Matching Items (31)
Description
CubeSats can encounter a myriad of difficulties in space like cosmic rays, temperature<br/>issues, and loss of control. By creating better, more reliable software, these problems can be<br/>mitigated and increase the chance of success for the mission. This research sets out to answer the<br/>question: how do we create reliable flight software for CubeSats? by providing a concentrated<br/>list of the best flight software development practices. The CubeSat used in this research is the<br/>Deployable Optical Receiver Aperture (DORA) CubeSat, which is a 3U CubeSat that seeks to<br/>demonstrate optical communication data rates of 1 Gbps over long distances. We present an<br/>analysis over many of the flight software development practices currently in use in the industry,<br/>from industry leads NASA, and identify three key flight software development areas of focus:<br/>memory, concurrency, and error handling. Within each of these areas, the best practices were<br/>defined for how to approach the area. These practices were also developed using experience<br/>from the creation of flight software for the DORA CubeSat in order to drive the design and<br/>testing of the system. We analyze DORA’s effectiveness in the three areas of focus, as well as<br/>discuss how following the best practices identified helped to create a more reliable flight<br/>software system for the DORA CubeSat.
ContributorsHoffmann, Zachary Christian (Author) / Chavez-Echeagaray, Maria Elena (Thesis director) / Jacobs, Daniel (Committee member) / Computer Science and Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Galaxies represent a fundamental catalyst in the ``lifecycle'' of matter in the Universe, and the study of galaxy assembly and evolution provides unique insight into the physical processes governing the transformation of matter from atoms to gas to stars. With the Hubble Space Telescope, the astrophysical community is able to study the formation and evolution of galaxies, at an unrivaled spatial resolution, over more than 90% of cosmic time. Here, I present results from two complementary studies of galaxy evolution in the local and intermediate redshift Universe which used new and archival HST images. First, I use archival broad-band HST WFPC2 optical images of local (d<63 Mpc) Seyfert-type galaxies to test the observed correlation between visually-classified host galaxy dust morphology and AGN class. Using quantitative parameters for classifying galaxy morphology, I do not measure a strong correlation between the galaxy morphology and AGN class. This result could imply that the Unified Model of AGN provides a sufficient model for the observed diversity of AGN, but this result could also indicate the quantitative techniques are insufficient for characterizing the dust morphology of local galaxies. To address the latter, I develop a new automated method using an inverse unsharp masking technique coupled to Source Extractor to detect and measure dust morphology. I measure no strong trends with dust-morphology and AGN class using this method, and conclude that the Unified Model remains sufficient to explain the diversity of AGN. Second, I use new UV-optical-near IR broad-band images obtained with the HST WFC3 in the Early Release Science (ERS) program to study the evolution of massive, early-type galaxies. These galaxies were once considered to be ``red and dead'', as a class uniformly devoid of recent star formation, but observations of these galaxies in the local Universe at UV wavelengths have revealed a significant fraction (30%) of ETGs to have recently formed a small fraction (5-10%) of their stellar mass in young stars. I extend the study of recent star formation in ETGs to intermediate-redshift 0.35<1.5 with the ERS data. Comparing the mass fraction and age of young stellar populations identified in these ETGs from two-component SED analysis with the morphology of the ETG and the frequency of companions, I find that at this redshift many ETGs are likely to have experienced a minor burst of recent star formation. The mechanisms driving this recent star formation are varied, and evidence for both minor merger driven recent star formation as well as the evolution of transitioning ETGs is identified.
ContributorsRutkowski, Michael (Author) / Windhorst, Rogier A. (Thesis advisor) / Bowman, Judd (Committee member) / Butler, Nathaniel (Committee member) / Desch, Steven (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2013
Description
Using data from the Arizona Radio Observatory Submillimeter Telescope, we have studied the active, star-forming region of the R Coronae Australis molecular cloud in 12CO (2-1), 13CO (2-1), and HCO+ (3-2). We baselined and mapped the data using CLASS. It was then used to create integrated intensity, outflow, and centroid velocity maps in IDL. These clearly showed the main large outflow, and then we identified a few other possible outflows.
