Management of a university satellite program with focus on a refrigerant-based propulsion system

The Missouri University of Science and Technology Satellite (M-SAT) design team has established a satellite program to develop a pair of satellites to perform an autonomous formation flight mission. The resulting configuration was assembled for the Air Force Research Lab University Nanosat Program. This document, written by the Program Manager and former member of the Propulsion subsystem, is a description of the management process used by the team to develop a satellite configuration. Included in the document is a discussion of team organization, techniques for managing a program, and lessons learned during the 2007 to 2008 timeframe. The managing techniques impact the development of subsystems. The propulsion system is discussed further as an example to highlight a successful subsystem in both management and design development. The propulsion system is required to perform orbital maneuvers and three-axis attitude control to complete the mission objective of autonomous formation flight. This thesis specifically documents the research and selection of hardware and the integration of the system into the primary satellite. Also, seal material selection and outgassing challenges are discussed --Abstract, page iii

Analysis of ion emitting jet structures during ionic liquid electrospraying

The ionic liquid [Bmim][DCA] is a propellant candidate for a standalone electrospray thruster or a dual-mode propulsion system. Characterization of positive polarity ions produced by [Bmim][DCA] capillary emitters with a nominal extraction voltage of 2.0 kV within a quadrupole and time-of-flight mass spectrometers is presented along with the predictions of propulsion performance. Flow rates from 0.05 to 2.18 nL/s are used to investigate the impact variations in the flow parameter have on the electrospray plume. The retarding potential analysis reveals ions emitted from the capillary are formed below the emitter potential of 500 eV. Angular distributions indicate broadening of both the beam current and mass distribution for increasing flow rates. Derived thrust and specific impulse change from 0.84 micro-Newtons and 200 s to 2.90 micro-Newtons and 80 s, respectively. Time-of-flight measurements delineate two distinct droplet distributions at approximately 2,000 to 40,000 amu/q and 50,000 to 300,000 amu/q. These multiply-charged droplet species, with wide mass-to-charge distributions, are due to the electric field conditions and associated charge range available within the parent jet. Additionally, the data show a transition to higher mass ions and droplets with increasing flow rate. The combination of two data sources allow for the assertion that ionic liquid electrospray from 0.05 to 2.18 nL/s does not conform to the traditional view of emission from the electrospray cone-jet. The mixed droplet and ion emission suggest that the primary jet disintegrates into secondary structures that are responsible for the emission species detected by the TOF instrument. --Abstract, page iv

Mitigating bias blind spot via a serious video game

We employed a serious video game to train participants on bias blind spot (BBS), capturing training effects on BBS mitigation and knowledge at three points in time. Experiment 1 (N = 703) compared the effects of hybrid training (a combination of implicit and explicit training) to implicit training; Experiment 2 (N = 620) tested the effects of just-in-time versus delayed feedback; and Experiment 3 (N = 626) examined the effects of singleplayer versus multiplayer learning environments. We also tested differences in game duration (30 vs. 60 minute play) and repetition (single vs. repeated play). Overall, the video game decreased BBS linearly over time and increased BBS knowledge at posttest, but knowledge decayed at 8-week posttest. These and other results are discussed, along with the implications, limitations, and future research directions

One-arcsecond line-of-sight pointing control on exoplanetsat, a three-unit CubeSat

ExoplanetSat is a proposed 10×10×34-cm space telescope designed to detect down to Earth-sized exoplanets in an orbit out to the habitable zone of bright, Sun-like stars via the transit method. Achieving this science objective requires one-arcsecond line-of-sight pointing control for the science CCD detector, an unprecedented requirement for CubeSats. A two-stage control architecture that coordinates coarse rigid-body attitude control with fine line-of-sight pointing control will be employed to meet this challenging pointing requirement. Detailed testing of the reaction wheels and CMOS detectors has been performed to extract key performance parameters used in simulations. The results of these simulations indicate that a 1.4 arcsecond pointing precision (3σ) is achievable. To meet the 1.0-arcsecond pointing requirement, several options are analyzed. In particular, a new technique to estimate reaction wheel vibrations for feed forward cancellation of reaction wheel vibrations is presented. This estimator adaptively estimates disturbances from noisy sensor measurements and effectively stores disturbance amplitude and phase in memory as a function of wheel speed. In addition to these simulation results, testing results from a hardware-in-the-loop (HWIL) testbed demonstrate the capability of the fine pointing control loop. Future plans for complete HWIL testing of the coarse and fine control loops are presented

Sperm Proteasomes Degrade Sperm Receptor on the Egg Zona Pellucida during Mammalian Fertilization

