Determination of Curve Number for snowmelt-runoff floods in a small catchment

One of the widely used methods for predicting flood runoff depth from ungauged catchments is the curve number (CN) method, developed by Soil Conservation Service (SCS) of US Department of Agriculture. The CN parameter can be computed directly from recorded rainfall depths and\ud direct runoff volumes in case of existing data. In presented investigations, the CN parameter has been computed for snowmelt-runoff events based on snowmelt and rainfall measurements. All required data has been gathered for a small agricultural catchment (A = 23.4 km2) of Zagożdżonka river, located in Central Poland. The CN number received from 28 snowmelt-runoff events has been compared with CN computed from rainfall-runoff events for the same catchment. The CN parameter, estimated empirically varies from 64.0 to 94.8. The relation between CN and snowmelt depth was investigated in a similar procedure to relation between CN and rainfall depth

A Tuned Single Parameter for Representing Conjunction Risk

Satellite conjunction assessment risk analysis is a subjective enterprise that can benefit from quantitative aids and, to this end, NASA/GSFC has developed a fuzzy logic construct - called the F-value - to attempt to provide a statement of conjunction risk that amalgamates multiple indices and yields a more stable intra-event assessment. This construct has now sustained an extended tuning procedure against heuristic analyst assessment of event risk. The tuning effort has resulted in modifications to the calculation procedure and the adjustment of tuning coefficients, producing a construct with both more predictive force and a better statement of its error

Consideration of Collision "Consequence" in Satellite Conjunction Assessment and Risk Analysis

Classic risk management theory requires the assessment of both likelihood and consequence of deleterious events. Satellite conjunction risk assessment has produced a highly-developed theory for assessing collision likelihood but holds a completely static solution for collision consequence, treating all potential collisions as essentially equally worrisome. This may be true for the survival of the protected asset, but the amount of debris produced by the potential collision, and therefore the degree to which the orbital corridor may be compromised, can vary greatly among satellite conjunctions. This study leverages present work on satellite collision modeling to develop a method by which it can be estimated, to a particular confidence level, whether a particular collision is likely to produce a relatively large or relatively small amount of resultant debris and how this datum might alter conjunction remediation decisions. The more general question of orbital corridor protection is also addressed, and a preliminary framework presented by which both collision likelihood and consequence can be jointly considered in the risk assessment process

Predicting Space Weather Effects on Close Approach Events

The NASA Robotic Conjunction Assessment Risk Analysis (CARA) team sends ephemeris data to the Joint Space Operations Center (JSpOC) for conjunction assessment screening against the JSpOC high accuracy catalog and then assesses risk posed to protected assets from predicted close approaches. Since most spacecraft supported by the CARA team are located in LEO orbits, atmospheric drag is the primary source of state estimate uncertainty. Drag magnitude and uncertainty is directly governed by atmospheric density and thus space weather. At present the actual effect of space weather on atmospheric density cannot be accurately predicted because most atmospheric density models are empirical in nature, which do not perform well in prediction. The Jacchia-Bowman-HASDM 2009 (JBH09) atmospheric density model used at the JSpOC employs a solar storm active compensation feature that predicts storm sizes and arrival times and thus the resulting neutral density alterations. With this feature, estimation errors can occur in either direction (i.e., over- or under-estimation of density and thus drag). Although the exact effect of a solar storm on atmospheric drag cannot be determined, one can explore the effects of JBH09 model error on conjuncting objects' trajectories to determine if a conjunction is likely to become riskier, less risky, or pass unaffected. The CARA team has constructed a Space Weather Trade-Space tool that systematically alters the drag situation for the conjuncting objects and recalculates the probability of collision for each case to determine the range of possible effects on the collision risk. In addition to a review of the theory and the particulars of the tool, the different types of observed output will be explained, along with statistics of their frequency

Evaluating Probability of Collision (Pc) Uncertainty

No abstract availabl

Optimization of broadband semiconductor chirped mirrors with genetic algorithm

Genetic algorithm was applied for optimization of dispersion properties in semiconductor Bragg reflectors for applications in femtosecond lasers. Broadband, large negative group-delay dispersion was achieved in the optimized design: The group-delay dispersion (GDD) as large as −3500 fs2 was theoretically obtained over a 10-nm bandwidth. The designed structure was manufactured and tested, providing GDD −3320 fs2 over a 7-nm bandwidth. The mirror performance was verified in semiconductor structures grown with molecular beam epitaxy. The mirror was tested in a passively mode-locked Yb:KYW laser

Finite CA, Total Pc, and a Substantially-Larger Catalog

No abstract availabl

Launch COLA Operations: An Examination of Data Products, Procedures, and Thresholds

NASA GSFC and KSC, acting in response to headquarters NASA direction, performed a year-long study of launch collision avoidance (LCOLA) operations in order to determine and recommend best risk assessment and mitigation practices. The following condenses the findings and recommendations of the study into one short summary, a more expanded version of which appears as Section 10

Warunki termiczne i śnieżne zim oraz wezbrania zimowe na przykładzie zlewni rzeki Zagożdżonki

Thermal and snowy conditions in Zagożdżonka River catchment during hydrological years 2003–2013 and winter floods are presented in paper. The meteorological and hydrological data, such as maximum, minimum, mean diurnal air temperatures, daily snow cover depth, and water discharge, collected at Czarna station (WULS-SGGW) have been used. Meteorological conditions were analyzed using indexes proposed by Paczos. Temperate cold and extraordinarily low snowy winters has dominated in Zagożdżonka catchment in presented period of time. Winter floods as a result of snowmelt have been observed almost each year, except 2008 when winter was mild and extremely low snowy. The relation between winter severity index (WOz) and winter snowiness index (WSn) has been estimated, as well as the relation between winter snowiness index and maximum discharge (Qmax).Wykorzystując wskaźniki ostrości termicznej i śnieżności zim według Paczosa, przedstawiono warunki termiczne i śnieżne zim na obszarze nizinnej zlewni rzeki Zagożdżonki oraz scharakteryzowano wezbrania zimowe, odnotowane w badanym okresie. Podstawowe dane meteorologiczne i hydrologiczne, takie jak temperatura powietrza (maksymalna, minimalna i średnia), grubość pokrywy śnieżnej, wysokość opadów, stany wody oraz zmącenie wody w okresach zimowych lat hydrologicznych 2002–2013, pochodziły ze stacji pomiarowej SGGW zlokalizowanej w miejscowości Czarna, na obszarze badanej zlewni. W badanym okresie na obszarze zlewni Zagożdżonki dominowały zimy umiarkowanie chłodne i niezwykle małośnieżne. Niemal w każdym roku obserwowano wezbrania, których bezpośrednią przyczyną było topnienie śniegu. Wyjątek stanowił rok hydrologiczny 2008, kiedy zima była łagodna i ekstremalnie małośnieżna. Istnieje korelacja pomiędzy wskaźnikiem ostrości zimy a wskaźnikiem śnieżności. Istnieje również zależność pomiędzy wskaźnikiem śnieżności a przepływem maksymalnym w okresie zimowym