHD18757. The corresponding projected semi-major axis is ~0.9±0.1 arcsec, making the companiona suitable target for direct imaging detection and characterization. Its orbital inclination cannot beconstrained from RV data so that only a minimum mass can be estimated, which makes itsconfirmation with direct imaging of prime interest to break the mass-inclination degeneracy andestablish its substellar nature. A non-detection of the companion by imaging using the CFHT/PUEOinstrument set an upper mass limit of 0.13 MS, making it a very good brown dwarf companioncandidate for deeper imaging at higher angular resolutions.
The goal of this Master thesis is to analyze direct imaging data of HD 18757 that our group ob-tained with the Large Binocular Telescope, to characterize HD 18757 B (relative position to the starand photometry), to derive its orbital parameters and mass, and to compare its properties to predic-tions of formation and evolutionary models of brown dwarfs. Our group at the University of Liègedeveloped the Vortex Image Processing package written in Python (Gomez-Gonzalez et al.2017)that will be used to process the LBT imaging data with state-of-the-art algorithms and characterizethe brown dwarf. We also developed a Markov-chain Monte Carlo orbital fitting code written in Py-thon (Maire et al. 2020) that will be used for the orbital analysis based on the LBT imaging data, theSOPHIE radial velocity data, and existing Hipparcos-Gaia astrometric data. Finally, the orbitalparameters and mass of HD 18757B inferred from the fit will be used with the measured luminosityand the age estimate of the system for detailed comparisons to predictions from several formationand evolutionary models (e.g., Saumon & Marley 2008, Bate 2009, Forganet al. 2015, Baraffe et al.2015). The imaging data will also be used to place constraints on the mass of additional companionsat wide separations in the system. [Describe here the context and the content of the proposed masterthesis. Recommended master courses can also be mentioned.
Vortex coronagraph optimization for habitable planet imaging with the ELT/METIS
Contact person : C. Delacroix, O. Absil
e-mail : [email protected], [email protected]
Tel: 043669758 (C. Delacroix), 043669724 (O. Absil)
Office: B5c (second floor)
Availability: any day (please contact us to agree on a time slot)
Thematics: Coronagraph design, adaptive optics instrumentation
Description:
The detection and characterization of exoplanets is one of the major science cases of modernastronomy. In this particular framework, the University of Liège has recently joined the METISconsortium, in charge of building the first-generation mid-infrared imager and spectrograph (2025+)for the future Extremely Large Telescope. Among other scientific goals, METIS will explore nearbySun-like stars and look for habitable exoplanets. To detect such faint planets close to their brighthost star, METIS will be equipped with several coronagraphs, designed to block out the direct lightfrom the star. One of the main challenges in designing a coronagraph for habitable planets, is toreach a high contrast at small separation angles, while maintaining enough throughput to eventuallycapture the photons from the planet.
Under the supervision of Christian Delacroix and Olivier Absil at the department of Astrophysics,Geophysics, and Oceanography (AGO), the goal of the master thesis will be to optimize the currentdesign of the vortex coronagraph (a concept developed at the ULiege and ideal at smallseparations), in particular the shape of the so-called Lyot-stop downstream the vortex phase mask.The master student will make use of the High-contrast End-to-End Performance Simulator(HEEPS), an in-house developed python software. The results of the master thesis are expected tocontribute to the scientific preparation of METIS.
Recommended master courses : SPAT0067 - Atmospheric and adaptive optics
Rocky planets from the TESS mission in the context of the SPECULOOS project
Contact person: Michaël Gillon, Francisco J. Pozuelos
e-mail: [email protected], [email protected]
Tel: MG: +32 4 3669743 / FP: +32 4 3669738
Office: MG: B5c, -1/1 / FP: B5c, +1/15
Availability: Due to the COVID-19 situation, video-calls are encouraged. The preferable time slotis from 10am to 1pm (Monday to Friday)
Thematics: Planetology and planetary systems
Description:
This research project aims to find nearby habitable rocky exoplanets suitable for atmosphericcharacterization with the next generation of telescopes that will be available in the near future suchas the James Webb Space Telescope (JWST) and the European-Extremely Large Telescope (E-ELT). This project will be conducted in the context of the SPECULOOS (Search for habitablePlanets Eclipsing Ultra-cOOl Stars) project and the TESS (Transiting Exoplanet Satellite Survey)mission. SPECULOOS (https://www.speculoos.uliege.be) is led by the University of Liège (PIMichaël Gillon) and aims to search for potentially habitable exoplanets around the smallest andcoolest stars in the solar neighbourhood. On its side, TESS (https://tess.mit.edu) is a NASA spacemission that is performing a survey of nearly the entire sky with the main goal of detectingexoplanets smaller than Neptune around bright and nearby stars. In this context there areoverlapping regions containing SPECULOOS targets which have been observed by TESS; however,due to their intrinsically low luminosities they might have gone unnoticed by the TESS detectionpipeline. The student will made use of dedicated pipelines to scrutinize gathered by TESS for a pre-existing list of SPECULOOS targets in the search for signals which might hint at the presence ofplanets. For each event that overcomes the vetting process, it will be proposed a ground-basedfollow-up campaign with the SPECULOOS network to rule out potential sources of false positivesand strengthen the evidence of their planetary nature.
