The thermosphere is the region between approximately 80 km and 320 or more km above the earth's surface. While many people consider this elevation to be space rather than atmosphere, there is a small quantity of gasses in this region. The behavior of these gasses influences the orbits of satellites, including the International Space Station, causes space weather events, and influences the weather closer to the surface of the earth. Due to the location and characteristics of the thermosphere, even basic properties such as temperature are very difficult to measure. High spatial and temporal resolution data on temperatures and winds in the thermosphere are needed by both the space weather and earth climate modeling communities. To address this need, Space Dynamics Laboratory (SDL) started the Profiling Oxygen Emissions of the Thermosphere (POET) program. POET consists of a series of sensors designed to fly on sounding rockets, CubeSats, or larger platforms, such as IridiumNEXT SensorPODS. While each sensor design is different, they all use characteristics of oxygen optical emissions to measure space weather properties. The POET program builds upon the work of the RAIDS, Odin, and UARS programs. Our intention is to dramatically reduce the costs of building, launching, and operating spectrometers in space, thus allowing for more sensors to be in operation. Continuous long-term data from multiple sensors is necessary to understand the underlying physics required to accurately model and predict weather in the thermosphere. While previous spectrometers have been built to measure winds and temperatures in the thermosphere, they have all been large and expensive. The POET sensors use new focal plane technology and optical designs to overcome these obstacles. This thesis focuses on the testing and calibration of the two POET sensors: the Oxygen Profiling of the Atmospheric Limb (OPAL) temperature sensor and the Split-field Etalon Doppler Imager (SEDI) wind sensor

Cube Satellite (CubeSat) launches have been on the rise since its first launch in2003. This popularity is mainly due to faster design process and lower launch costs.However, most CubeSats are launched into Low Earth Orbits (LEOs), with nomissions to Geostationary Transfer Orbits (GTOs). However, many mission areplanned for the next half-decade.A major challenge to launch a CubeSat into a GTO is the thermal environmentof the higher altitude orbits. These orbits are significantly colder due to reducedheating from Earth’s planetary and albedo radiations, and a possibility for longereclipses due to the eccentricities of GTOs.A thermal investigation of the thermal environment was done using the Foresailmissions as examples, as the missions currently are set to fly the first missions toPolar LEO. The trajectories for the second Foresail mission are being evaluated,with the GTO being a strong contender. This thermal investigation is done througha comparative study of the two missions. The thermal effects of a few missionspecific scenarios were also evaluated.This provided a holistic thermal design of the first Foresail mission. A region specificthermal solution for the battery was analyzed. The various mission scenarios andtheir comparisons with the LEO mission, also formed a basis of the feasibility ofvarious situations on the second mission. Moreover, the results, in part assessedthe thermally feasibility to launch a 3U CubeSat into a GTO.The results showed GTOs show larger magnitude of variation of thermal loads ascompared to LEOs. However, these variations are more gradual due to the largerorbital periods. A 3U CubeSat can be launched into both, the LEO and GTOenvironments with passive thermal control. The properties of the thermal coatsvary slightly. However, it is not possible to passively control the CubeSat if theeclipse occurred at the aphelion of the orbit.

While dual-frequency GPS receivers have been used in space for more than two decades, the size, power, and cost of this technology is an important driver for future space missions. The growing availability of launch opportunities for very small satellites known as nanosatellites and CubeSats raises the possibility of more affordable access to space measurements if the observation quality is sufficient to support the user's needs. This thesis presents the initial development and testing of the Fast, Orbital, TEC, Observables, and Navigation (FOTON) receiver: a small, reconfigurable, dual-frequency, space-based GPS receiver. Originally developed as a science-grade software receiver for monitoring ionospheric scintillation and total electron content (TEC), this receiver was designed to provide high-quality GPS signal observations. The original receiver hardware was miniaturized and the software has been adapted for low earth orbit (LEO) operations. FOTON now fits within a 0.5U CubeSat form factor (8.3 x 9.6 x 3.8 cm), weighs 326 g, and consumes 4.5 W of instantaneous power, which can be reduced to <1 W orbit average power with on-off duty cycling. The receiver has been designed with commercial parts to keep manufacturing costs low. Significant testing of FOTON has been performed with live signals and with signals generated by a Spirent GPS signal simulator. Initial terrestrial tests demonstrate behavioral consistency with the original heritage high-performance receiver. Several LEO simulations are presented, demonstrating FOTON's single-frequency and dual-frequency-enhanced positioning down to 0.5 m and 1.5 m, respectively, which can be improved using Kalman filter based POD. FOTON's potential for GPS radio occultation observation is also demonstrated. In addition, its acquisition and reacquisition performance is presented; on average, FOTON's time to first fix is approximately 45 seconds. Finally, navigation in geostationary orbit (GEO), a challenging application for space-based GPS receivers, is demonstrated. Extensive testing demonstrates that FOTON is a robust, versatile, high-precision dual-frequency space receiver. Its low cost, size, weight, and power requirements are key enablers for future small-satellite missions. / text

This research outlines a low-cost, low-power, arc-minute accurate star tracker that is designed for use on a CubeSat. The device is being developed at the University of Texas at Austin for use on two different 3-unit CubeSat missions. The hardware consists of commercial off-the-shelf parts designed for use in industrial machine vision systems and employs a 1024x768 grey-scale charge coupled device (CCD) sensor. The software includes the three standard steps in star tracking: centroiding, star identification, and attitude determination. Centroiding algorithms were developed in-house. The star identification code was adapted from the voting method developed by Kolomenkin, et al. Attitude determination was performed using Markley's singular value decomposition method. The star tracker was then tested with internal simulated star-fields. The resulting accuracy was less than an arcminute. It was concluded that this system is a viable option for CubeSats looking to improve their attitude determination. On-orbit demonstration of the system is planned when the star tracker flies on the planned CubeSat missions in 2013 or later. Further testing with external simulated star fields and night sky tests are also planned. / text

The University of Texas at Austin (UT-Austin) Satellite Design Lab (SDL) is currently designing two 3U CubeSat spacecraft – Bevo-2 and ARMADILLO – which serve as the foundation for the design reusability and cost analysis of this thesis. The thesis explores the reasons why a small satellite would want to incorporate a reusable design and the processes needed in order for this reusable design to be implemented for future projects. Design and process reusability reduces the total cost of the spacecraft, as future projects need only alter the components or documents necessary in order to create a new mission. The thesis also details a grassroots approach to determining the total cost of a 3U CubeSat satellite development project and highlights the costs which may be considered non-recurring and recurring in order to show the financial benefit of reusability. The thesis then compares these results to typical models used for cost analysis in industry applications. The cost analysis determines that there is a crucial gap in the cost estimating of nanosatellites which may be seen by comparing two widely-used cost models, the Small Satellite Cost Model (SSCM <100 kg) and the NASA/Air Force Cost Model (NAFCOM), as they apply to a 3U CubeSat project. While each of these models provides a basic understanding of the elements which go into cost estimating, the Cost Estimating Relationships (CERs) do not have enough historical data of picosatellites and nanosatellites (<50 kg) to accurately reflect mission costs. Thus, the thesis documents a discrepancy between widely used industry spacecraft cost models and the needs of the picosatellite and nanosatellite community, specifically universities, to accurately predict their mission costs. It is recommended to develop a nanosatellite/CubeSat cost model with which university and industry developers alike can determine their mission costs during the designing, building and operational stages. Because cost models require the use of many missions to form a database, it is important to start this process now at the beginning of the nanosatellite/CubeSat boom. / text

