Where the river meets the sea : an initial investigation into the Riverine tidal freshwater zone

Riverine tidal freshwater zones (RTFZs) are transitional environments between terrestrial and coastal waters that have freshwater chemistry and tidal physics, and are neither river nor estuary. The residence time dynamics of RTFZs have not yet been discussed in the literature, but may ultimately control the timing and magnitude of freshwater and nutrient coastal discharges. Furthermore, climate change threatens to alter the nexus between the terrestrial hydrologic cycle and the coastal tidal environment where the RTFZ resides. This dissertation provides the foundation for investigations into RTFZs and their subsequent residence times. An initial residence time analysis of 15 tidal river reaches along the south Texas Gulf Coast introduces tidal river reaches into the lentic/lotic nomenclature. This residence time analysis also quantifies the vernacular of lentic (reservoir-like) and lotic (riverine) systems via the Freshwater Continuum Classification (FCC). The FCC framework also incorporates temporal hydrologic variability, which is typically absent from other lentic/lotic classifications. Further analysis on one of these systems (Aransas River, TX, USA) revealed an RTFZ. The analysis empirically observed RTFZ responses to precipitation and tide, while providing the RTFZ definition. The RTFZ is defined by three longitudinal points of interest: λ₁ – upstream limit of brackish water, downstream limit of freshwater, and downstream boundary of RTFZ; λ₂ – upstream limit of bidirectional tidal velocities; λ₃ – upstream limit of tidal stage fluctuations and of the RTFZ. The RTFZ was typically (median) 59.9 km long and typically (median) began 11.84 km upstream (15.43 km/11.16 km, max/min) of the river mouth. From field data collected during RTFZ isolation, a tidal rating curve was created to model tidal discharge. The tidal rating curve expanded on traditional non-tidal gauging methods by incorporating stage-rate-of-change observations into the typical stage to discharge relationship. The method was performed on several sites along the Mission and Aransas Rivers, TX, USA, and twelve USGS tidal gauging stations, and resulted in strong agreement between estimated and observed discharge (i.e., r² > 0.70). With the tidal discharge estimations and RTFZ observations, future investigations should focus on RTFZ residence times and their impacts on estuarine ecology.Geological Science

Viking '75 spacecraft design and test summary. Volume 3: Engineering test summary

The engineering test program for the lander and the orbiter are presented. The engineering program was developed to achieve confidence that the design was adequate to survive the expected mission environments and to accomplish the mission objective

Only distance matters - non-choosy females in a poison frog population

Background: Females have often been shown to exhibit preferences for certain male traits. However, little is known about behavioural rules females use when searching for mates in their natural habitat. We investigated mate sampling tactics and related costs in the territorial strawberry poison frog (Oophaga pumilio) possessing a lek-like mating system, where both sequential and simultaneous sampling might occur. We continuously monitored the sampling pattern and behaviour of females during the complete period between two successive matings. Results: We found no evidence that females compared males by visiting them. Instead females mated with the closest calling male irrespective of his acoustic and physical traits, and territory size. Playback experiments in the natural home ranges of receptive females revealed that tested females preferred the nearest speaker and did not discriminate between low and high call rates or dominant frequencies. Conclusions: Our results suggest that females of O. pumilio prefer the closest calling male in the studied population. We hypothesize that the sampling tactic in this population is affected by 1) a strongly female biased sex ratio and 2) a low variance in traits of available males due to strong male-male competition, preventing low quality males from defending a territory and mating

Mars Orbiter Study. Volume 2: Mission Design, Science Instrument Accommodation, Spacecraft Design

Spacecraft system and subsystem designs were developed at the conceptual level to perform either of two Mars Orbiter Missions, a Climatology Mission and an Aeronomy Mission. The objectives of these missions are to obtain and return data to increase knowledge of Mars

The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm−1. TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described

Analysis of spacecraft anomalies

The anomalies from 316 spacecraft covering the entire U.S. space program were analyzed to determine if there were any experimental or technological programs which could be implemented to remove the anomalies from future space activity. Thirty specific categories of anomalies were found to cover nearly 85 percent of all observed anomalies. Thirteen experiments were defined to deal with 17 of these categories; nine additional experiments were identified to deal with other classes of observed and anticipated anomalies. Preliminary analyses indicate that all 22 experimental programs are both technically feasible and economically viable

Proceedings of the Sixth Annual Precise Time and Time Interval (PTTI) Planning Meeting

Time and frequency measurements are described for navigation and reference systems. Time measuring instruments and experiments performed are discussed

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression