The research project describes the key mission and systems engineering trade-offs involved in the end-to-end design of an orbiting mission to the Moon, using a "Smaller, Faster, Cheaper" mission approach. This approach is extended to enable the design of a new payload - within the management, cost, schedule, and physical constraints - of the low cost lunar orbiter mission. The payload is designed to image the Moon's permanently dark regions that are believed to contain water ice. To determine the best cost reduction management and engineering approach, the principles for reducing space mission cost are examined and planetary missions are assessed in terms of cost and risk drivers. 'Interplanetary' trajectories and attaining orbit around another body are shown to be the major risk areas encountered by traditional planetary missions. In addition to this, programme management is highlighted as an emerging high risk area for smaller, faster cheaper planetary missions. The preliminary mission design, covering lunar transfer, spacecraft and ground station is described. A 400 kg, three-axis stabilised, lunar orbiter, capable of delivering 20 kg of payload into a low lunar polar orbit is designed. The ground segment comprises one (possibly two) low cost ground stations, linked via the Internet. Images, raw data and telemetry can also be accessed via the Internet. The design-to-launch timeframe spans three years and the total mission cost target of $20 Million is met. The spacecraft is compatible with a range of existing lunar payloads, but the prime mission requirement will be to return images of the Moon's permanently dark craters for the first time. In order to design a low cost payload for imaging the Moon's permanently dark regions, the areas likely to contain the water ice are first characterised. The best and worst case lighting conditions for imaging are then calculated for these regions. The amount of light reaching a crater floor is a function of the crater depth-diameter ratio, solar irradiance incidence angle and local topography. The limiting case is shown to be imaging under starlight illumination only, which is modelled and estimated between 5 to 10µW/m2 over the 350 to 900 nm spectral band. These ultra-low light level conditions have led to identification and evaluation of several solutions in terms of both signal-tonoise ratio performance and development within the constraints of the smaller, faster, cheaper programme. This is achieved using a charge coupled device (CCD) camera employing a commercial sensor and optics. Large format Charge Injection Devices and Complimentary Metal Oxide Semiconductors (Active Pixel Devices) were identified as promising emerging technologies. The baseline low light level imager solution is a CCD array operated in Time Delay Integration mode in order to provide optical images from areas within permanent shadow. An intensified CCD offers a back up solution. The research demonstrates that a low cost lunar mission is technically feasible and additionally, that it is possible to meet a specific (if modest) application target through `smaller, faster, cheaper' payload design. It provides an approach that meets key challenges of planetary exploration at very low cost that can potentially be applied to other near Earth targets.

Project Upsilon is a proposed NASA Flagship Class, Uranus Orbiter and Probe mission concept to investigate Uranus' planetary magnetic field and atmosphere. Three spacecraft - the Upsilon-0 Propulsion Module, the Upsilon-1 Science Orbiter, and the Upsilon-2 Atmosphere Probe - shall be implemented to meet needs, goals, and objectives as stated by the NASA Solar System Planetary Science Decadal Survey 2013-2022. Upsilon-0 shall be expended in order to complete orbital capture about Uranus. Upsilon-1 shall study Uranus' planetary magnetic field, obtaining real-time measurements for nominally 20 months within the first two years of arrival; and for as long as possible after the first two years, as part of an extended science mission. Upsilon-2 shall be descended into Uranus' cloud tops to obtain physical data and imagery well into the atmosphere's depths. Chemical propulsion is employed in place of solar-electric propulsion, with regard to the interplanetary system-level trade tree. The interplanetary trajectory requires a single un-powered flyby of Jupiter, selected among several flyby node configurations. The science orbit produces nearly repeating latitude-longitude tracks over a rotating Uranus. The statistical estimation method combines an orbit determination model with respect to Uranus' flattening, and a simple magnetic dipole model for field line modeling. A 7-year period is allotted for the technology research and development, and the testing and verification stages of the project life cycle; the interplanetary journey to Uranus requires 21 years; and the nominal in-situ operation lifetime is 2 years. The Project Upsilon spacecraft launch in 2021 to "revolutionize our understanding of ice giant properties and processes, yielding significant insight into their evolutionary history"; contributing to the Planetary Science Decadal Survey's, and NASA's, key planetary science and deep space exploration visions. / text

