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<p>Mars’ Polar layered Deposits (PLD) accumulated over the last few millions of years due to seasonal buildup of frost trapping atmospheric gasses and incoming sediments, thereby preserving the history of Mars' recent climate in the form of an ice-rich geologic record. The PLD includes both the North Polar Layered Deposits (NPLD) and the South Polar Layered Deposits (SPLD) which are estimated to be up to 5 Mya and 100 Mya old respectively. Characterizing the contents of these deposits is essential to understand the role of geologic and climatic processes recently active on Mars. The Mars scientific community recommends robotic exploration of these icy NPLD to sample the ice and extract recent climate records; however, linking the geologic record to the climatic history will require quantitative dating of the NPLD. The SPLD is thought to be older than the north polar deposits, so the stratigraphic records of the SPLD are a window to look deeper into the climatic history of Amazonian Mars. Deciphering the paleoenvironment at the PLD requires characterization of the ice-rich deposits, however, the origin, composition, transport histories, and alteration environment of sediments within the deposits are not well constrained.</p> <p>In this study we use orbital reflectance spectroscopy to show for the first time that dateable mafic lithics are present throughout the PLD. We find significant glass as well as diverse crystalline minerals, which suggests that surface processes like impacts and volcanism were active during the late Amazonian and transported sand-sized and finer sediments from across the planet to the poles. In situ investigation of the PLD will thus provide critical quantitative age constraint on both the recent geologic and climatic histories of Mars. Previous studies have confirmed widespread detection of sulfates at the NPLD and here we show that sulfates dominate the alteration mineralogy at the SPLD suggesting acidic, oxidizing, and evaporitic conditions. Based on this more extensive survey, previously reported rare detection of smectites and hydrated silica in the SPLD is likely due to ballistic emplacement by impacts from targets on surrounding smectite-bearing Noachian terrains.</p> <p>Detrital ice-rich sediments within the PLD are a complex mixture of mafic minerals and weathering products from multiple sources and are continuously reworked. In order to investigate the material and grain-size dependent effects of chemical and physical weathering in a cold and wet basaltic environment, a rover-based Mars analog study is conducted in the glacio-fluvial-aeolian landscapes of Iceland. A DCS-based color analysis technique is employed in tandem with VNIR spectroscopy and XRF analysis to develop a strategy for conducting sediment provenance. We observe that DCS-based color analysis is a powerful tool for identifying spectral diversity, and that it has the capability to differentiate primary minerals from alteration minerals. Because color analysis can aid in identifying diverse targets for sampling within the rover’s workspace, tactically, DCS colors can be used during operations to link detrital sediments within the rover’s vicinity to surrounding bedrock sources. DCS images enhance our ability to correlate observation of surface features from orbit, extend local mineralogical interpretation to surrounding regions, optimize rover’s traverse and select science targets. </p>

Ionospheric effects are one of the factors that can have negative impact on Global Navigation Satellite Systems (GNSS). Those effects can be called medium-scale traveling ionospheric disturbances (MS-TIDs) at middle latitude regions and polar cap patches at high latitude regions. The ionospheric variations have different patterns for each region and time. The statistical measures of the ionospheric variation are analyzed presented as functions of time in half solar cycle, annual seasonal, and time of day for four geographical locations in Sweden. By processing achieved GPS data from a 7-year period, 2013-2020, from SWEPOS, the characterization of the ionospheric variation was performed. It is found that the ionospheric variation is larger for the Norra Norrland region during solar minimum. However, during solar maximum, the variation depends on the seasons but high variation seems to occur the most in Svealand region. For the more northern regions (Norra and Södra Norrland), the ionospheric variation is greater during nighttime than during daytime, while for the more southern regions (Svealand and Götaland), the variation is greater during daytime. At solar maximum, the variability is higher during the months March, May, September, and October and smaller in June, July, and August. For the ionospheric variation prediction, a model based on Recurrent Neural Network (RNN) called Long Short-Term Memory (LSTM) is proposed. The tuned hyperparameters for LSTM are tested for the prediction accuracy by comparing the predicted values to the measured values. It is found that the LSTM can yield the prediction results with more than 90% accuracy when using 1-6 hours of input data and aiming for 10-35 minutes of output data. Longer duration of input and output results in lower accuracy of the predicted values. / Jonosfäriska effekter är en av de faktorer som kan ha negativ inverkan på Global Navigation Satellite Systems (GNSS). Dessa effekter kan kallas medelstora resande jonosfäriska störningar (MS-TID) vid mellanliggande latitudområden och polarkapslar på områden med hög latitud. De jonosfäriska variationerna har olika mönster för varje region och tid. De statistiska måtten på den jonosfäriska variationen analyseras presenterade som tidsfunktioner i halva solcykeln, årssäsong och tid på dygnet för fyra geografiska platser i Sverige. Genom att bearbeta uppnådda GPS-data från en 7-årsperiod, 2013-2020, från SWEPOS, utfördes karaktäriseringen av den jonoshperiska variationen. Det har visat sig att den jonosfäriska variationen är större för Norra Norrland -regionen under solminimum. Under solens maximala beror variationen dock på årstiderna men hög variation tycks förekomma mest i Svealandsregionen. För de mer norra regionerna (Norra och Södra Norrland) är den jonosfäriska variationen större under natten än på dagtid, medan för de mer sydliga regionerna (Svealand och Götaland) är variationen större under dagtid. Vid maximal sol är variationen högre under månaderna mars, maj, september och oktober och mindre i juni, juli och augusti. För jonosfärens variationsprognos föreslås en modell baserad på Recurrent Neural Network (RNN) som kallas Long Short-Term Memory (LSTM). De inställda hyperparametrarna för LSTM testas med avseende på förutsägelsens noggrannhet genom att jämföra de förutsagda värdena med de uppmätta värdena. Det har visat sig att LSTM kan ge förutsägelsesresultaten med mer än 90% noggrannhet när man använder 1-6 timmars inmatningsdata och siktar på 10-35 minuters utdata. Längre varaktighet för in- och utgång resulterar i lägre noggrannhet för de förutsagda värdena.