Proposed Schedule:The training needed to develop the research project consists of:- Weeks 1-3: Familiarization with the tools, codes, pipelines and literature needed to understand thecontext of the project.- Weeks 4-9: Routine work with a larger degree of independence, where the student will develop themain project and will be encouraged to think of new approaches to solve problems, which willcontribute to the success of the project. During this period, the student will give a short talk topresent the work to date and provide the status of the project.- Weeks 10-12: The final stages of the project. The student will write a final report and present themain results in the department’s seminar.
Facilities and Monitoring: The student will be provided with a laptop, a work place in the existingstudents’ office and all the pipelines needed to process the data. The student will meet with the hostevery week to perform a weekly progress review of the project, where he/she will be able to expressdifficulties, new ideas etc. The student will be invited to join group meetings where other exoplanet-related topics are discussed.
Determination of meteoroid trajectories from radio observations
with the BRAMS network
Contact person : Emmanuel Jehin (ULiège), Hervé Lamy (IASB)
e-mail : [email protected], [email protected]
Tel : +32 (0)4 3669726, +32 (0) 2 3730418
Office: B5c 1/9
Availability: E. Jehin and H. Lamy will be available most afternoons in May and June
Thematics : Planetology and planetary systems
Description:
BRAMS (Belgian RAdio Meteor Stations) is a Belgian network of radio receiving stations whosepurpose is to detect and characterize meteoroids falling in the Earth’s atmosphere. The principle isbased on forward scattering of radio waves on ionized trails created along the meteoroid path. The
network consists of a dedicated transmitter located in Dourbes and of 30 receiving stations spread
along the Belgian territory. When a meteoroid enters the atmosphere, the radio wave can be re-flected temporarily by the ionized trail and be recorded by one or several receiving stations. Therecorded signal is called a meteor echo. The reflection of the radio wave is mostly specular, i.e. thepower at the receiver comes mostly from one small region along the meteoroid path centered on onepoint called the specular reflection point. The position of this point depends only on geometrical pa-rameters, namely the positions of the transmitter and receiver and the meteoroid trajectory. There-fore, the time of appearance of a meteor echo at different receiving stations will be slightly differentand depends on when these points are created along the path. These time differences can be mea-sured accurately because the stations are equipped with GPS clocks to synchronize the signals witha very good accuracy.
The candidate will work on a method using these temporal delays between meteor echoes recordedat various receiving stations in order to retrieve the trajectory of the meteoroid. It can be shown thata minimum of 8 stations detecting the same object are mandatory to apply this technique. In 2020,new receiving stations have been installed in Limburg in order to create a « cluster » of stationswhich are geographically close enough to ensure that most meteoroids are detected by at least 8 sta-tions. The candidate will mostly use these data to develop and validate the methods.
The candidate will also use data from the CAMS and FRIPON networks, which are optical net-works to provide trajectories from the brightest meteoroids detected in the same area. The candidatewill compare the results obtained for the trajectories retrieved with BRAMS data to those providedby these optical surveys.
This work will be done in collaboration with the BRAMS team (PI : Hervé Lamy) working at BISA(Belgian Institute for Space Aeronomy) and with the FRIPON team (PI : François Colas) workingat Observatoire de Paris.
Search for Solar System objects in TRAPPIST telescopes archive images
Contact Person: Emmanuël Jehin
e-mail: [email protected]
Tél: (0)4 3669726
Office: B5c 1/9
Availability: please contact me
Thematics: Astrophysics (small bodies of the solar system)
Description:
The TRAPPIST telescopes installed at the la Silla observatory in Chile in 2010 and in Morocco in2016 by our team are dedicated to the research and the study of exoplanets in transit and the studyof the small bodies of the Solar System (comets and asteroids). Each night, since 10 years in Chileand 4 years in Morocco we collect hundreds of images of one or two fields during several hours tosearch for exoplanets in transit. This constitutes a unique dataset of about 2.5 million images to beexplored to discover new asteroids and comets.In this work we propose the fine tuning and the use of a recently developed pipeline to detect asmany moving objects of the Solar System as possible in those archive images. Among these objectsmost will be already known asteroids but sometimes also a new object still unknown will be found.As some fields are observed several nights in a row and for many hours it will be possible to buildrotation light curves for many of these objects. By adapting the pipeline it is also possible to findobjects that move more slowly like distant comets and Trans-Neptunian objects or faster like NearEarth asteroids.Objectives: adapt the detection strategies according to the type of objects to detect (close Near EarthAsteroids (NEA), or very distant Trans-Neptunian Objects (TNO)) and run the pipeline forautomatic detection on the archive database. Collect from the results of the pipeline for each nightthe astrometric data and check the identification of the objects found. Submit the measurements ofthe unknown objects to the Minor Planet Center (MPC). Collect also the photometric measurementsfor each target found and build their light curves to try to find the asteroid rotation period. Most ofthese rotation light curves will be new and might be published in a paper.
https://www.trappist.uliege.be/cms/c_5006023/fr/trappist
Study of the chemical composition of comets atmospheres using the TRAPPIST telescopes
Contact person: Emmanuël Jehin (ULiège)
E-mail: [email protected]
Tél: (0)4 3669726
Office: B5c 1/9
Availability: please contact me
Thematic: Astrophysics (small bodies of the solar system)
Description:
Comets are among the best preserved specimens of the primitive solar nebula. This status of“fossils” gives them a unique role in understanding the origins of the solar system. The success ofthe Rosetta space mission was very important and is changing our knowledge about comets. But itshowed also that observations from the ground continue to be important: they make it possible tosupplement the data in situ by obtaining information on larger scales of the coma and tails, and for amuch larger number of comets, which is necessary to extrapolate the results to the entire cometarypopulation. The link between the composition of comets and their dynamic history must still beclarified and a complete comet classification is still missing.