As an orbiter cruising to Jupiter will encounter different plasma environments, variety of spacecraft surface charging is expected. This surface potential can lead to inaccurate and wrong in-situ plasma measurements of on-board sensors, which explain the interest in simulating the charging.In this thesis the spacecraft-plasma interactions for a future mission to Jupiter are modelled with the help of the Spacecraft Plasma Interaction System, taking the case of a Jupiter Ganymede Orbiter (JGO) and a Jupiter Europa Orbiter (JEO) as an archetype for a future mission.It is shown that in solar wind at Earth and Jupiter, spacecraft potentials of about 8 V for the JEO, and 10 V to 11 V for the JGO are expected. Furthermore, at a distance of 15 Jupiter radii from Jupiter, the JGO is expected to charge to an electric potential of 2 V, except in the planetary shadow, where it will charge to a high negative potential of -40 V. Moreover, close to the orbit of Callisto, JGO will charge to 12 V in the sun and to 4.6 V in eclipse, due to a high secondary electron emission yield. / <p>Validerat; 20120115 (anonymous)</p>

The context of this study is the increasing need for public transport as issues over high private vehicle usage are becoming increasingly obvious. Public transport services need to compete with private transport to improve patronage, and issues with reliability need to be addressed. Bus bunching affects reliability through disruptions to the scheduled headways. The purpose of this study was to collect and analyse data to compare how travel time and dwell time vary, to explore the variation of key variables, and to better understand the sources of these variations. The Orbiter bus service in Christchurch was used as a case study, as it is particularly vulnerable to bus bunching. The dwell time was found to be more variable than travel time. It appeared the Canterbury earthquake had significantly reduced the average speeds for the Orbiter service. In 1964, Newell and Potts described a basic bus bunching theory, which was used as the basis for an Excel bus bunching model. This model allows input variables to vary stochastically. Random values were generated from four specified distributions derived from manually collected data, allowing variance across all bus platforms and buses. However the complexity resulted in stability and difficulty in achieving convergence, so the model was run in single Monte Carlo simulations. The outputs were realistic and showed a higher degree of bunching behaviour than previous models. The model demonstrated bunching phenomena that had not been observed in previous models, including spontaneously un-pairing, overtaking of buses delayed at platforms, and odd-numbered bunches of three buses. Furthermore, the study identified areas of further research for data collection and model development.

This thesis presents new information about the global megaregolith of the Moon, using 2059 craters (5 to 50 km diameter) as natural probes. Iron (FeO) and titanium (TiO2) concentrations were obtained from crater ejecta blanket data over an area between 600 North to 600 South latitude derived from the 1994 Clementine mission. The average iron and titanium weight percentages for lunar crater ejecta were calculated using the US Geological Survey's ISIS software, and used to determine the variation with depth of iron (FeO) and titanium (TiO2) in the highlands, mare areas and the South Pole Aitken basin. In addition, megaregolith compositional Iron (FeO) and Titanium (TiO2) Maps and compositional Province Maps were generated, and studied in detail. The Lunar Megaregolith Iron Province Map divides the Highland areas into 2 distinct provinces of low-iron Highland I (0-3.7 FeO weight percentage) and low-medium level iron Highland II (3.8-6.4%), and the Mare and South Pole Aitken Basin each into 3 distinct provinces (6.5-9.7%, 9.8-13.6%, and 13.7-18.3%). Similarly, a Titanium Megaregolith Province Map divides the Moon globally into 5 provinces based on weight percentages of TiO2. A new finding is the Highland II Province of elevated iron concentration which surrounds basins. These elevated iron levels may be explained in terms of an "Intrusion Model". In this model, basin formation fractures the surrounding anorthositic bedrock, and the middle level anorthositic crust allows mafic (basaltic?) magma to intrude. This intrusion into the megaregolith is in the form of sills and dykes from deep mafic sources but generally does not intrude into the surface regolith. In some places however, the mafic (basaltic?) lava may have extruded onto the surface, such