An Analysis of Radio-Frequency Geolocation Techniques for Satellite Systems Design

This research 1) evaluates the effectiveness of CubeSat radio-frequency geolocation and 2) analyzes the sensitivity of different RF algorithms to system parameters. A MATLAB simulation is developed to assess geolocation accuracy for variable system designs and techniques (AOA, TDOA, T/FDOA). An unconstrained maximum likelihood estimator (MLE) and three different digital elevation models (DEM) are utilized as the surface of the Earth constraint to improve geolocation accuracy. The results presented show the effectiveness of the MLE and DEM techniques, the sensitivity of AOA, TDOA, and T/FDOA algorithms, and the system level performance of a CubeSat geolocation cluster in a 500km circular orbit

Atmospheric mesoscale modeling of water and clouds during northern summer on Mars

AbstractFor a key season in the annual water cycle (Ls∼120°) a mesoscale model is used to study atmospheric water vapor and water ice clouds in the northern polar region of Mars. Model results at high-resolution (15km) allow the examination of various mesoscale aspects of the circulation in this complex (topography, albedo and thermal inertia) region. A simple cloud scheme is used, where only the mean cloud particle size is carried, and nucleation is not explicitly treated. For this study, new high-resolution maps of albedo and thermal inertia were developed (poleward of 60°N), and model ground temperatures are in good agreement with observations at high resolution, typically within ∼5K of TES (for ice and non-ice locations at AM and PM times of day). Diurnal mean sublimation rates are greatest along the edges of the polar dome and the largest outliers (∼25–50μm/sol). This is a consequence of widespread stability (atmospheric inversion) over the cold interiors of the largest ice surfaces, as well as strong ventilating winds that are modeled around the polar dome with sufficient spatial resolution. The structure of high latitude atmospheric water vapor is complex, especially so near Phoenix. Dynamically, two factors are responsible: (1) the transient circulations that form in the baroclinic zone around the polar dome and (2) a “storm zone” that forms on the poleward slopes of Alba Patera where there is additional transient activity that has a sizeable effect on the Phoenix region. This “storm zone” forms because of a rapidly evolving aspect of the regional circulation, and it plays a key role in the seasonally recurring annular cloud (that is simulated in this study). Also simulated are observations made during the Phoenix mission that seem to be dynamically related to the appearance of the annular cloud. Together this may signify a seasonal transition in the region. To simulate realistic clouds over the polar region (compared with opacity observations and imagery), a sufficiently realistic circulation appears to be important, and relatively high spatial resolution is needed for this. If a low-resolution run (135km, no nests) is compared to a high-resolution run (two levels of nesting to 15km in the polar region), we find that the high-resolution case produces ten times less cloud ice over the most polar latitudes. The activation of the first nest (45km) produces a sufficiently realistic circulation, such that excess vapor and cloud ice are readily ventilated equatorward from polar latitudes. A more sophisticated cloud scheme might serve to reduce the sensitivity seen in this study. However, sufficient spatial resolution is what causes the circulation to become realistic, and in this regard microphysics is not involved

SeaWiFS calibration and validation plan, volume 3

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) will be the first ocean-color satellite since the Nimbus-7 Coastal Zone Color Scanner (CZCS), which ceased operation in 1986. Unlike the CZCS, which was designed as a proof-of-concept experiment, SeaWiFS will provide routine global coverage every 2 days and is designed to provide estimates of photosynthetic concentrations of sufficient accuracy for use in quantitative studies of the ocean's primary productivity and biogeochemistry. A review of the CZCS mission is included that describes that data set's limitations and provides justification for a comprehensive SeaWiFS calibration and validation program. To accomplish the SeaWiFS scientific objectives, the sensor's calibration must be constantly monitored, and robust atmospheric corrections and bio-optical algorithms must be developed. The plan incorporates a multi-faceted approach to sensor calibration using a combination of vicarious (based on in situ observations) and onboard calibration techniques. Because of budget constraints and the limited availability of ship resources, the development of the operational algorithms (atmospheric and bio-optical) will rely heavily on collaborations with the Earth Observing System (EOS), the Moderate Resolution Imaging Spectrometer (MODIS) oceans team, and projects sponsored by other agencies, e.g., the U.S. Navy and the National Science Foundation (NSF). Other elements of the plan include the routine quality control of input ancillary data (e.g., surface wind, surface pressure, ozone concentration, etc.) used in the processing and verification of the level-0 (raw) data to level-1 (calibrated radiances), level-2 (derived products), and level-3 (gridded and averaged derived data) products

Shear thickening of cornstarch suspensions as a re-entrant jamming transition

We study the rheology of cornstarch suspensions, a dense system of non-Brownian particles that exhibits shear thickening, i.e. a viscosity that increases with increasing shear rate. Using MRI velocimetry we show that the suspension has a yield stress. From classical rheology it follows that as a function of the applied stress the suspension is first solid (yield stress), then liquid and then solid again when it shear thickens. The onset shear rate for thickening is found to depend on the measurement geometry: the smaller the gap of the shear cell, the lower the shear rate at which thickening occurs. Shear thickening can then be interpreted as the consequence of the Reynolds dilatancy: the system under flow wants to dilate but instead undergoes a jamming transition because it is confined, as confirmed by measurement of the dilation of the suspension as a function of the shear rate

