A two-band approach to nλ\lambda phase error corrections with LBTI's PHASECam

PHASECam is the Large Binocular Telescope Interferometer's (LBTI) phase sensor, a near-infrared camera which is used to measure tip/tilt and phase variations between the two AO-corrected apertures of the Large Binocular Telescope (LBT). Tip/tilt and phase sensing are currently performed in the H (1.65 $\mu$m) and K (2.2 $\mu$m) bands at 1 kHz, and the K band phase telemetry is used to send tip/tilt and Optical Path Difference (OPD) corrections to the system. However, phase variations outside the range [-$\pi$, $\pi$] are not sensed, and thus are not fully corrected during closed-loop operation. PHASECam's phase unwrapping algorithm, which attempts to mitigate this issue, still occasionally fails in the case of fast, large phase variations. This can cause a fringe jump, in which case the unwrapped phase will be incorrect by a wavelength or more. This can currently be manually corrected by the observer, but this is inefficient. A more reliable and automated solution is desired, especially as the LBTI begins to commission further modes which require robust, active phase control, including controlled multi-axial (Fizeau) interferometry and dual-aperture non-redundant aperture masking interferometry. We present a multi-wavelength method of fringe jump capture and correction which involves direct comparison between the K band and currently unused H band phase telemetry.Comment: 17 pages, 10 figure

Schooling federalism: evaluating the options for reform

The most efficient way to run, fund and regulate primary and secondary schools in Australia is for the State and Territory Governments to have sole responsibility. Background Australian federalism has evolved significantly since Federation in 1901. There is now extensive, contested concurrency in Commonwealth and State or Territory government roles and responsibilities, particularly in the schooling portfolio, where it has effectively moved from being a state responsibility to a shared responsibility. The degree of national government involvement in schooling is unprecedented and higher than that of any other federal government in the world. Uncoordinated decision-making, a mismatch in revenue versus responsibilities, and unhelpful overlap in some roles has contributed to the exacerbation of disadvantage and inequities, limiting the effectiveness of government funding and programs. This poses dire consequences for individual students and the nation. This change was not by design. But its reform can be. The White Paper on the Reform of the Federation was established to investigate federalism reform in a range of portfolios characterised by complex, counterproductive and inconsistent government roles; propose and consult on a range of reform options; and set out a platform for improvement. It is led by a Taskforce located within the Prime Minister’s department, overseen by an intergovernmental steering committee and expert advisory panel. Evaluating the options for reform In June 2015, four options for reform to government roles and responsibilities in the schooling portfolio were leaked and later publicly released by the Taskforce. These options were the product of discussions with stakeholders, all the States and Territories, and the Prime Minister’s Expert Advisory Panel. 1. States and Territories fully responsible for all schools 2. States and Territories responsible for funding public schools and the Commonwealth responsible for funding nongovernment schools. States remain responsible for delivery education in government schools and the regulatory framework for all schools. 3. Reduced Commonwealth involvement in school programs 4. The Commonwealth is the dominant funder of all students on an equal and consistent basis, but States and Territories maintain other current responsibilities, including regulatory framework and provision of public schools. The reform plan put forward by the Taskforce in the final White Paper must be within the current constitutional framework (meaning constitutional change is not required). Purpose of this paper This paper evaluates these four options against the criteria established by Australia’s governments. It also considers the feasibility and desirability of each option. In doing so, it seeks to enhance understanding of federalism in schooling, and to contribute to public debate on the reform options under consideration by the leaders of Australia’s governments

Towards controlled Fizeau observations with the Large Binocular Telescope

The Large Binocular Telescope Interferometer (LBTI) can perform Fizeau interferometry in the focal plane, which accesses spatial information out to the LBT's full 22.7-m edge-to-edge baseline. This mode has previously been used to obtain science data, but has been limited to observations where the optical path difference (OPD) between the two beams is not controlled, resulting in unstable fringes on the science detectors. To maximize the science return, we are endeavoring to stabilize the OPD and tip-tilt variations and make the LBTI Fizeau mode optimized and routine. Here we outline the optical configuration of LBTI's Fizeau mode and our strategy for commissioning this observing mode.Comment: 15 pages, 7 figures, to appear in the Proceedings of the SPIE (SPIE Astronomical Telescopes + Instrumentation 2018; Optical and Infrared Interferometry and Imaging VI

Finite energy coordinates and vector analysis on fractals

We consider (locally) energy finite coordinates associated with a strongly local regular Dirichlet form on a metric measure space. We give coordinate formulas for substitutes of tangent spaces, for gradient and divergence operators and for the infinitesimal generator. As examples we discuss Euclidean spaces, Riemannian local charts, domains on the Heisenberg group and the measurable Riemannian geometry on the Sierpinski gasket

Energy measure closability for Dirichlet forms

We consider symmetric Dirichlet forms on locally compact and non-locally compact spaces and provide an elementary proof for their closability with respect to energy dominant measures. We also discuss how to use known potential theoretic results to furnish an alternative proof of this theorem