as near Crater 846 (15.6N 92.2W). The megaregolith, which consists of large volume breccia, would have voids and vacancies in this structure into which mafic or basaltic material could intrude. "Islands" of Highland I Province material surrounded by Highland II Province indicate this intrusion was non-uniform. Another possible explanation for the Highland II Province iron levels comes from the "Thrust Block" model, where deep mafic material has been broken into large blocks by the basin-forming events, and "thrusted" or uplifted to displace most of the overlying anorthosite bedrock, thereby mechanically mixing with the megaregolith to provide the additional iron input. However, this does entirely fit comfortably with the data in this study. A third explanation for the Highland II Province arises from the "Basin Impact Ejecta Model" such as the Imbrium Impact described by Haskin (1998). The Basin Impact Ejecta model describes the effect of basin impacts around 4.0 billion to 3.8 billion years ago in the Moon's history (Ryder, 1990; Taylor, 2001)). This model implies that basin material was ejected and deposited on a global or similar scale. However, the results of this study place severe limitations on the feasibility of the "Basin Impact Ejecta" model to explain any significant mafic input from such ejecta in forming the Highland II megaregolith material. These Province Maps provide a new dimension to the study of the Moon's crustal development and reveal a highly complex history, providing a basis for future study.

As part of the ExoMars space programme, the 2016 Trace Gas Orbiter mission was announced. The Martian Atmospheric Trace Molecule Occultation Spectrometer (MATMOS) was a proposed Fourier transform spectrometer and solar imager concept pair that would provide for trace gas detection and aerosol observation of the Martian atmosphere. Martian aerosols – namely CO2 crystals, water-ice crystals, and dust – have been observed during past missions; however, observations have failed to fully characterize their physical and optical properties. This thesis presents an analysis of the ability of the proposed imager to determine the pointing of the spacecraft independent of the spectrometer. Furthermore, proof of concept is presenting showing the ability to, in laboratory conditions, characterize the precision and stability of the imager. Finally, window regions in the transmittance spectrum of the Martian atmosphere are determined simulating the Martian atmosphere and viewing geometry.

In this paper a search routine in MATLAB was developed in order to find and analyze oblique whistler waves in the data from the ESA and NASA spacecraft Solar Orbiter. Oblique whistler waves are a type of plasma wave which propagate at an angle with respect to the background magnetic field. They are efficient at scattering electrons in the solar wind but their role in interplanetary coronal mass ejections (ICMEs) is yet unknown. Magnetic field data from 1-31st of June 2022, as well as the 24th and 27-28th of January 2022 was examined. The search routine found six whistler waves in June and 12 for the dates in January. Among these, all found whistler waves were found in the sheath region of the ICMEs, and all had a plasma beta &gt; 1. However due to instrumental artefacts the values of θk were found to be smaller than detected by the search routine, indicating less obliqueness than first expected. Some of the whistler waves seemed to have an obliqueness that changed with time and the bandwidth of the waves varied among the identified.

This study researched the history of Space Shuttle Reusable Surface Insulation which was designed and developed for use on the United States Orbiter fleet to protect from the high heating experienced during reentry through Earth's atmosphere. Specifically the tile system which is attached to the structure by the means of an RTV adhesive has experienced situations where the bonds are identified as subnominal. The history of these subnominal conditions is presented along with a recent identification of a subnominal bond between the Strain Isolation Pad and the tile substrate itself. Tests were run to identify the cause of these subnominal conditions and also to show how these conditions were proved to be acceptable for flight. The study also goes into cases that could be used to identify subnominal conditions on tile as a non-destructive test prior to flight. Several options of non-destructive testing were identified and recommendations are given for future research into this topic. A recent topic is also discussed in the instance where gap fillers were identified during the STS-114 mission that did not properly adhere to the substrate. The gap fillers were found protruding past the Outer Mold Line of the vehicle which required an unprecedented spacewalk to remove them to allow for a safe reentry through the atmosphere.

No description available.

La transformada de Abel es una técnica de inversión usada frecuentemente en radio ocultaciones (RO) que, en el contexto ionosférico, permite deducir densidades electrónicas a partir de datos de STEC (Slant Total Electron Content) derivados a partir de observaciones de la fase portadora. Esta técnica está basada en medidas precisas en doble frecuencia de fase portadora ( banda L) de un receptor GPS a bordo de un satélite de órbita baja (Low Earth Orbit -LEO-) rastreando un satélite GPS detrás del limbo de la tierra. Al combinar tales medidas con la información de posiciones y velocidades de los satélites GPS y LEO, es posible deducir el cambio en el camino de la señal debido a la presencia de la atmósfera y, consecuentemene, convertirlo en ángulos de curvatura (bending angles). A partir de ellos, información sobre el índice de refracción vertical puede ser obtenida a través de técnicas de inversión, y transformarlo en perfiles verticales de densidad electrónica y/o perfiles de atmósfera neutra. Una de las hipótesis básicas de la inversión clásica es suponer que el campo de densidades electrónicas tiene simetría esférica en la vecindad de una ocultación. Sin embargo, a la práctica, la huella de una ocultación generalmente cubre regiones de miles de km que puede presentar variabilidad ionosférica importante; por lo cuál, la hipótesis de simetría esférica no puede ser garantizada. De hecho, las inhomogeneidades de la densidad electrónica en la dirección veritcal para una ocultación dada son una de las principales causas de error cuando se usa la inversión de Abel inversion. Para corregir el error debido a la hipótesis de simetría esférica, se introduce el concepto de separabilidad. Ello implica que la densidad electrónica puede ser expresada como una combinación de datos de Vertical Total Electron Content (VTEC) derivados externamente, los cuales asumen la dependencia horizontal de la densidad, y una función de forma, que a su vez asume la dependencia en altura que es común a todas las observaciones para una ocultación dada. Nótese que el espesor de capa permanece constante cerca de la región de la ocultación debido a la hipótesis de separabilidad en vez de la densidad, como ocurriría en el caso de usar simetría esférica. Esta técnica fue aplicada exitosamente a la combinación lineal de fases de GPS L1 y L2, , LI= L1-2, la cuál proporcionar un observable libre de geometría que depende sólo del retraso ionosférico, la ambigüedad de fase, biases instrumentales y wind-up. Los resultados presentaban una mejora del 40% en RMS al comparar frecuencias del pico de la capa F2 con datos de ionosonda respecto la inversión clásica de Abel. Sin embargo, la potencial influencia de la diferencia de caminos ópticos entre L1 y L2 fue despreciada. Esta tesis doctoral muestra que ello no es un problema para la inversión a alturas ionosféricas. Una alternativa para la inversión de perfiles que evita esta desventaja es usar la curvatura de la señal como dato principal. La implementación de la separabilidad para ángulos de curvatura no es inmediata y ha sido uno de los objetivos de esta tesis. En este sentido, el principio de la separabilidad ha sido aplicado a los ángulos de curvatura de L1 en vez de la la combinación LI como en trabajos anteriores. Además, trabajando con ángulos de curvatura, la separabilidad puede ser también trasladada a la obtención de perfiles troposféricos. Varias aproximaciones para obtener la contribución de las partes altas de la ionosfera han sido también estudiadas, aparte del hecho de simplemente prescindir de esta contribución. Se ha usado un modelo climatológico, una extrapolación exponencial y el hecho de considerar las implicaciones de usar separabilidad. También se ha propuesto una manera para obtener funciones de mapeo (mapping functions) deducidas a partir de perfiles RO. Sin embargo, trabajando sólo con datos derivados únicamente de RO, se está sistematicamente despreciando la contribución de la protonosfera al TEC. Con la propuesta inicial de función de mapeo sólo la contribución ionosférica es tenida en cuenta. La solución ideal para aplicaciones de datos de tierra GNSS sería usar un modelo de dos capas, una para modelar la ionosfera y otra para la protonosfera, o alternativamente, si se quisiera alta resolución tomográfica, combinar observaciones RO y con elevación positiva de LEOs con datos de tierra. Se ha probado que modelando con dos capas, los resultados que se habían obtenido con el análisis de datos RO han podido ser validados. La conclusión más importante es que la proporción entre la contribución ionosférica y protonosférica es el parámetro que explica la localización de las alturas efectivas. / La transformada d’Abel és una tècnica emprada freqüentment en radio ocultacions (RO) que, en el context ionosfèric, permet deduir densitats electròniques a partir de dades de STEC (Slant Total Electron Content) derivats a partir d’observacions de la fase portadora. Aquesta tècnica està basada en mesures precises en doble freqüència de fase portadora (banda L) d’un receptor GPS a bord d’un satèl·lit d’òrbita baixa (Low Earth Orbit-LEO-) rastrejant un satèl·lit GPS darrere del limb de la terra. En combinar les dites mesures amb la informació de posicions i velocitats dels satèl·lits GPS i LEO, és possible deduir el canvi en el camí del senyal degut a la presència de l’atmosfera i, conseqüentment, convertir-lo en angles de curvatura (bending angles). A partir d’ells, informació sobre l’índex de refracció vertical pot ser obtinguda mitjançant tècniques d’inversió i transformar-lo en perfils verticals de densitat electrònica i/o perfils d’atmosfera neutra. Una de les hipòtesis bàsiques de la inversió clàssica és suposar que el camp de densitats electròniques té simetria esfèrica en el veïnatge d’una ocultació. Tanmateix, a la pràctica, la petjada d’una ocultació generalment cobreix regions de milers de quilòmetres que pot presentar variabilitat ionosfèrica important; per la qual cosa, la hipòtesi de simetria esfèrica no pot ser garantida. De fet, les inhomogeneitats de la densitat electrònica en la direcció vertical per a una ocultació donada són una de les principals causes d’error quan es fa servir la inversió d’Abel. Per a corregir l’error a causa de la hipòtesi de simetria esfèrica, s’introdueix el concepte de separabilitat. Això implica que la densitat electrònica pot ser expressada com una combinació de dades de Vertical Total Electron Content (VTEC) derivats externament, els quals assumeixen la dependència horitzontal de la densitat, i una funció de forma, la qual alhora assumeix la dependència en altura que és comuna a totes les observacions per a una ocultació donada. Cal notar que l’espessor de capa roman constant a prop de la regió de l’ocultació a causa de la hipòtesi de separabilitat en comptes de la densitat, tal i com succeiria en el cas de fer servir simetria esfèrica. Aquesta tècnica fou aplicada amb èxit a la combinació lineal de fases de GPS L1 i L2, LI=L1-2, la qual proporciona un observable lliure de geometria que depèn només del retard ionosfèric, l’ambigüitat de fase, biases instrumentals i wind-up. Els resultats presenten una millora del 40% en RMS en comparar freqüències del pic de la capa F2 amb dades de ionosonda respecte la inversió clàssica d’Abel. No obstant, la potencial influència de la diferència de camins òptics entre L1 i L2 fou menyspreada. Aquesta tesi doctoral mostra que això no és pas un problema per a la inversió a altures ionosfèriques. Una alternativa per a la inversió de perfils que evita aquesta desavantatge és emprar la curvatura del senyal com a dada principal. La implementació de la separabilitat per a angles de curvatura no és immediata i ha estat un dels objectius d’aquesta tesi. En aquest sentit, el principi de la separabilitat ha esta aplicat als angles de curvatura de L1 en comptes de la combinació LI com en treballs anterior. A més, treballant amb angles de curvatura, la separabilitat pot ser també traslladada a l’obtenció de perfils troposfèrics. Varies aproximacions per a obtenir la contribució de les parts altes de la ionosfera han estat també estudiades, apart del fet de prescindir simplement d’aquesta contribució. S’ha fet servir un model climatològic, una extrapolació exponencial i el fet de considera les implicacions d’usar separabilitat. També s’ha proposat una manera pera obtenir funcions de mapeo (mapping functions) deduïdes a partir de perfils RO. Tanmateix, treballant només amb dades derivades únicament de RO, s’està menyspreant sistemàticament la contribució de la protonosfera al TEC. Amb la proposta inicial de funció de mapeo només tenim en compte la contribució ionosfèrica. La solució ideal per a aplicacions de dades de terra GNSS seria fer servir un model de dues capes, una per a modelar la ionosfera i una altra per la protonosfera, o alternativament, si es volgués alta resolució tomogràfica, combinar observacions RO i amb elevació positiva de LEOs amb dades de terra. S’ha provat que modelant amb dues capes, els resultats obtinguts amb l’anàlisi de dades RO han pogut estar validats. La conclusió més important és que la proporció entre la contribució ionosfèrica i protonosfèrica és el paràmetre que explica la localització de les altures efectives. / The Abel transform is a frequently used radio occultation (RO) inversion