In this context, we propose the observation and analysis of the coma of two or three bright cometswith the TRAPPIST telescopes network. These robotic telescopes installed by our team in Chile (in2010) and in Morocco (in 2016) are equipped with narrow band filters to isolate the emissions ofdifferent gases and dust contained in the atmosphere of comets. The student will have to prepare theobservations, calibrate the data and calculate the production rates of the different gases using the so-called Haser model (1957). The necessary tools for this kind of measures have already beendeveloped in our team. The student will have to become familiar with the various techniques, adaptand improve if necessary the reduction procedures and scripts and run the models. The results mightlead to the publication of a short article.
The work will be done in the comet group of the OrCa Service (+1) and the TRAPPIST team https://www.trappist.uliege.be/cms/c_5006023/fr/trappist
Characterising the different components of the Jovian aurorae with Juno-UVS observations
Contact person : Bertrand Bonfond
e-mail : [email protected]
Tel : +32/366.97.72
Office: B5c 0/2
Availability: From Monday to Thursday afternoon. Please send an email in advance. Skype is alsoa possibility.
Thematics : Planetology and planetary systems
Description:
Juno is a NASA mission dedicated to the exploration of the planet Jupiter. It orbits around the giantplanet since July 2016, bringing a wealth of discoveries and unprecedented observations. Among itsinstruments sits an imaging spectrograph (Juno-UVS) dedicated to the observations of the Jovianaurorae. The most prominent feature of the Jovian aurorae is an incomplete curtain centred aroundthe magnetic pole and called the main emissions. The main emissions also mark the boundary of thetwo other regions of the aurorae: the polar emissions and the outer emission, equatorward of themain emissions. The student will use the image processing tools developed at the Laboratory forPlanetary and Atmospheric Physics (www.lpap.uliege.be) to monitor the evolution of the emittedpower in these three regions on the Juno-UVS dataset. The student will then characterize the globalmorphology of the aurora and interpret their meaning in terms of magnetospheric physics.
The courses SPAT0028-2 and/or SPAT0023-1, as well as SPAT0032-2 are highly recommended.
Whitening of Doppler data in Radioscience
Contact person: Promotor: Véronique Dehant; Co-Promotor: S. Le Maistre
e-mail: [email protected] and [email protected]
Tel: 02 373 0266 (V. Dehant)
Office: Royal Observatory of Belgium
Availability: any time by skype; please email to decide when
Thematics: Planetology
Description:
The ground stations tracking satellites on Earth, the DSN (Deep Space Network - NASA) and ESTRACK(European Space Tracking – ESA) communicate directly with the spacecraft (S/C) using uplink (Earth →S/C) and downlink (S/C → Earth) radiosignal in X-band, S-band or Ka-band.
When the Earth is in the field of view of the S/C antennas, when the S/C is in the field of view of the Groundstation (GS) antennas, and when programmatic allows it, the S/C transmit their data in a limited time(telemetry) and the GS transmit the commands for operating the S/C and its instruments. The scientific datathat we are interested in in this case are the tracking Doppler data provided by the downlink at the DSN andESTRACK either in One-Way (S/C → Earth or Two-Way (Earth → S/C → Earth). Data are often temporallycorrelated and therefore require pre-processing. The objective of this master thesis is to apply an algorithm ofdata whitening in order to decorrelate them and better dig out the Doppler signal out of the noise.
The method will be tested on and applied to the NASA InSight radioscience data (on the surface of Marssince November 2018).
This work can lead to a publication and be continued into a PhD thesis (application to real data of otherradioscience data such as the future ExoMars 2020 data of the Belgian instrument LaRa).
Task description:
- Examine the different whitening algorithms that allow to process highly noisy data and compare their re-spective performance.
- Implement in MATLAB the whitening algorithm that will minimize the noise present in the Dopplerdata (DSN and ESTRACK files).
- Application to the Radioscience InSight data.
Effect of charged particles on Doppler tracking
Contact person: Promotor: Véronique Dehant; Co-Promotor: S. Le Maistre and N. Bergeot
e-mail: [email protected], [email protected], and [email protected]
Tel: 02 373 0266 (V. Dehant)
Office: Royal Observatory of Belgium
Availability: any time by skype; please email to decide when
Thematics: Planetology
Description:The aim of this study is to analysis the effects of plasma turbulence in the solar wind on Doppler radiomeasurements from interplanetary spacecraft.A spacecraft receives an uplink signal at X-band (7.3 GHz), and transmits data (telemetry or science data) toEarth at X-band (8.4 GHz). In addition, a small amount of downlink power is transmitted at S-band (2.3GHz) for evaluating the link performance. The two-way communication involves a 34-m ground station onthe Earth that is equipped to emit an X-band signal and to receive both X- and S-band signals. At the groundstation a loop tracker records carrier phase at both downlink carriers and this data is analyzed to examine theeffect of charged particles, from solar plasma and the Earth’s ionosphere, on Doppler passes typically usedfor tracking and navigation of interplanetary spacecraft. The Doppler tracking data allows, for example,calculating the gravitation field of the planet around which the spacecraft is orbiting. The experimental dataset that will be used in this study are dual-frequency tracking of the European Space Agency’s (ESA) MarsExpress (MEX) spacecraft.