A Command and Data Handling (C&DH) system is being developed as part of a series of CubeSat missions being built at The University of Texas at Austin’s Texas Spacecraft Laboratory (TSL). With concurrent development of four missions, and with more missions planned for the future, the C&DH team is developing a system architecture that can support many mission requirements. The presented research aims to establish itself as a reference for the development of the C&DH system architecture so that it can be reused for future university missions. The C&DH system is designed using a centralized architecture with one main flight computer controlling the actions and the state of the satellite. A Commercial Off-The-Shelf (COTS) system-on-module embedded computer running a Linux environment hosted on a custom interface board is used as the platform for the mission software. This design choice and the implementation details of the flight software are described in detail in this report. The design of the flight software and the associated hardware are integral components of the spacecraft for the current missions in the TSL which, when flown, will be some of the most operationally complex CubeSat missions attempted to date. / text

Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018. / This research report discusses feasible designs of conformal antennas that provide a proof of concept for the French South African Institute of Technology’s future needs. The design is to be used in forthcoming space missions and the intention is to mount the antenna on the surface of a spacecraft. Hence, a low profile is mandatory along with good circular polarisation radiation characteristics. Microstrip patch antennas have been chosen for this purpose simply because they have low profile and conform to most structures, thus fulfilling the requirements stated above. All the designs that are featured in this thesis were modelled and validated using the electromagnetic simulation software FEKO and prototypes were built and tested. The simulations and measured results are supplemented by theory. Sometimes it can be challenging to design and develop an antenna that fulfils the required performance goals given the size and weight restrictions that are specified for nano-satellite technology. Therefore, the first phase of this project finds a good balance between the criteria set for CubeSat platforms and antenna performance. The second phase is validation. Single patch antennas and a sequential rotated patch array were designed, built and tested. The sequential rotated patch array offers considerable improvements in performance when compared to single patch antennas. For instance, the 3 dB axial ratio bandwidth increased to 9.6 % from 2 % when a sequential rotated array was used. The CubeSat normally flies in the inclined regions of the low Earth orbit (LEO). This area has high-energy auroral electron fluxes, in which the high-density electrons build up on ungrounded surfaces of spacecraft and cause discharge arcing. The discharge can affect the satellite operation and, in the worst case, cause permanent damage to the components. A mitigation technique by means of a bleeding path provides a quick route to ground and the space-qualified material that is used will ensure that the antenna is robust enough to survive this.

By shining a precisely tuned laser through an atomic vapor, we can determine local mag- netic field strength in scalar form and in a way that is not affected by temperature changes. This technology has been used in space many times before on missions flown by NASA and ESA, such as SWARM, Øersted, and CHAMP to calibrate accompanying vector mag- netometers which are subject to offsets caused by temperature changes. The device we constructed is a small, low-cost application of this scientific principle and opens up new areas of scientific possibility for cubesats and the ability to define geomagnetic field struc- tures on a small (<10km) scale as part of the ANDESITE cubesat mission being developed at Boston University. Previously, magnetic sensors in orbit have been flown individually on a single spacecraft or in very small groups such as the International Sun-Earth Exporers (ISEE) and SWARM which each used three separate spacecraft. This method of analyzing the geomagnetic field cannot provide a spatial or time resolution smaller than that of the separation between magnetic field readings. This project has focused on producing a tabletop demonstra- tion of a compact sensor head which could enable measurements on unprecedented small scales. Toward this end we have accomplished the construction and preliminary testing of a compact sensor head which contains all necessary elements to function as a scalar atomic magnetometer.