technique which, in the ionospheric context, allows retrieving electron densities as a function of height from STEC (Slant Total Electron Content) measurements derived from carrier phase observations. The GPS RO technique is based on precise carrier dual-frequency phase measurements (L-band) of a GPS receiver onboard a Low Earth Orbit satellite (LEO) tracking a rising or setting GPS satellite behind the limb of the earth. When combining such measurements with the information from the positions and velocities of GPS and LEO satellites, it is possible to derive the phase path change due to the atmosphere during an occultation event which subsequently can be converted into bending angles. From these, information about the vertical refraction index can be obtained by means of inversion techniques, which can then be converted into ionospheric vertical electron density profiles and/or neutral atmospheric profiles. One of the basic assumptions in the classical approach is to assume the spherical symmetry of the electron density field in the vicinity of an occultation. However, in practice, the footprint of an occultation generally covers wide regions of thousands of kilometres in length that may show significant ionospheric variability; therefore this hypothesis cannot be guaranteed. Indeed, inhomogeneous electron density in the horizontal direction for a given occultation is believed to be one of the main sources of error when using the Abel inversion. In order to correct the error due to the spherical symmetry assumption, the separability concept is introduced and applied. This implies that the electron density can be expressed by a combination of externally derived Vertical Total Electron Content (VTEC) data, which assumes the horizontal dependency, and a shape function, which in turn assumes the height dependency that is common to all the observations for a given occultation. Note that the slab thickness remains constant near the occultation due to the separability hypothesis instead of the density as is the case of the spherical symmetry. This technique was successfully applied to the linear combination of the GPS carrier phases L1 and L2, , LI= L1-2 which is a geometric free observable that depends only on the ionospheric delay, phase ambiguity, instrumental bias and wind-up. The result was an improvement of about 40% in RMS when comparing frequencies of the F2 layer peak with ionosonde data and the classical Abel inversion. The main advantage of such developed technique is its simple computation. Nevertheless, the potential influence of the different signal paths between L1 and L2 was neglected. Regarding this aspect, this Ph.D. dissertation shows that is not a problem for inversion at ionospheric heights. An alternative to inverting the profile, which overcomes this disadvantage, is to use the bending angle of the signal as the main input data. The implementation of separability when using the bending angle is not immediate and was, actually, one of the goals of this thesis. In this sense, the separability approach has been applied to measured L1 bending angle, instead of LI combination as reported in previous work. Additionally, this approach could also be translated to tropospheric profile retrievals. Several approaches to account for the upper ionospheric contribution have been also tackled, apart from the fact of neglecting such contribution: a climatological model, an exponential extrapolation and condisering the nature of the separability concept. it has been proposed a way to obtain mapping functions derived from RO profiles. Such mapping functions can be easily derived from usual ionospheric parameters. For the contribution of this part of the ionosphere, it has been shown that it is capable to account for the total electron content (TEC). However, by working solely with RO derived data, we are systematically neglecting the contribution of the protonosphere to the total electron content. With the initial proposed mapping function based on the analysis of effective heights derived from RO, only the ionospheric contribution is accounted for. The ideal solution for ground-based GNSS data applications would be to use a two-layer model, one to model the ionosphere and another one for the protonosphere, or alternatively, if we are looking for high tomographic resolution, to combine RO and topside LEO observations with ground data. It has been shown that by modelling in such way, the results that were obtained with RO data analysis can be validated. The most important conclusion is that the ratio between ionospheric and protonospheric contribution is the driver for the location of the effective heights.