Task Description :
Based on the power spectral analysis of the dual-band data, the objective of this work is to determine anappropriate model for treating charged particles in single-band Doppler tracking. The statistic of phasevariations will be described in terms of Allan variances (root-mean-square differenced-phase variations) andclassical frequency variance. A realistic modelling of the charged particle variations should be adopted ingood agreement with current models developed to estimate the solar plasma variations as a function of SEPangle.
This work can lead to a publication and can be continued in a PhD thesis.
Effects of the meteorite and comet impacts on the degassing of volatile contained in theicy soil
Contact person: Promotor: Véronique Dehant; Co-Promotor: E. Gloesener
e-mail: [email protected] and [email protected]
Tel: 02 373 0266 (V. Dehant)
Office: Royal Observatory of Belgium
Availability: any time by skype; please email to decide when
Thematics: Planetology
Description:
Mars past: Geological evidences suggest that Mars underwent a period in the beginning of its history wherethere was liquid water. Early in its history, Mars had a denser atmosphere with sufficient greenhouse gases tosustain the presence of stable liquid water at the surface. Impacts by asteroids and comets have played asignificant role in the evolution of the martian atmosphere, not only by causing atmospheric erosion but alsoby delivering material and volatiles to the planet. A period with intense bombardment of meteorites couldhave increased the atmospheric loss, but to explain the loss of a speculative massive atmosphere in the LateNoachian (< 3.5 Ga), other factors of atmospheric erosion also need to be taken into account. CO 2 andmethane (CH4) may well be part of this process, with potential storage in the martian regolith, in clathrates.Clathrates or gas hydrates are crystalline compounds formed by the inclusion of gas molecules in the cavitiesof water molecules network and are typically stable at high pressure and low temperature. These clathratescould have remained stable at depth over geologic time.
Mars present: The discovery of methane on Mars is a very fascinating subject because it could possibly berelated to past or present life... However, this is not the only explanation as it could be related to degassing ofclathrates. Nowadays, martian methane remains surrounded by a lot of mystery as its source and sink areunknown. Its observed spatial and temporal variations challenge our current understanding of atmosphericchemistry and physics and, as a result, its presence on the Red Planet is still debated today. The ExoMarsTrace Gas Orbiter (TGO), currently in orbit around Mars, provides new CH 4 data. This mission, launched in2016 is specially designed to detect methane and other trace gases. The scientific team of TGO recentlyannounced that they did not find methane while the presence of methane has been detected at the surface ofMars by Mars Science Laboratory (MSL). The destabilization of clathrates in regions where methane hasbeen locally reported requires considering processes such as seismic activity or impacts.
This work: Meteorite and comet impacts still exist on Mars and may play a role in the degassing of methanetrapped in clathrates as the impact may increase the surface and subsurface temperatures. However, this hasnever been demonstrated. The idea of the work is to investigate temperature and pressure changes followinga small impact in order to compute methane degassing in the atmosphere of Mars from the regolith whendestabilizing the clathrates. This work has already started with a Master thesis last year and will be continuedthis year.
Task description:
- Get familiar with existing codes for computing methane degassing- Compute the temperature associated with an impact- Verify if this allows degassing of methane.
This work can lead to a publication and can be continued in a PhD thesis.
Rotation of Mars from SBI radioscience measurements
Contact person: Promotor: Véronique Dehant; Co-Promotors: S. Le Maistre, M. Yseboodt
e-mail: [email protected] [email protected] et [email protected]
Tel: 02 373 0266 (V. Dehant)
Office: Royal Observatory of Belgium
Availability: any time by skype; please email to decide when
Thematics: Planetology
Description:
The SBI (Same Beam Interferometry) technique can provide very precise measurements of the distancedifference between two spacecraft or landers. This involves simultaneously tracking two or more landerswith identical transponders from a single antenna on Earth. The radio signals emitted are relayed by thelanders to the Earth station, where they are recorded and then combined in an interferometric mode to form adifferential phase measurement. Since the media crossed by the two signals (for example the interplanetaryplasma or the Earth's atmosphere) are the same, these sources of error are largely canceled out in the case ofan SBI measurement.
These measurements will make it possible to observe precisely the deformations of the surface of Mars dueto the tides as well as its rotation, which will add precise constraints on the interior of Mars (such as the stateand the size of the nucleus for example) as well as on mass exchanges between the polar ice caps and theatmosphere.
For the proposed work, simulations will be carried out to quantify the contribution of this type ofmeasurement on our knowledge of the parameters of rotation and tide. Measurements are generated and thenused to extract interesting information and to see what level of precision is possible. This allows to testdifferent mission configurations and see which one is most conducive to the experience.
It will also be asked to test new configurations such as for example a lander on Mars, the second being onPhobos, one of the moons of Mars.
The software used was developed at the Royal Observatory of Belgium in the case of Doppler and SBImeasurements between a Martian lander and the Earth. The orbital movement of Phobos around Mars willhave to be added to the software then simulations will have to be performed and analyzed for manyconfigurations, in order to see which is the best mission strategy.
