Signal Characteristics of Civil GPS Jammers

This paper surveys the signal properties of 18 commercially available GPS jammers based on experimental data. The paper is divided into two distinct tests. The first characterizes the jamming signals, and the second test determines the effective range of 4 of the jammers. The first test uses power spectra from discrete Fourier transforms (DFTs) of the time series data to show that all the jammers employ approximately the same jamming method, i.e. linear frequency modulation of a single tone. The spectra also show that there are significant jammer-to-jammer variations, including between jammers of the same model, and that a given jammer’s signal may vary over time. The first test also includes measurements of signal power within frequency bands centered at the L1 and L2 frequencies, along with the sweep periods and the sweep range at both frequencies. The second test presents measurements of the attenuation of the jamming signal necessary to allow a commercially available GPS receiver to acquire and track signals from a GPS simulator. From the attenuation levels and some assumptions about the antennas used, upper limits on the effective jamming ranges are calculated for 4 of the jammers, with a resulting maximum range of 6–9 km.Aerospace Engineering and Engineering Mechanic

Space-Based Capstone: Public-Private-Academic Partnership in the Making

The Electronic Systems Engineering Technology (ESET) Program at Texas A&M University provides a recognized undergraduate program with an emphasis in electronics, communication, embedded systems, testing, instrumentation and control systems. The program combines engineering and industrial knowledge and methods to develop, design, and implement new innovative products through a two-semester long Senior Capstone Project. Capstone is designed to prepare future engineers by bridging the gap between the classroom and industry. Students are required to form teams of two to six members which allows them to develop the skills necessary to succeed in a diverse industry setting. Each team is required to use their knowledge and skills to design, develop, document, and deliver a real-world project equivalent to the assignments they will soon receive as professional engineers. Following NASA’s approval for funding the development of a research facility named Hermes, a Capstone team, named Microgravity Automated Research Systems (MARS), was sponsored by T STAR, a local space commercialization company, to develop the electronics portion of the facility. Hermes will reside on the International Space Station for five years in the hopes of streamlining the development of experiments that require extended periods of time in microgravity environments. The Hermes facility will host and manage up to four experiments at a time while allowing for the downlink of experiment data to an Earth station, and the uplink of commands to change experiment parameters. Experiments will adhere to a power budget and communication standard established by MARS so that experiments can be swapped out during the facility’s lifetime. MARS will work with the Mobile Integrated Solutions Laboratory (MISL), an undergraduate applied research lab, in order to prepare them to maintain support for Hermes in the future.Cockrell School of Engineerin

Swarm Flyby Gravimetry

This study describes a new technology for discerning the gravity fields and mass distribution of a solar system small body, without requiring dedicated orbiters or landers. Instead of a lander, a spacecraft releases a collection of small, simple probes during a flyby past an asteroid or comet. By tracking those probes from the host spacecraft, one can estimate the asteroid's gravity field and infer its underlying composition and structure. This approach offers a diverse measurement set,equivalent to planning and executing many independent and unique flyby encounters of a single spacecraft. This report assesses a feasible hardware implementation, derives the underlying models,and analyzes the performance of this concept via simulation.In terms of hardware, a small, low mass, low cost implementation is presented, which consists of a dispenser and probes. The dispenser contains roughly 12 probes in a tube and has a total size commensurate with a 6U P-Pod. The probes are housed in disc shaped sabots. When commanded,the dispenser ejects the top-most probe using a linear motor. The ejected probe separates from its sabots and unfolds using internal springs. There are two types of probes, each designed for a particular tracking modality. The reflective probe type, tracked by a telescope, unfolds to forma diffusely reflective sphere. The retroreflector probe type, tracked by a lidar, unfolds to form a corner-cube retroreflector assembly. Both types are designed to spherical so that their attitude doesn't affect the spacecraft's tracking performance.This analysis indicates that the point-mass term of small bodies larger than roughly 500 m in diameter can be observed from a host spacecraft that tracks locally deployed probes throughout a flyby to an uncertainty of better than 5%. The conditions by which this measurement is possible depends on the characteristics of the asteroid (size, type), the flyby velocity, and the type of tracking available (angles-only or angles+ranging). For most encounters, a few (1-3) well placed probes can be very effective, with marginal improvement for additional probes. Given realistic deployment errors, an encounter may require roughly 10-12 probes to ensure that 1-3 achieve their target. Long duration tracking of probes flying by large asteroids (>5 km diameter) can sometimes provide observability of the gravity field's first spherical harmonic, J( sub 2). In summary, this method offers a feasible, affordable approach to enabling or augmenting flyby science

