Accuracy of Shack-Hartmann wavefront sensor using a coherent wound fibre image bundle

Shack-Hartmann wavefront sensors using wound fibre bundles are desired for multi-object adaptive optical systems to provide large multiplex positioned by Starbugs. The use of the large-sized wound fibre bundle provides the exibility to use more sub-apertures wavefront sensor for ELTs. These compact wavefront sensors take advantage of large focal surfaces such as the Giant Magellan Telescope. The focus of this paper is to study the wound fibre image bundle structure defects effect on the centroid measurement accuracy of a Shack-Hartmann wavefront sensor. We use the first moment centroid method to estimate the centroid of a focused Gaussian beam sampled by a simulated bundle. Spot estimation accuracy with wound fibre image bundle and its structure impact on wavefront measurement accuracy statistics are addressed. Our results show that when the measurement signal to noise ratio is high, the centroid measurement accuracy is dominated by the wound fibre image bundle structure, e.g. tile angle and gap spacing. For the measurement with low signal to noise ratio, its accuracy is influenced by the read noise of the detector instead of the wound fibre image bundle structure defects. We demonstrate this both with simulation and experimentally. We provide a statistical model of the centroid and wavefront error of a wound fibre image bundle found through experiment.Comment: 14 pages, 19 figures,5 tables This paper has been accepted for publication in PAS

Characterisation of the Optical Turbulence at Siding Spring

Measurements of the optical turbulence profile above Siding Spring Observatory were conducted during 2005 and 2006. This effort was largely motivated by the need to predict the statistical performance of adaptive optics at Siding Spring. The data were collected using a purpose-built instrument based on the slope-detection and ranging method (SLODAR) where observations of a bright double star are imaged by Shack-Hartmann taken with the Australian National University 24 inch and 40 inch telescopes. The analysis of the data yielded a model consisting of a handful of statistically prominent thin layers that are statistically separated into the ground layer (37.5, 250m) and the free atmosphere (1, 3, 6, 9, 13.5 km) for good (25%), typical (50%) and bad (25%) observing conditions. We found that ground-layer turbulence dominates the turbulence profile with up to 80% of the integrated turbulence below 500 m. The turbulence tends to be non-Kolmogorov, especially for the ground-layer with a power law index of $\beta \sim 10/3$. The mirror/dome seeing can be a significant fraction of the ground-layer turbulence. The median atmospheric seeing, is around 1.2", in agreement with observational reports.Comment: 23 pages; accepted for publication in PAS

Adaptive Optics Simulations for Siding Spring

Using an observational derived model optical turbulence profile (model-OTP) we have investigated the performance of Adaptive Optics (AO) at Siding Spring Observatory (SSO), Australia. The simulations cover the performance for AO techniques of single conjugate adaptive optics (SCAO), multi-conjugate adaptive optics (MCAO) and ground-layer adaptive optics (GLAO). The simulation results presented in this paper predict the performance of these AO techniques as applied to the Australian National University (ANU) 2.3 m and Anglo-Australian Telescope (AAT) 3.9 m telescopes for astronomical wavelength bands J, H and K. The results indicate that AO performance is best for the longer wavelengths (K-band) and in the best seeing conditions (sub 1-arcsecond). The most promising results are found for GLAO simulations (field of view of 180 arcsecs), with the field RMS for encircled energy 50% diameter (EE50d) being uniform and minimally affected by the free-atmosphere turbulence. The GLAO performance is reasonably good over the wavelength bands of J, H and K. The GLAO field mean of EE50d is between 200 mas to 800 mas, which is a noticeable improvement compared to the nominal astronomical seeing (870 to 1700 mas).Comment: 15 pages; accepted for publication in PAS

Consumer Attitudes toward Freshness Indicators on Perishable Food Products

Consumer/Household Economics, Food Consumption/Nutrition/Food Safety,

THE SKY IS FALLING: AN EXAMINATION OF BROILER CONTRACT DESIGN AND GROWER REVENUES

A math program is used to examine an integrators problem of assigning broiler growers into settlement pools. The integrator varies the size and frequency of flock placements by grower ability. This differentiates grower incentives by ability. Which growers receive the strongest incentives depends on amount of excess grow-out capacity.Research Methods/ Statistical Methods,

PRODUCER WELFARE CHANGES FROM MEAT AND POULTRY RECALLS

The number and volume of meat and poultry recalls has increased substantially in recent years. This is likely due to regulatory emphasis on foodborne illness resulting in an increased frequency of testing for pathogens. We use an equilibrium-displacement model to examine the effects of recall costs on the beef, pork, and poultry industries. Results suggest that higher recall costs may have actually increased producer surplus to the broiler industry because of consumer substitution among products and that most losses resulting from recalls are accruing to the beef and pork industries.Agribusiness,

Forest scientists and knowledge transfer: explanations for differences in communication styles

Dieser Beitrag setzt sich mit den Fragen auseinander, in welchen unterschiedlichen Stilen Forstwissenschaftler kommunizieren und wie sich Wissenschaftler mit differierenden Kommunikationsstilen unterscheiden. Dabei wird gezeigt, dass die Wissenschaftler in vier Kommunikationstypen eingeteilt werden können. Wissenschaftler mit diesen unterschiedlichen Kommunikationsstilen unterscheiden sich in ihrer Stellung innerhalb der akademischen Welt und ihren Motiven für Kommunikation. Die Vorstellungen über Medienwirkungen unterscheiden sich nicht zwischen den Wissenschaftlern mit unterschiedlichen Kommunikationsstilen. Eine Third-Person-Wahrnehmung kann eindeutig festgestellt werden, diese hat jedoch keinen Einfluss auf das Kommunikationsverhalten.This article covers the questions how forest scientists communicate in different styles and how scientists with different communication styles vary. Four different types of communicational behaviour are found. Scientists with these different styles of communication differ in their academic status and their motives for communication. The perceptions of media effects don’t differ between the scientists with different communication styles. A third-person-perception is clearly detectable, but it has no effect on the communicational behaviour of scientists

Improved detection of atmospheric turbulence with SLODAR

We discuss several improvements in the detection of atmospheric turbulence using SLOpe Detection And Ranging (SLODAR). Frequently, SLODAR observations have shown strong ground-layer turbulence, which is beneficial to adaptive optics. We show that current methods which neglect atmospheric propagation effects can underestimate the strength of high altitude turbulence by up to ~ 30%. We show that mirror and dome seeing turbulence can be a significant fraction of measured ground-layer turbulence, some cases up to ~ 50%. We also demonstrate a novel technique to improve the nominal height resolution, by a factor of 3, called Generalized SLODAR. This can be applied when sampling high-altitude turbulence, where the nominal height resolution is the poorest, or for resolving details in the important ground-layer