This work can lead to a scientific publication.
Task description:
- Get familiar with existing codes for computing SBI measurements- Compute the associate Mars interior parameters- Determine the best strategy to obtain the best information.
This work can lead to a publication and can be continued in a PhD thesis.
Analysis of EPT and SATRAM data for the assessment of the use of radiation monitordata for space weather purposes
Contact person: Promotor: Véronique Dehant; Co-Promotors: Sylvie Benck, Stanislav Borisov
e-mail: [email protected] [email protected] and [email protected]
Tel: 02 373 0266 (V. Dehant)
Office: Royal Observatory of Belgium
Availability: any time by skype; please email to decide when
Thematics: Planetology
Description:
Radiation monitors (like SATRAM - Space Application of Timepix based RAdiation Monitor) are carried onboard space vehicles where they operate as radiation safety devices and alert systems. The data that theyrecord are related to radiation doses or flux variations and can be used to take mitigation measures againstradiation effects on crew and equipment whenever critical conditions are arising. Radiation monitors arecompact, light, and require a few watts of power budget. Sometimes, their measured quantities are convertedinto particle fluxes using rather complex procedures, the developments of which were spurred by the need tomake the most of every radiation monitor given that the latter had more flight opportunities. However,limited particle discrimination capabilities, poorly defined Field-Of-View (FOV) and the resulting inaccuratedetection efficiencies, sum up to affect the level of confidence that users have, partly or entirely, in the finalflux data. As a consequence, radiation monitors flux data sets are assumed to be correct when they agree withvalidated radiation data or model, but they do usually not lead to model questionings or to challenging ofspace radiation science, when discrepancies are revealed.On the other hand, science-class space radiation spectrometers (e.g. EPT - Energetic Particle Telescope) aredeveloped to perform the absolute flux measurements required for scientific studies, including among others,particle acceleration mechanisms, angular distribution variations, conditions for generation of new radiationbelts and particle precipitation rates. The data acquired by such kind of spectrometers (flux-energy spectra)are also used to validate space radiation models and in cross-calibration of radiation monitors. Science-classinstruments are required to cover a significant energy range, to achieve absolute particle type identification,to provide high energy resolution and to feature a good FOV definition, with less severe constraints on mass,volume and power consumption budgets.The objective of this work is to verify what could be the best usage of advanced radiation monitor data forscientific analysis in space physics. We have the impression that the Pixel detector technology can providefairly good data that could complement spectrometers under certain conditions. The analysis wouldconcentrate on the SATRAM data in comparison with EPT data. Both instruments are actually flyingonboard Proba-V spacecraft and therefore cross-comparison is supposed to be straightforward. This analysiswill also give us hints for further instrument developments.
This master thesis can lead to a publication and can open to a PhD thesis on that matter.
Task description:
- Get familiar with spectrometers and radiation monitors (EPT and SATRAMon Proba-V)- Compare SATRAM data in comparison with EPT data- Determine complementarities of the data.
This work can lead to a publication and can be continued in a PhD thesis.
Computation of the TEC (Total Electron Content) in the ionosphere from nanosat GNSSdata
Contact person: Promotor: Véronique Dehant; Co-Promotors: Ozgur Karatekin, Nicolas Bergeot, Florian Bodranghien
e-mail: [email protected] [email protected] [email protected] and [email protected]
Tel: 02 373 0266 (V. Dehant)
Office: Royal Observatory of Belgium
Availability: any time by skype; please email to decide when
Thematics: Planetology
Description:
The satellites of the American GPS system are at an altitude of about 20,000 km, those of the RussianGLONASS system at an altitude of about 19,000 km, and those of the European GALILEO system at analtitude of about 23,000 km. All these GNSS satellites (Global Navigation Satellite System) actuallyoverlook a large number of low satellites equipped with GNSS receivers, including nanosatellites which willbe launched in the future (> 2019) by the firm Aerospacelab. The radiofrequencies used are each time atleast greater than 2; this makes it possible to combine the frequencies to obtain the TEC (Total ElectronContent), that is to say the electron content of the ionosphere. The Earth's ionosphere is a region outside theatmosphere that contains a high concentration of free electrons. We now know that electrical events occurwhen clouds of charged particles are projected by the solar wind or by a solar flare or Coronal Mass Ejection(CME). When the eruption is intense, if the Earth is in the path of charged particles, the result can becatastrophic for all communication systems. It is therefore necessary in the future to monitor the activity ofthe Sun and its effects on our atmosphere (we speak of space weather), and in particular to measure the TEC.In this context, Aerospacelab has equipped and will equip its nanosatellites with GNSS receivers. Themaster thesis consists in studying the geometry of the orbits of the different satellites in play to see what canbring future nanosatellites to our knowledge of the ionosphere and in particular in the layers close to theheight of cube-satellites. If data is already available, we can also apply what will be developed.
This work can lead to a scientific publication and extend into a doctoral thesis.