Avian Extraembryonic Membranes Respond to Yolk Corticosterone Early in Development

During times of maternal stress, developing embryos can be exposed to elevated levels of glucocorticoids which can affect development and permanently alter offspring phenotype. In placental species, the placenta mediates fetal exposure to maternal glucocorticoids via metabolism, yet the placenta itself responds to glucocorticoids to regulate offspring growth and development. In oviparous species, maternal glucocorticoids can be deposited into the egg yolk and are metabolized early in development. This metabolism is mediated by the extraembryonic membranes, but it is unknown if the extraembryonic membranes also respond to maternal glucocorticoids in a way comparable to the placenta. In this study, we quantified the expression of acyl-CoA thioesterase 13 (Acot13) as an initial marker of the membrane\u27s response to corticosterone in chicken (Gallus gallus) eggs. Acot13 regulates fatty acid processing in the embryo, to potentially regulate resource availability during development. We addressed the following questions using Acot13 expression: 1) Do the extraembryonic membranes respond to yolk corticosterone early in development? 2) Is the response to corticosterone dependent on the dose of corticosterone? 3) What is the duration of the response to corticosterone? 4) Does a metabolite of corticosterone (5β-corticosterone) elicit the same response as corticosterone? We found that corticosterone significantly induces the expression of Acot13 on day four of development and that expression of Acot13 increases with the dose of corticosterone. Further, we found expression of Acot13 is significantly elevated by corticosterone on days four and six of development compared to oil treated eggs, but not on days eight and ten. Although this response is transient, it occurs during a critical period of development and could initiate a cascade of events that ultimately alter offspring phenotype. Finally, we found that 5β-corticosterone does not increase the expression of Acot13, indicating that metabolism inactivates corticosterone. Ultimately, this study provides insight into the mechanisms underlying how maternally deposited glucocorticoids can affect embryonic development

The dissolution behaviour of titanium oxide phases in synthetic Bayer liquors at 90 C

Many of the bauxites currently being processed to alumina contain titanium minerals, yet little fundamental knowledge is available regarding their dissolution behaviour in Bayer liquors. In this paper the dissolution of various titanium oxide phases (anatase, rutile, sodium titanate and calcium titanate) are presented. It is shown that rutile, calcium titanate and sodium titanate have the expected dissolution behaviour, which increases with free caustic concentration. Anatase, too, generally increases in dissolution with free caustic concentration. However, anatase is shown to have an anomalous behaviour when gibbsite co-precipitates. In this case, the dissolution of anatase does not follow the expected free caustic trend. According to the data presented, the most probable cause is an impervious aluminium/sodium titanate surface layer hindering further dissolution

Economic Impact of the Cleantech Sector in the Austin-Round Rock-San Marcos MSA

Economic impact report for the clean technology sector in central Texas, commissioned by CleanTX and supported by the Austin Technology Incubator and Civic Analytics. The study finds that the cleantech sector in the Austin region directly employs nearly 20,000 individuals and contributes approximately $2.5 billion to the region's GDP. In addition, it projects cleantech employment from 2014-2020 to grow 11.24% in the Austin MSA, as compared with 9.3% growth in the sector over the same period at the state level, and 6.37% nationally. The report identifies seven specific technology areas which represent opportunities for growth: renewables; energy storage and "smart grid" technologies; smart cities and resilient infrastructure; autonomous vehicles and connected mobility; water management; recycling and waste management; and advanced manufacturing.IC2 Institut