Structure of an Ensemble of Insectivorous Bats

Ensembles of species show distinct characteristics that may permit resource partitioning but few studies focus on more than one or two traits. Using seven sympatric Jamaican bats, I examined features which could allow for spatial, temporal, behavioural and dietary partitioning including wing morphology, echolocation characteristics, flight behaviour, habitat use, and diet. Using acoustic arrays I compared activity patterns at different sites to determine temporal and spatial partitioning and generated flight paths to determine flight speeds. From captured bats I measured wing morphology to examine morphological differences and did genetic analysis of guano to determine dietary partitioning. Morphology, call structure and flight speeds suggested division into cluttered, edge and open foraging habitats. Species sharing habitats partitioned them in time. I found little dietary overlap among species or between seasons. In summary, the ensemble exhibited partitioning in all five dimensions I examined, suggesting multi-dimensional features may aid in ensemble resource division

Paper Session I-B - Nuclear Thermal Rocket Propulsion Application to Mars Missions

This paper discusses vehicle configuration options using nuclear thermal rocket (NTR) propulsion application to Mars missions. A reference mission in 2016 using an opposition-class Mars transfer trajectory is assumed. The total mission duration is 435 days. A single 75,000-lb-thrust nuclear engine is used for all major propulsive maneuvers. The studies indicate that three perigee kick burns upon leaving Earth result in the lowest stage weights required in low Earth orbit (LEO). The stay time on Mars is assumed to be 30 days. On the interplanetary return leg en route to Earth, a gravity assist by Venus is employed. The reference mission assumes that the nuclear engine delivers a specific impulse of 925 s with an engine thrust-to-weight ratio of 4. The total stage thrust-to-weight ratio was 0.06. To determine which engine parameters were most critical to good mission performance, calculations were performed over arange of specific impulses and thrust-to-weight ratios. One of the major conclusions resulting from this study is that engine specific impulse is the single most important engine parameter in reducing overall stage weight, provided the engine thrust-to-weight ratio is above approximately 4. Lower engine thrust-to-weight ratios were found to incur severe performance penalties

Paper Session III-B - Mars Transportation System Synthesis

President George Bush\u27s 1989 challenge to America to support the Space Exploration Initiative (SEI) of Back to the Moon and Manned Mission to Mars gives the space industry an opportunity to achieve effective and efficient space transportation systems (STS\u27s). This paper presents performance and requirements synthesized to support the manned Mars mission of the SEI. The information presented focuses primarily on the Mars transportation system (MTS), which uses nuclear thermal rocket (NTR) propulsion technology associated with accomplishing the manned Mars mission. Data are also shown for a propulsion system options comparison of chemical/ aerobrake and nuclear electric propulsion (NEP) systems

Optical Designs for a Multi-Beam 340 and 625/640 GHz Spaceborne Climate Research Instrument

We report on an ongoing study where different optical configurations for a multi-beam limb-viewing (four to eight receiver channels at 340 and two channels at 625 GHz) spaceborne instrument for climate research are presented and compared. The optical configurations are analyzed in terms of optical performance (gain, side lobe levels, beam efficiency etc.), weight and size of the overall instrument envelope. Using ideal fundamental Gaussian beam modes and numerical tools relying on ray-tracing and physical optics methods, the different configurations are designed and evaluated. Preliminary results indicate that a 1.3 m x 0.65 m primary reflector can be used in a configuration that includes a relay optics system having two to four elements. In addition to the limb-viewing instrument, there will be an additional instrument operating at 640 GHz for observing clouds in nadir mode

1.6 GHz Low-Power Cross-Correlator System Enabling Geostationary Earth Orbit Aperture Synthesis

We present a 64-channel cross-correlator system for space-borne synthetic aperture imaging. Two different types of ASICs were developed to fit into this system: An 8-channel comparator ASIC implemented in a 130 nm SiGe BiCMOS process technology performs A/D conversion, while a single 64-channel digital cross-correlator ASIC implemented in a 65 nm CMOS process performs the signal processing. The digital ASIC handles 2016 cross-correlations at up to 3.6 GS/s and has a power dissipation of only 0.13 mW/correlation/GHz at a supply voltage of 1 V. The comparator ASIC can handle sample rates of at least 4.5 GS/s with a power dissipation of 47 mW/channel or 1 GS/s with a power dissipation of 17 mW/channel. The assembled system consists of a single board measuring a mere 136 x 136 mm(2) and weighing only 135 g. The assembled system demonstrates crosstalk of 0.04% between neighboring channels and stability of 800 s. We provide ASIC and system-board measurement results that demonstrate that aperture synthesis can be a viable approach for Earth observation from a geostationary Earth orbit

Transient perceptual neglect: visual working memory load affects conscious object processing

Visual working memory (VWM) is a capacity-limited cognitive resource that plays an important role in complex cognitive behaviors. Recent studies indicate that regions subserving VWM may play a role in the perception and recognition of visual objects, suggesting that conscious object perception may depend on the same cognitive and neural architecture that supports the maintenance of visual object information. In the present study, we examined this question by testing object processing under a concurrent VWM load. Under a high VWM load, recognition was impaired for objects presented in the left visual field, in particular when two objects were presented simultaneously. Multivariate fMRI revealed that two independent but partially overlapping networks of brain regions contribute to object recognition. The first network consisted of regions involved in VWM encoding and maintenance. Importantly, these regions were also sensitive to object load. The second network comprised regions of the ventral temporal lobes traditionally associated with object recognition. Importantly, activation in both networks predicted object recognition performance. These results indicate that information processing in regions that mediate VWM may be critical to conscious visual perception. Moreover, the observation of a hemifield asymmetry in object recognition performance has important theoretical and clinical significance for the study of visual neglect

The SKA Particle Array Prototype: The First Particle Detector at the Murchison Radio-astronomy Observatory

We report on the design, deployment, and first results from a scintillation detector deployed at the Murchison Radio-astronomy Observatory (MRO). The detector is a prototype for a larger array -- the Square Kilometre Array Particle Array (SKAPA) -- planned to allow the radio-detection of cosmic rays with the Murchison Widefield Array and the low-frequency component of the Square Kilometre Array. The prototype design has been driven by stringent limits on radio emissions at the MRO, and to ensure survivability in a desert environment. Using data taken from Nov.\ 2018 to Feb.\ 2019, we characterize the detector response while accounting for the effects of temperature fluctuations, and calibrate the sensitivity of the prototype detector to through-going muons. This verifies the feasibility of cosmic ray detection at the MRO. We then estimate the required parameters of a planned array of eight such detectors to be used to trigger radio observations by the Murchison Widefield Array.Comment: 17 pages, 14 figures, 3 table