Task description:
- Get familiar with GNSS data analysis and TEC- Use the geometry of the GNSS to determine TEC- Determine what this can bring to TEC maps
Prediction of the amplitude of the Chandler wobble mode of Mars from atmosphericexcitation
Contact person: Promotor: Véronique Dehant; Co-Promotors: Ozgur Karatekin, Sébastien Le Maistre, Orkun Temal
e-mail: [email protected] [email protected] [email protected] and [email protected]
Tel: 02 373 0266 (V. Dehant)
Office: Royal Observatory of Belgium
Availability: any time by skype; please email to decide when
Thematics: Planetology
Description:
The Martian atmosphere is very thin but participates in the process of sublimation and condensationof the polar caps. A quarter of this atmosphere condenses in the poles according to the seasons.These mass movements induce variations in the rotation of Mars and a polar motion. Thismovement has seasonal components. There is also a free oscillation mode, the Chandler wobble,which would be excited by the atmosphere. The master thesis consists in calculating the amplitudesof the polar motion linked with the Chandler wobble using the outputs of a general circulationmodel of the Martian atmosphere.This work can lead to a scientific publication and extend into a doctoral thesis.
Task description:
- Get familiar with GCM of the Martian atmosphere- Compute polar motion excitation- Compute CW excitation
Processing of Planetary Radio Interferometry and Doppler Experiment (PRIDE)experiment
Contact person: Promotor: Véronique Dehant; Co-Promotors: Sébastien Le Maistre, Dominic Dirkx
e-mail: [email protected] [email protected] and [email protected]
Tel: 02 373 0266 (V. Dehant)
Office: Royal Observatory of Belgium
Availability: any time by skype; please email to decide when
Thematics: Planetology
Description:
The Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique exploits the radiotransmitting capabilities of spacecraft from the most modern space science missions. A very highsensitivity of Earth-based radio telescopes involved in astronomical and geodetic Very LongBaseline Interferometry (VLBI) observations and an outstanding signal stability of the radiosystems allow PRIDE to conduct precise tracking of planetary spacecraft. The data from individualtelescopes are processed both separately and jointly (involving correlators) to provide Doppler andVLBI observables, respectively. The accurate examination of the changes in phase of the radiosignal propagating from the spacecraft to each of the ground radio telescopes on Earth make the“open-loop” Doppler observables derived from each telescope very useful for different fields ofplanetary research. The Doppler data are called “open-loop” as the receiving ground station doesnot lock on the signal but receives the signal as it is in a frequency band around the expectedreceived signal. “Closed-loop” Doppler data obtained by deep space tracking networks, such as theNASA Deep Space Network (DSN) and the ESA tracking station network (ESTRACK), areroutinely used for navigation and science applications. The Doppler data are called “closed-loop” asthe receiving ground station has the technical capability to lock on the signal.
For the future LaRa (Lander Radioscience) experiment that will be launched to Mars in 2022, weenvisage to use this “open-loop Doppler” technique in order to increase the precision on the data.By tracking the LaRa signal, Earth-based radio telescopes involved in the PRIDE experiment canprovide open-loop Doppler tracking data. The technique of processing the data is very different for“open-loop Doppler” compared to “closed-loop” Doppler, and will have to be fully developed. Thepartnership with JIVE (Joint Institute for VLBI ERIC) and the Technical University Delft will helpus to use existing codes and not to start from scratch.
Task description:
- Get familiar with open-loop data processing- Application to LaRa- Compute of the improvement
Reconstruction of missing data in satellite observations using a neuralnetwork
Contact person : Alexander Barth, Aida Alvera-Azcárate, Jean-Marie Beckers
e-mail : [email protected], [email protected], [email protected]
Tel : 0/43663664
Office: B5 2/56
Availability: Upon request (tentative dates are 18 and 25 May 2020)
Thematics: environment and oceanography
Description:
Satellite observations working in the optical and infrared bands are affected by clouds and thereforesatellite images can have large gaps due to clouds. The GHER has recently developed a method toreconstruct missing data using a neural network called DINCAE (Data-Interpolating ConvolutionalAuto-Encoder) and applied it to sea surface temperature. The aim of this master thesis is to test andextend this method with several remote sensed parameters (sea surface temperature, Chlorophyll-a,surface wind) jointly in order to take advantage of their relationships and to improve thereconstruction.
More information
https://github.com/gher-ulg/DINCAE
https://www.geosci-model-dev.net/13/1609/2020/gmd-13-1609-2020.pdf
http://data-assimilation.net/upload/Alex/DINCAE/data-avg-DINCAE-AVHRR.gif (Examplereconstruction)
Recommended lectures:
Satellite oceanography (OCEA0087-1)
Data acquisition and analysis, complements (OCEA0035-1)
Studying the dynamics near a canyon using a hydrodynamical ocean model
Contact person : Alexander Barth, Aida Alvera-Azcárate, Jean-Marie Beckers
e-mail : [email protected], [email protected], [email protected]
Tel : 0/43663664
Office: B5 2/56
Availability: Upon request (tentative dates are 18 and 25 May 2020)
Thematics: environment and oceanography
Description:
A hydrodynamical ROMS model of the Ligurian Sea with an increased resolution on the regionaround the Bay of Calvi has been implemented (model simulation showing sea-surfacetemperature). Starting from this existing model, new simulations will be conducted adapting theinitial conditions, boundary conditions and forcing fields. The model solution should be validatedusing high-resolution satellite observations. The focus of this master thesis will be the currentvariability in the canyon near the Bay of Calvi, which is important for the transport of nutrients andthe ecosystem as a whole. In particular, the question of how large-scale currents affect thevariability in the canyon will be addressed.
Recommended lectures:
Structure and application of numerical ocean models (OCEA0036-1)
Satellite oceanography (OCEA0087-1)
Climatologies in the Calvi Bay (Corsica)
Contact person : Alexander Barth, Aida Alvera-Azcárate, Jean-Marie Beckers
e-mail : [email protected], [email protected], [email protected]
Tel : 0/43663664
Office: B5 2/56
Availability: Upon request (tentative dates are 18 and 25 May 2020)
Thematics: environment and oceanography
Description:
Climatologies represent the mean state of the ocean or sea and allow us to assess the importance ofchanges around this mean state. While we have a relatively good understanding of the mean state ofthe ocean at large spatial scales. The understanding of the coastal areas is limited. The master thesisaims to derive climatologies of the Bay of Calvi by combining in situ observations from differentdata repositories, including the RACE (Rapid Assessment of the Coastal Environment) database.The parameters (e.g. temperature, salinity, oxygen, chlorophyll-a concentration) are then griddedwith a tool called DIVAnd developed at the GHER to produce climatological fields that can be usedas background information for other studies. The climatology developed in this master thesis will beused to study long-term trends.
Recommended lectures:
Data acquisition and analysis, complements (OCEA0035-1)
Data assimilation and inverse methods (OCEA0097-1)
Study of the 2019 marine heatwaves in the western MediterraneanSea with DINEOF
Contact person : Aida Alvera-Azcárate, Charles Troupin, Jean-Marie Beckers
e-mail : [email protected], [email protected], [email protected]
Tel : 0/43663664
Office: B5 2/56
Availability: Upon request
Thematics : environment and oceanography
Description:
Marine heat waves are extreme warming events that can have a strong impact on the ecosystem.Two of these events took place in the western Mediterranean Sea in summer 2019 (http://dineof.net/DINEOF/dineof_July2019.html). These will be studied by analyzing cloud-freeSea Surface Temperature satellite data. The cloud-free data will be calculated by means of DINEOF(Data Interpolating Empirical Orthogonal Functions), developed at the GHER. The causes of thesemarine heatwaves and the total heat anomaly, compared to previous years, will be studied. Thepenetration of the warm anomaly on the water column, at different places in the westernMediterranean Sea, will be assessed with in situ data.
Recommended lectures:
Data acquisition and analysis, complements (OCEA0035-1)
Satellite oceanography (OCEA0087-1)
Analysis of the generation of cloud bands on Jupiter or Saturn
Contact person : Jean-Marie Beckers, Denis Grodent
e-mail : [email protected], [email protected]
Tel : +3243663358
Office: B5a 2/5
Availability: Preferentially monday’s afternoon.
Thematics : Planetology, Geophysical Fluid Dynamics
Description:
Cloud bands are visible both on Jupiter and Saturn with a strong zonal flow direction alternatingfrom the equator to the poles. The proposed work aims at analysing the dynamics leading to suchbehaviours, focussing on one of the two planets.
The student will start with an analysis of the different explanations provided up to now, includingtheir hypothesis on thermodynamics and geometrical constraints (barotropic or baroclinic modes,vertical extensions and dynamics, small-scale turbulence effects etc). Based on the currentknowledge of Jupiter’s or Saturn’s atmosphere, a model providing a good compromise betweenrealism and simplicity will be chosen for further investigation. In particular, the idealized modelwill then be used to simulate how coherent structures as a big vortex or the bands can emerge andunder which conditions involving geostrophic turbulence and planetary waves. Testing hypotheseswill typically include activating or deactivating certain processes during the simulations. The focusof the work is thus the understanding of the underlying dynamics and less the best reproduction ofobservations.
f the analysis turns out to be strongly dependent on a poorly known parameter, the study couldactually be turned into an inverse problem. In that case, using actual observations on the banddistributions, the parameter could be calibrated and the thesis provide an indirect estimate for it.
The work will rely on a good understanding and analysis of fundamental geophysical fluiddynamics and the use of numerical models.
Interpolation of SWOT altimetry data using variational methods
Contact persons: Charles Troupin
E-mails: [email protected]
Office: B5a, 2/11
Availability: Afternoon except Wednesday.
Thematics : Oceanography (remote-sensing)
Description:
SWOT stands for Surface Water and Ocean Topography (https://swot.jpl.nasa.gov/) is a missionfocused the world's oceans and its terrestrial surface waters. The SWOT satellite will provide oceansurface measurements with an unprecedented resolution, over a 120 km wide swath with a ~20 kmgap along nadir. This particular spatio-temporal data distribution makes it necessary to use specificinterpolation techniques to create gridded fields of sea surface height.
While the satellite is expected to be launched in April 2021, the SWOT simulator(https://github.com/SWOTsimulator) already provides artificial SWOT measurements on seasurface height with simulated errors based on numerical ocean simulations. Such a dataset could beused to perform some tests in order to prepare for the real data coming after the satellitedeployment.
The proposed work consists in:
1. Making an inventory of the interpolation techniques usually applied to
altimetry data and to simulated SWOT measurements.
2. Apply the DIVAnd (https://github.com/gher-ulg/divand.jl) tools on simulated
SWOT data in a selected region and assess:
the computation time,
the quality of the gridded fields and
the estimation of the analysis parameters.
