Fringe Visibility Estimators for the Palomar Testbed Interferometer

Visibility estimators and their performance are presented for use with the Palomar Testbed Interferometer (PTI). One operational mode of PTI is single-baseline visibility measurement using pathlength modulation with synchronous readout by a NICMOS-3 infrared array. Visibility is estimated from the fringe quadratures, either incoherently, or using source phase referencing to provide a longer coherent integration time. The visibility estimators differ those used with photon-counting detectors in order to account for biases attributable to detector offsets and read noise. The performance of these estimators is affected not only by photon noise, but also by the detector read noise and errors in estimating the bias corrections, which affect the incoherent and coherent estimators differently. Corrections for visibility loss in the coherent estimators using the measured tracking jitter are also presented.Comment: PASP in press (Jan 99). 13 Pages, no figure

Mars Activities: Teacher Resources and Classroom Activities

This set of classroom activities presents the challenges of operating a planetary rover, how to construct a scale model of the Earth-Moon system, how Martian surface core samples can be identified and what they tell us about Mars. Each activity comes with clearly delineated instructions, associated standards, guides and worksheets, and enhancement materials. Educational levels: High school, Intermediate elementary, Middle school, Primary elementary

Least-action perihelion precession

The precession of Mercury's perihelion is reinspected by the principle of least action. The anomalous advancement of the apside line that is customarily accounted by the theory of general relativity, is ascribed to the gravitational effect due to the entire Universe. When the least action is written in the Sun's frame of reference, the residual rotation is seen to stem from inertia due to all bodies in the Universe. Since mass corresponds to a bound form of energy, gravity, as any other force, can be described as an energy density difference between a system of bodies and its surrounding energy densities that are dispersed throughout the Universe. According to the principle of least action the Universe is expanding by combustion of mass to radiation in the quest of equilibrating the bound forms of energy with "zero-density surroundings" in least time. Keywords: cosmological principle; energy density; energy dispersal; evolution; gravity; the principle of least actionComment: 7 pages, 3 figure

Application of Correct-by-Construction Principles for a Resilient Risk-Aware Architecture

In this paper we discuss the application of correct-by-construction techniques to a resilient, risk-aware software architecture for onboard, real-time autonomous operations. We mean to combat complexity and the accidental introduction of bugs through the use of verifiable auto-coding software and correct-by-construction techniques, and discuss the use of a toolbox for correct-by-construction Temporal Logic Planning (TuLiP) for such a purpose. We describe some of TuLiP’s current functionality, specifically its ability to model symbolic discrete systems and synthesize software controllers and control policies that are correct-by-construction. We then move on to discuss the use of these techniques to define a deliberative goal-directed executive capability that performs risk-informed action-planning – to satisfy the mission goals (specified by mission control) within the specified priorities and constraints. Finally, we discuss an application of the TuLiP process to a simple rover resilience scenario

Voyager at Neptune

https://digitalcommons.cwu.edu/government_posters/1167/thumbnail.jp

Voyager: A Journey to the Outer Planets

https://digitalcommons.cwu.edu/government_posters/1166/thumbnail.jp

Solar-Terrestrial Environment

https://digitalcommons.cwu.edu/government_posters/1169/thumbnail.jp

Solar wind channels for MeV particles

Plasma, magnetic field and charged particle data from the Ulysses spacecraft is used to demonstrate that MeV particles follow channels defined by solar wind flow regimes