Surface Plasmon Polariton microscope with Parabolic Reflectors

We report the realization of a two--dimensional optical microscope for surface plasmons polaritons (SPPs) based on parabolic Bragg mirrors. These mirrors are built from lithographically fabricated gold nanostructures on gold thin films. We show by direct imaging by leakage radiation microscopy that the magnification power of the SPP microscope follows basic predictions of geometrical optics. Spatial resolution down to the value set by the diffraction limit is demonstrated.Comment: Opt.Lett.32, 2414 (2007

Characterization of the Cancer Spectrum in Men With Germline BRCA1 and BRCA2 Pathogenic Variants Results From the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA)

Importance The limited data on cancer phenotypes in men with germline BRCA1 and BRCA2 pathogenic variants (PVs) have hampered the development of evidence-based recommendations for early cancer detection and risk reduction in this population. Objective To compare the cancer spectrum and frequencies between male BRCA1 and BRCA2 PV carriers. Design, Setting, and Participants Retrospective cohort study of 6902 men, including 3651 BRCA1 and 3251 BRCA2 PV carriers, older than 18 years recruited from cancer genetics clinics from 1966 to 2017 by 53 study groups in 33 countries worldwide collaborating through the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA). Clinical data and pathologic characteristics were collected. Main Outcomes and Measures BRCA1/2 status was the outcome in a logistic regression, and cancer diagnoses were the independent predictors. All odds ratios (ORs) were adjusted for age, country of origin, and calendar year of the first interview. Results Among the 6902 men in the study (median [range] age, 51.6 [18-100] years), 1634 cancers were diagnosed in 1376 men (19.9%), the majority (922 of 1,376 [67%]) being BRCA2 PV carriers. Being affected by any cancer was associated with a higher probability of being a BRCA2, rather than a BRCA1, PV carrier (OR, 3.23; 95% CI, 2.81-3.70; P <.001), as well as developing 2 (OR, 7.97; 95% CI, 5.47-11.60; P <.001) and 3 (OR, 19.60; 95% CI, 4.64-82.89; P <.001) primary tumors. A higher frequency of breast (OR, 5.47; 95% CI, 4.06-7.37; P <.001) and prostate (OR, 1.39; 95% CI, 1.09-1.78; P = .008) cancers was associated with a higher probability of being a BRCA2 PV carrier. Among cancers other than breast and prostate, pancreatic cancer was associated with a higher probability (OR, 3.00; 95% CI, 1.55-5.81; P = .001) and colorectal cancer with a lower probability (OR, 0.47; 95% CI, 0.29-0.78; P = .003) of being a BRCA2 PV carrier. Conclusions and Relevance Significant differences in the cancer spectrum were observed in male BRCA2, compared with BRCA1, PV carriers. These data may inform future recommendations for surveillance of BRCA1/2-associated cancers and guide future prospective studies for estimating cancer risks in men with BRCA1/2 PVs. This cohort study compares the cancer spectrum and frequencies between male BRCA1 and BRCA2 pathogenic variant carriers. Question Are there cancer phenotype differences between male BRCA1 and BRCA2 pathogenic variant carriers? Findings In this cohort study of 6902 men with a BRCA1 or BRCA2 pathogenic variant, being affected by cancer, particularly breast, prostate, and pancreatic cancers and developing multiple primary tumors, was associated with a higher probability for a man of being a BRCA2, rather than a BRCA1, pathogenic variant carrier. Meaning Surveillance programs in men with BRCA1 and BRCA2 pathogenic variants should be tailored in light of these gene-specific cancer phenotype differences. These results may inform the design of prospective studies on cancer risks in male BRCA1 and BRCA2 pathogenic variant carriers.Peer reviewe

A mesoscale model study of summertime atmospheric circulations in the north polar region of Mars

The Oregon State University Mars MM5 was used in a comprehensive high-resolution study of northern polar summertime circulations. Three simulations (Ls = 120, Ls = 135, and Ls = 150) characterize the changing circulation. The atmosphere is dry, and model dynamics are hydrostatic. A modified TES thermal inertia map provides a realistic simulation of the polar thermal environment. The highest-resolution nest (18 km) resolves complex flows near the cap; zonal-mean easterlies (~10 m/s) and zonal-mean katabatic winds (~5 m/s) near the surface are relatively steady during this study. Katabatic flows are shallow (~300 m); the easterlies are deeper (~1.5 km). Transient eddies are very important within the first scale height; they are excited by mechanisms, and at locations, that change dramatically during this short study period. At Ls = 120 they form along the residual cap edge with a zonal wave number one structure, producing strong excursion winds (10–15 m/s) that blow consistently across the cap. By Ls = 135, strong eddies are seen to form on the northern slopes of Alba Patera and Tharsis. These eddies are quite suggestive of the large annular cloud structures seen in Hubble Space Telescope and Mars Orbital Camera imagery at this location and season and can traverse the high latitudes to reach the residual cap before dissipating. Eddies in the earlier two simulations appear to be primarily excited by energetic flows near the surface. By Ls = 150 an early fall polar jet causes strong winter-like baroclinic eddies to develop. The transient eddies found in this study are probably important in the water cycle of the northern residual cap