ContributorsBlumm, Margaret Elizabeth (Author) / Groppi, Christopher (Thesis director) / Bowman, Judd (Committee member) / Mauskopf, Philip (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor)
Created2014-05
Description
The Hydrogen Epoch of Reionization Array, HERA, is a radio telescope currently being built in South Africa that plans to observe the early universe, specifically the earliest period of star and galaxy formation. It plans to use a tool called a delay spectrum to separate signal emitted from this time from the much brighter radio foregrounds. It is the purpose of this paper to outline the method used to characterize the contamination of these delay spectra by bright emissions of radio here on Earth called radio frequency interference, RFI. The portion of the bandwidth containing the signal from the period of initial star formation was specifically examined. In order to receive usable data, the HERA commissioning team was assisted in the evaluation of the most recent data releases. On the first batch of usable data, flagging algorithms were run in order to mask all of the RFI present. A method of filling these masked values was determined, which allowed for the delay spectrum to be observed. Various methods of injecting RFI into the data were tested which portrayed the large dependence of the delay spectrum on its presence. Finally, the noise power was estimated in order to predict whether or not the limitations observed in the dynamic range were comparable to the noise floor. By examining the evolution of the delay spectrum's power as a range of noise power was introduced, there is a good amount of evidence that this limitation is in fact the noise floor. From this, we see that excision algorithms and interpolation used are capable of removing the effects of most all of the RFI contamination.
ContributorsBechtel, Shane Kirkpatrick (Author) / Bowman, Judd (Thesis director) / Jacobs, Daniel (Committee member) / Beardsley, Adam (Committee member) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
The Epoch of Reionization (EoR) is the period in the evolution of the universe during which neutral hydrogen was ionized by the first luminous sources, and is closely linked to the formation of structure in the early universe. The Hydrogen Epoch of Reionization Array (HERA) is a radio interferometer currently under construction in South Africa designed to study this era. Specifically, HERA is dedicated to studying the large-scale structure during the EoR and the preceding Cosmic Dawn by measuring the redshifted 21-cm line from neutral hydrogen. However, the 21-cm signal from the EoR is extremely faint relative to galactic and extragalactic radio foregrounds, and instrumental and environmental systematics make measuring the signal all the more difficult. Radio frequency interference (RFI) from terrestrial sources is one such systematic. In this thesis, we explore various methods of removing RFI from early science-grade HERA data and characterize the effects of different removal patterns on the final 21-cm power spectrum. In particular, we focus on the impact of masking narrowband signals, such as those characteristic of FM radio and aircraft or satellite communications, in the context of the algorithms currently used by the HERA collaboration for analysis.
ContributorsWhitler, Lily (Author) / Jacobs, Daniel (Thesis director) / Bowman, Judd (Committee member) / Beardsley, Adam (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / Department of Physics (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
I test the hypothesis that galactic magnetic fields originate from regions of dense
star formation (Dahlem et al. 2006) by comparing maps of 120-240 MHz synchrotron emission and hydrogen alpha (Hα) emission of the tidally-interacting, edge-on, barred spiral galaxy UGC 9665. Synchrotron emission traces magnetic field strength to a rough first order, while Hα emission traces recent massive star formation. UGC 9665 was selected because it was included in the LOw Frequency ARray (LOFAR) TwoMetre Sky Survey (LoTSS; Shimwell et al. (2017)) as well as the Calar Alto Legacy Integral Field Area Survey (CALIFA; Sanchez et al. (2012)). I generated vertical intensity profiles at several distances along the disk from the galactic center for synchrotron emission and Hα in order to measure how the intensity of each falls off with distance from the midplane. In addition to correlating the vertical profiles to see if there is a relationship between star formation and magnetic field strength, I fit the LOFAR vertical profiles to characteristic Gaussian and exponential functions given by Dumke et al. (1995). Fitting these equations have been shown to be good indicators of the main mode of cosmic ray transport, whether it is advection (exponential fit) or diffusion (Gaussian fit) (Heesen et al. 2016). Cosmic rays originate from supernova,
and core collapse supernovae occur in star forming regions, which also produce
advective winds, so I test the correlation between star-forming regions and advective regions as predicted by the Heesen et al. (2016) method. Similar studies should be conducted on different galaxies in the future in order to further test these hypotheses and how well LOFAR and CALIFA complement each other, which will be made possible by the full release of the LOFAR Two-Metre Sky Survey (LoTSS) (Shimwell et al. 2017).