<p>Two coding schemes based on polar codes are proposed for the multiple description (MD) problem. The first scheme is an adaptation of the one developed by \c{S}a\c{s}o\u{g}lu {\em et al.} for the multiple access channel to the MD setting. Specifically, it is shown that the scheme is able to achieve certain rate pairs on the dominant line of the achievable rate region determined by El Gamal and Cover (EGC) when the associated auxiliary random variables have different prime alphabet sizes. Different from polar coding for the multiple access channel considered by \c{S}a\c{s}o\u{g}lu {\em et al.}, the auxiliary random variables in the MD problem can be dependent, and their alphabet sizes play an unexpected important role in the construction. The second scheme is based on the idea of rate splitting. We show that it can achieve the entire EGC rate region. The effectiveness of the proposed polar coding schemes is verified by the experimental results.</p> / Master of Applied Science (MASc)

Polar codes, introduced by Arikan in 2009, have attracted considerable interest as an asymptotically capacity-achieving code with sufficient performance advantages to merit inclusion in the 5G standard. Polar codes are constructed directly from an explicit model of the communication channel, so their performance is dependent on a detailed understanding of the transmission environment. We partially remove a basic assumption in coding theory that channels are identical and independent by extending polar codes to several types of channels with memory, including periodic Markov processes and Information Regular processes. In addition, we consider modifications to the polar code construction so that the inclusion of a shared secret in the frozen set naturally produces encryption via one-time pad. We describe one such modification in terms of the achievable frozen sets which are compatible with the polar code automorphism group. We then provide a partial characterization of these frozen sets using an explicit construction for the Linear Extension Diameter of channel entropies. / Doctor of Philosophy / Efficient, reliable communication has become an essential component of modern society. Error-correcting codes allow for the use of redundant symbols to fix errors in transmission. While it has long been known that communication channels have an inherent capacity describing the optimal redundancy required for reliable transmission, explicit constructions which achieve this capacity have proved elusive. Our focus is the recently discovered family of polar codes, which are known to be asymptotically capacity-achieving. Polar codes also perform well enough in practice to merit inclusion in the 5G wireless standard shortly after their creation. The polarization process uses an explicit model of the channel and a recursive construction to concentrate errors in a few symbols (called the frozen set), which are then simply ignored. This reliance on an explicit channel model is problematic due to a long-standing assumption in coding theory that the probability of error in each symbol is identical and independent. We extend existing results to explore persistent sources of interference modelling environments such as nearby power lines or prolonged outages. While polar codes behave quite well in these new settings, some forms of memory can only be overcome using very long codewords. We next explore an application relating to secure communication, where messages must be recovered by a legitimate receiver but not by an eavesdropper. Polar codes behave quite well in this environment as well, as we can separately compute which symbols can be recovered by each party and use only those with the desired properties. We extend a recent result which proposes the use of a shared secret in the code construction to further complicate recovery by an eavesdropper. We consider several modifications to the construction of polar codes which allow the shared secret to be used for encryption in addition to the existing information theoretic use. We discover that this task is closely related to the unsolved problem of determining which symbols are in the frozen set for a particular channel. We conclude with partial results to this problem, including two choices of frozen set which are, in some sense, maximally separated.