Despite decades of research, the mechanism by which the fertilizing spermatozoon penetrates the mammalian vitelline membrane, the zona pellucida (ZP) remains one of the unexplained fundamental events of human/mammalian development. Evidence has been accumulating in support of the 26S proteasome as a candidate for echinoderm, ascidian and mammalian egg coat lysin. Monitoring ZP protein degradation by sperm during fertilization is nearly impossible because those few spermatozoa that penetrate the ZP leave behind a virtually untraceable residue of degraded proteins. We have overcome this hurdle by designing an experimentally consistent in vitro system in which live boar spermatozoa are co-incubated with ZP-proteins (ZPP) solubilized from porcine oocytes. Using this assay, mimicking sperm-egg interactions, we demonstrate that the sperm-borne proteasomes can degrade the sperm receptor protein ZPC. Upon coincubation with motile spermatozoa, the solubilized ZPP, which appear to be ubiquitinated, adhered to sperm acrosomal caps and induced acrosomal exocytosis/formation of the acrosomal shroud. The degradation of the sperm receptor protein ZPC was assessed by Western blotting band-densitometry and proteomics. A nearly identical pattern of sperm receptor degradation, evident already within the first 5 min of coincubation, was observed when the spermatozoa were replaced with the isolated, enzymatically active, sperm-derived proteasomes. ZPC degradation was blocked by proteasomal inhibitors and accelerated by ubiquitin-aldehyde(UBAL), a modified ubiquitin protein that stimulates proteasomal proteolysis. Such a degradation pattern of ZPC is consistent with in vitro fertilization studies, in which proteasomal inhibitors completely blocked fertilization, and UBAL increased fertilization and polyspermy rates. Preincubation of intact zona-enclosed ova with isolated active sperm proteasomes caused digestion, abrasions and loosening of the exposed zonae, and significantly reduced the fertilization/polyspermy rates after IVF, accompanied by en-mass detachment of zona bound sperm. Thus, the sperm borne 26S proteasome is a candidate zona lysin in mammals. This new paradigm has implications for contraception and assisted reproductive technologies in humans, as well as animals

Continental scale patterns and predictors of fern richness and phylogenetic diversity

Because ferns have a wide range of habitat preferences and are widely distributed, they are an ideal group for understanding how diversity is distributed. Here we examine fern diversity on a broad-scale using standard and corrected richness measures as well as phylogenetic indices; in addition we determine the environmental predictors of each diversity metric. Using the combined records of Australian herbaria, a dataset of over 60,000 records was obtained for 89 genera to infer richness. A molecular phylogeny of all the genera was constructed and combined with the herbarium records to obtain phylogenetic diversity patterns. A hotspot of both taxic and phylogenetic diversity occurs in the Wet Tropics of northeastern Australia. Although considerable diversity is distributed along the eastern coast, some important regions of diversity are identified only after sample-standardization of richness and through the phylogenetic metric. Of all of the metrics, annual precipitation was identified as the most explanatory variable, in part, in agreement with global and regional fern studies. However, precipitation was combined with a different variable for each different metric. For corrected richness, precipitation was combined with temperature seasonality, while correlation of phylogenetic diversity to precipitation plus radiation indicated support for the species-energy hypothesis. Significantly high and significantly low phylogenetic diversity were found in geographically separate areas. These separate areas correlated with different climatic conditions such as seasonality in precipitation. The phylogenetic metrics identified additional areas of significant diversity, some of which have not been revealed using traditional taxonomic analyses, suggesting that different ecological and evolutionary processes have operated over the continent. Our study demonstrates that it is possible and vital to incorporate evolutionary metrics when inferring biodiversity hotspots from large compilations of data

Mitigation of Cognitive Bias with a Serious Game: Two Experiments Testing Feedback Timing and Source

One of the benefits of using digital games for education is that games can provide feedback for learners to assess their situation and correct their mistakes. We conducted two studies to examine the effectiveness of different feedback design (timing, duration, repeats, and feedback source) in a serious game designed to teach learners about cognitive biases. We also compared the digital game-based learning condition to a professional training video. Overall, the digital game was significantly more effective than the video condition. Longer durations and repeats improve the effects on bias-mitigation. Surprisingly, there was no significant difference between just-in-time feedback and delayed feedback, and computer-generated feedback was more effective than feedback from other players

Planetary Candidates Observed by Kepler VI: Planet Sample from Q1-Q16 (47 Months)

\We present the sixth catalog of Kepler candidate planets based on nearly 4 years of high precision photometry. This catalog builds on the legacy of previous catalogs released by the Kepler project and includes 1493 new Kepler Objects of Interest (KOIs) of which 554 are planet candidates, and 131 of these candidates have best fit radii <1.5 R_earth. This brings the total number of KOIs and planet candidates to 7305 and 4173 respectively. We suspect that many of these new candidates at the low signal-to-noise limit may be false alarms created by instrumental noise, and discuss our efforts to identify such objects. We re-evaluate all previously published KOIs with orbital periods of >50 days to provide a consistently vetted sample that can be used to improve planet occurrence rate calculations. We discuss the performance of our planet detection algorithms, and the consistency of our vetting products. The full catalog is publicly available at the NASA Exoplanet Archive.Comment: 18 pages, to be published in the Astrophysical Journal Supplement Serie

Assessing biodiversity and endemism using phylogenetic methods across multiple taxonomic groups

Identifying geographical areas with the greatest representation of the tree of life is an important goal for the management and conservation of biodiversity. While there are methods available for using a single phylogenetic tree to assess spatial patterns of biodiversity, there has been limited exploration of how separate phylogenies from multiple taxonomic groups can be used jointly to map diversity and endemism. Here, we demonstrate how to apply different phylogenetic approaches to assess biodiversity across multiple taxonomic groups. We map spatial patterns of phylogenetic diversity/endemism to identify concordant areas with the greatest representation of biodiversity across multiple taxa and demonstrate the approach by applying it to the Murray–Darling basin region of southeastern Australia. The areas with significant centers of phylogenetic diversity and endemism were distributed differently for the five taxonomic groups studied (plant genera, fish, tree frogs, acacias, and eucalypts); no strong shared patterns across all five groups emerged. However, congruence was apparent between some groups in some parts of the basin. The northern region of the basin emerges from the analysis as a priority area for future conservation initiatives focused on eucalypts and tree frogs. The southern region is particularly important for conservation of the evolutionary heritage of plants and fishes