star formation (Dahlem et al. 2006) by comparing maps of 120-240 MHz synchrotron emission and hydrogen alpha (Hα) emission of the tidally-interacting, edge-on, barred spiral galaxy UGC 9665. Synchrotron emission traces magnetic field strength to a rough first order, while Hα emission traces recent massive star formation. UGC 9665 was selected because it was included in the LOw Frequency ARray (LOFAR) TwoMetre Sky Survey (LoTSS; Shimwell et al. (2017)) as well as the Calar Alto Legacy Integral Field Area Survey (CALIFA; Sanchez et al. (2012)). I generated vertical intensity profiles at several distances along the disk from the galactic center for synchrotron emission and Hα in order to measure how the intensity of each falls off with distance from the midplane. In addition to correlating the vertical profiles to see if there is a relationship between star formation and magnetic field strength, I fit the LOFAR vertical profiles to characteristic Gaussian and exponential functions given by Dumke et al. (1995). Fitting these equations have been shown to be good indicators of the main mode of cosmic ray transport, whether it is advection (exponential fit) or diffusion (Gaussian fit) (Heesen et al. 2016). Cosmic rays originate from supernova,
and core collapse supernovae occur in star forming regions, which also produce
advective winds, so I test the correlation between star-forming regions and advective regions as predicted by the Heesen et al. (2016) method. Similar studies should be conducted on different galaxies in the future in order to further test these hypotheses and how well LOFAR and CALIFA complement each other, which will be made possible by the full release of the LOFAR Two-Metre Sky Survey (LoTSS) (Shimwell et al. 2017).
ContributorsHuckabee, Gabriela R (Author) / Jansen, Rolf (Thesis director) / Windhorst, Rogier (Committee member) / Bowman, Judd (Committee member) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Accurate pointing is essential for any space mission with an imaging payload. The Phoenix Cubesat mission is being designed to take thermal images of major US cities from Low Earth Orbit in order to study the Urban Heat Island effect. Accurate pointing is vital to ensure mission success, so the satellite's Attitude Determination and Control System, or ADCS, must be properly tested and calibrated on the ground to ensure that it performs to its requirements. A commercial ADCS unit, the MAI-400, has been selected for this mission. The expected environmental disturbances must be characterized and modeled in order to inform planning the operations of this system. Appropriate control gains must also be selected to ensure the optimal satellite response. These gains are derived through a system model in Simulink and its response optimization tool, and these gains are then tested in a supplier provided Dynamic Simulator.
ContributorsWofford, Justin Michael (Author) / Bowman, Judd (Thesis director) / Jacobs, Daniel (Committee member) / School of Earth and Space Exploration (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Museum evaluation is an important process that aims to study an exhibit's effectiveness in engaging visitors and in teaching concepts. Imperatives and methods to strengthen museum evaluation have been suggested and implemented in the past, but ultimately faced several challenges including the collection of visitor feedback in an efficient, non-intrusive way. The Ask Dr. Discovery project seeks to address the challenge of conducting efficient, affordable, and large-scale science museum evaluation via an interactive app aimed at collecting direct visitor feedback through use of the app and through questionnaires that also collect demographics. This thesis investigates how the demographics of metro Phoenix science museum visitors as a whole compare to the Hispanic/Latino population of visitors, and makes use of visitor feedback from Ask Dr. Discovery to provide useful data for science museum evaluation. An analysis of responses revealed that the majority of the participants in the study (n=785) were White (Non-Hispanic) (65.59%), were 36-45 years old (36.18%) and hold a graduate degree (27.64%). Most Hispanic/Latino participants in the study were 26-35 years old (36.36%) and completed some college (28.67%). Most participants from both participant groups have never visited the museum before (32.99% of all participants; 33.57% of all Hispanics/Latinos). Further analysis suggest that museum visits may be independent of age and visitor group size. Visitor interest in science museum exhibits may be independent of their use of free time science-related activities. Data suggests that there was no real difference in exhibit interest across two different versions of the app ("modes"). Analysis of negative visitor feedback showed different question types, questions asked, and time spent on the app. Data log questions revealed the difference in time spent on the app and complexity of questions asked between adults and children, as well as the location of participants in the museum. There was no major correlation between mode type and number of questions asked, and length of use and number of questions asked.