Development of a spectral radiative module for oceanographic models
Contact person: Marilaure Grégoire
e-mail : [email protected]
Tel : 043663354
Office: B5a, 2nd floor, 2/50
Availability: email contact to fix an appointment
Thematics: Climate, environment and oceanography
Description:
The in-water-irradiance is a key variable in oceanography that governs the heat distribution,primary production and photo-chemical reactions. An accurate representation of the ocean physicsand biogeochemistry by ocean numerical models hence requires an accurate calculation of the in-water irradiance. However, if marine ecosystem models become more and more sophisticated interms of food chain representation, the optical calculation is still very often oversimplified. The aimof the master thesis is to improve the representation of light penetration in an existing oceannumerical model and to assess how it improves model performances. The light penetrating in the ocean is modified by interactions between photons and a molecule ofseawater itself, or the pigment in dissolved organic material or contained in a phytoplankton cell, ora particle in suspension. These interactions result in absorption and scattering of the incoming solarirradiance. If the light is scattered before being absorbed, then it may be scattered back out of thesea and be measured by remote sensing. The distribution of the optically active components (e.g.chlorophyll a, suspended sediment and colored dissolved organic matter) is not uniform and ratherexhibits large spatial and temporal gradients especially in coastal areas. The variability in thedistribution of optically active substances and the difference in their absorption and scatteringspectra challenge the retrieval of water constituents (e.g. chlorophyll) from remote sensing. The master thesis is targeted towards the development and implementation of a computationallyefficient radiative transfer model (RTM) describing the distribution of in-water irradiance (thediffuse and direct parts) along the vertical and in different spectral bands corresponding to thosetypically used in remote sensing and in particular in the Sentinel 3 Ocean and Land ColorInstrument (OLCI). The penetration of spectral irradiance will be described considering itsabsorption and scattering at different wavelengths by various optically active components. State ofthe art formulations that link absorption and scattering properties to the biomass of optically activeconstituents will be used. The main purposes here are 1) to obtain a better estimation of the in-waterirradiance that is expected to improve the quality of model predictions (biogeochemistry andphysics) and 2) to simulate radiometric properties that can be directly linked to observations, andexempt validation/calibration/assimilation efforts from the use of empirical equations that linkobservations and modelled variables (e.g. the equation that links reflectance to chlorophyll-a). Theapproach will be validated using radiometric measurements provided by remote sensing and fielddata like BGC-ARGO, AERONET-OC and BIOMAP products.
Modelling marine ecosystem in the Belgian Coastal Zone and SouthernBight of the North Sea: Testing models at different complexities.
Contact person: Marilaure Grégoire
e-mail : [email protected]
Tel : 043663354
Office: B5a, 2nd floor, 2/50
Availability: email contact to fix an appointment
Thematics: Climate, environment and oceanography
The North Sea, and in particular, the Belgian Coastal Zone (BCZ), have been submitted to varioushuman activities with for instance, the deployment of offshore wind farms, dredging, aquacultureand eutrophication. With the view to assess the impact of human activities on the health of theenvironment, a mathematical model simulating the hydrodynamics, waves and sediment transporthas been implemented and run for several years. The aim of the master thesis is to couple ecosystemmodels at various complexities (but relatively simple) to simulate the biogeochemical cycle ofnitrogen in the southern bight of the North Sea. The student will have to couple and run the couplephysical and biogeochemical models, validate its results in comparison with satellite products andin -situ data and analyse a typical year and compare model performances as a function of modelcomplexity.
Specific method, material used:
An existing biogeochemical model coded in FORTRAN. The student is not expected to be able tochange the models but should be familiar with or willing to learn software such as R, python ormatlab in the purpose of analyzing model outputs and comparing them with observations.
Modelling biogeochemical cycles in the Global Ocean
Contact person: Anne Mouchet, Marilaure Grégoire
e-mail : Anne Mouchet [email protected], [email protected]
Tel : 043663354
Office: B5a, 2nd floor, 2/50
Availability: email contact to fix an appointment
Thematics: Climate, environment and oceanography
Description:
Ocean deoxygenation has the potential to alter the global cycling of essential biogeochemicalelements like carbon (C), nitrogen (N) and phosphorus (P) with consequences of the Earth Climateand life that we hardly know. The expansion of Oxygen Minimum Zones (OMZs) and AnoxicMarine Zones (AMZs) in the global and coastal ocean in response to climate change andeutrophication is intensifying the loss of fixed N through denitrification. Mathematical modellingallows to investigate the mechanisms implied in the modifications of our ocean and allows to assesstheir relative importance. In this master, thesis, the student will run an existing biogeochemicalmodel (BAMHBI) to simulate the cycling of nitrogen, phosphorus and oxygen in the Global Ocean.The biogeochemical model is forced by the outputs of an existing physical model of the ocean (i.e.NEMO) that solves the hydrodynamical fields with a resolution of 2°. The coupling between thebiogeochemical and physical model is already done.
The student will have to 1) run the configuration for the Global Ocean, 2) analyze the results usingappropriate statistical tools, 3) based on the results analysis and comparison with observations,improve selected model formulations, 4) when the results will be satisfactory, compute diagnostics(e.g. primary production, denitrification, oxygen consumption).
Specific method, material used:
An existing biogeochemical model coded in FORTRAN. The student is not expected to be able tochange the model but should be familiar with or willing to learn software such as R, python ormatlab in the purpose of analyzing model outputs and comparing them with observations.