Ingeniero Civil Eléctrico / Los sensores magnéticos son ampliamente utilizados siendo de gran ayuda en la navegación al ser usados como como una brújula, memorias magnéticas para ordenadores, sistemas automáticos, control de automóviles y detección. Incluso han sido determinantes en medicina mediante la medición del campo magnético del corazón, cerebro o pulmones, revelando información importante acerca de las corrientes dentro del cuerpo. Estas aplicaciones son ampliamente revisadas en la literatura actual, pero la importancia radica en que tienen el mismo centro: el magnetómetro. En el presente trabajo, un magnetómetro es parte de una misión de investigación que se desplegarán en la misión CubeSat SUCHAI 2 y 3 para mediciones in-situ de campo magnético en la magnetosfera bajo el nombre de MAG-SPEL (Magnetometer of Space and Planetary Exploration Laboratory). Este tipo de medición se realiza principalmente por medio de los magnetómetros de gama alta, tales como Search Coil o Flux Gate, que son grandes y robustos. La presente tesis tendrá un enfoque diferente: pequeña escala y sensores de poco valor para los satélites pequeños (CubeSat) solamente usando COTS (componentes comprables de manera fácil y rápida), siguiendo el trabajo realizado por Imperial College y su sensor MAGIC. En este caso los sensores son: pequeños, baratos, replicables, medianamente sensibles y de consumo moderado. Para esto se diseñó todo el sistema mediante el uso de un sensor comercial (HMC1001) y un front-end electrónico acorde para procesar la señal, utilizando las guías del magnetómetro MAGIC con la perspectiva de lograr mejoras tales como: diseño modular, cambio de rieles de voltaje, mejoras sobre el espectro de ruido y tratamiento de la señal differencial, culminando en una mejora de la sensitividad. Se realizaron pruebas para cuantificar las variables de interés, tales como corriente de polarización y consumo, para luego pasar a realizar una calibración utilizando una Helmholzt Cage y un magnetómetro de referencia para una calibración cruzada. Esta calibración se realizó en Boston University utilizando equipo especializado para tal calibración. Todo esto con el fin de demostrar que se puede lograr generar un sensor magnético competitivo basado en MAGIC. Finalmente se logró obtener un magnetómetro levemente superior en comparación al realizado por Imperial College, logrando una sensitividad de 10 50 nT cumpliendo todas las mejoras prometidas alcanzando rangos dinámicos de 45.000 nT y consumos alrededor de 1 W en funcionamiento tri axial además de cumplir con las restricciones impuestas por una misión CubeSat / Este trabajo ha sido parcialmente financiado por CONICYT/PCHA/Magíster Nacional / 2015-22150792 y por el Departamento de Postgrado y Postítulo de la Universidad de Chile

Ingeniero Civil Electricista / En el contexto de las Ciencias Aeroespaciales, surge la necesidad de disponer al alcance de universidades y otros organismos la posibilidad de realizar investigación en el área sin requerir inversiones costosas y planificaciones de largo plazo. Esta idea se concreta actualmente en el lanzamiento de pequeños satélites agrupados bajo el estándar CubeSat. El proyecto SUCHAI, del Departamento de Ingeniería Eléctrica, busca poner en órbita el primer satélite de este tipo desarrollado por una Universidad chilena. Las severas limitaciones de peso, tamaño y recursos de estos satélites impone varios desafíos para mantenerlos funcionales en su órbita. La comunicación con la estación terrestre, desde donde se envían y reciben señales, es crítica para dicho fin. Varios elementos afectan el enlace, como son la alta velocidad de traslación del satélite y el ruido introducido por fenómenos climáticos y la ionosfera. Esto lleva a la necesidad de evaluar mecanismos para minimizar la corrupción en la información transmitida, entre los cuales son de amplia aplicación los esquemas de codificación. En el contexto del proyecto SUCHAI, este trabajo tiene por objetivos evaluar estrategias de control de errores adecuadas para el entorno descrito, acotando el estudio a los esquemas de codificación algebraica, e implementar aquella que se ajuste mejor a los requisitos impuestos. La evaluación realizada abarca la simulación de algunas estrategias de codificación, bajo esquemas de modulación en frecuencia y en fase binarios cuyos resultados indican que el código convolucional reduce significativamente los errores en la transmisión. Esto motiva la implementación de un esquema convolucional en un módulo FPGA Spartan-3E de Xilinx, la que se realizó parcialmente en el software ISE. Con los logros alcanzados, se presentan desafíos de implementación completa y eficiente del código convolucional, realización de pruebas bajo condiciones más realistas a las simuladas, o la evaluación de otros esquemas de codificación y modulación bajo modelos de canal más representativos.