ContributorsFernandez, Ivan (Author) / Bowman, Judd (Thesis director) / Bowman, Catherine (Committee member) / Nelson, Brian (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Nebular emission-lines offer a powerful tool for studying the physical properties and chemical compositions of galaxies in the near and distant universe. They are excellent tracers of star formation activity in galaxies as well as efficient probes of intergalactic medium in the early universe. This dissertation presents findings from three different studies of emission-line galaxies (a.k.a. line emitters) at low and high redshifts, based on imaging and spectroscopic observations. The first study explores Hα emitters at z ~ 0.6 from the Cosmic Deep And Wide Narrow-band (DAWN) survey, providing robust measurements of the Hα luminosity function (LF) and the star-formation rate density (SFRD) at z ~ 0.6. The effects of different dust-extinction corrections on the measured LF were also investigated in this study. Owing to the observing strategy employed in this survey, this study demonstrates the importance of performing deep and wide-field observations, in order to robustly constrain the entire LF. In the second study, 21 Lyman-α emitter (LAE) candidates at z ~ 7 from the Lyman-Alpha Galaxies in the Epoch of Reionization (LAGER) survey were followed up spectroscopically, using Low Resolution Imaging Spectrometer (LRIS) on the Keck telescope. 15 of these were confirmed to be LAEs, obtaining a spectroscopic confirmation success rate of ~ 80% for LAGER LAE candidates. Apart from Lyman- α, no other rest-frame ultra-violet (UV) nebular lines were detected, with a 2σ upper limit for the ratio of NV/Lyα ≲ 0.27. These confirmations help validate the neutral Hydrogen fraction estimates from LAGER, which is consistent with a fully ionized universe at z ~ 7. The final study investigated the presence of black hole/active galactic nuclei (AGN) signatures among Green Pea (GP) galaxies, using mid-infrared (MIR) observations from the Wide-field Infrared Survey Explorer (WISE) mission. 31 GPs were selected as candidate AGN based on a stringent MIR color-color diagnostic including two GPs exhibiting notable variability in the shorter two WISE bandpasses. Given that GPs are one of the best analogs of high-redshift galaxies, findings from this study suggest that AGN activity could be responsible for the hard ionizing radiation observed in some GPs, which has crucial implications on the sources likely to have contributed towards cosmic reionization.
ContributorsHarish, Santosh Mudigundam (Author) / Rhoads, James E. (Thesis advisor) / Jacobs, Daniel C. (Thesis advisor) / Malhotra, Sangeeta (Committee member) / Bowman, Judd (Committee member) / Jansen, Rolf (Committee member) / Arizona State University (Publisher)
Created2022
Description
The balance between relative numbers, lifetime, and habitable zone (HZ) size of K stars (0.6 – 0.9 M⊙) in comparison with M (0.08 – 0.6 M⊙) and G (0.9 – 1.1 M⊙) stars makes them candidates to host “super-habitable” planets. Understanding the high- energy radiation environment of planets around these stars is crucial, since ultraviolet (UV) and X-ray radiation may cause severe photodissociation and ionization of the atmosphere, with the potential for complete erosion. In this thesis, I present the first broad study of the UV and X-ray evolution of K stars. I first focused on Galaxy Evolution Explorer (GALEX) and Ro ̈ntgen Satellit (ROSAT) photometric UV and X-ray evolutions of K stars and compared this with the age evolution of both early- (0.35 – 0.6 M⊙) and late-M (0.08 – 0.35 M⊙) stars. I found that the fractional UV and X-ray flux from M and K stars is similar; however, the wider and farther HZs of K stars mean that there is less incident UV radiation on HZ planets. Next, I led a spectroscopic study of 41 K stars using Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS) data to show that the UV line and continua emission show no decrease in flux beyond 650 Myr whereas early-M star flux declines by 150 Myr; therefore, the K star intrinsic UV flux is greater than early-M stars after this time. I suggest that this phenomenon is related to K star rotational spin-down stalling. Lastly, I revisited the GALEX and ROSAT data with newly-available distances from the Gaia mission for both K and M stars. I find that the UV flux for K stars is an order of magnitude higher for M stars at all ages and the flux in their respective HZs is similar. However, K star X-ray flux is an order of magnitude less in the HZ than for M stars. The age of decline shows a dependency on wavelength, a phenomenon which is not seen in either the early- or late-M star data. These results suggest thatK stars may not exhibit quite the advantage as HZ planet host stars as the scientific community originally thought.
ContributorsRichey-Yowell, Tyler (Author) / Shkolnik, Evgenya (Thesis advisor) / Patience, Jennifer (Committee member) / Jacobs, Daniel (Committee member) / Bowman, Judd (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2022