Krzysztof Bernacki

BRITE Constellation: data processing and photometry

The BRITE mission is a pioneering space project aimed at the long-term photometric monitoring of the brightest stars in the sky by means of a constellation of nano-satellites. Its main advantage is high photometric accuracy and time coverage inaccessible from the ground. The main aim of this paper is the presentation of procedures used to obtain high-precision photometry from a series of images acquired by the BRITE satellites in two modes of observing, stare and chopping. We developed two pipelines corresponding to the two modes of observing. The assessment of the performance of both pipelines is presented. It is based on two comparisons, which use data from six runs of the UniBRITE satellite: (i) comparison of photometry obtained by both pipelines on the same data, which were partly affected by charge transfer inefficiency (CTI), (ii) comparison of real scatter with theoretical expectations. It is shown that for CTI-affected observations, the chopping pipeline provides much better photometry than the other pipeline. For other observations, the results are comparable only for data obtained shortly after switching to chopping mode. Starting from about 2.5 years in orbit, the chopping mode of observing provides significantly better photometry for UniBRITE data than the stare mode. This paper shows that high-precision space photometry with low-cost nano-satellites is achievable. The proposed meth- ods, used to obtain photometry from images affected by high impulsive noise, can be applied to data from other space missions or even to data acquired from ground-based observations.

The influence of the properties of magnetic materials on a voltage source inverter control

Magnetic materials made of iron-powder that are used for the cores of the chokes of voltage source inverters output filters significantly change their power losses and magnetic properties with the frequency and the amplitude of the choke current in the range that is important for designers. This causes the magnitude Bode plot of the VSI control transfer function to have a higher damping coefficient and the resonant frequency that differs from the theoretically calculated one. The paper shows the influence of the properties of magnetic materials on the control of a voltage source inverter. The design of the control loop that takes into account the changes in these properties is presented and tested in the experimental model.

The dynamic properties of a single-phase transformer-based inverter for ups systems

This paper presents two algorithms for the creation of an analytical model of a single-phase transformer-based inverter, using either the measurements of the control frequency-dependent characteristics of the inverter or the initial in-circuit frequency-dependent measurements of the transformer. The paper discusses how the parameters of the line transformer influence the dynamic properties of the inverter and, as a consequence, the design of the instantaneous control feedback loop. Line transformers, widely used in industry, have not yet been analysed for use at higher than normal operating frequencies. The basic parameters of the transformer are the nonlinear functions of the primary voltage amplitude and frequency. The paper includes verification of both methods using the breadboard experimental model. In the final step, the inverter control transfer functions are calculated. To show the utility of both models, an exemplary discrete controller for the experimental inverter model has been designed and tested. Copyright

Review of Image Quality Measures for Solar Imaging

Observations of the solar photosphere from the ground encounter significant problems caused by Earth’s turbulent atmosphere. Before image reconstruction techniques can be applied, the frames obtained in the most favorable atmospheric conditions (the so-called lucky frames) have to be carefully selected. However, estimating the quality of images containing complex photospheric structures is not a trivial task, and the standard routines applied in nighttime lucky imaging observations are not applicable. In this paper we evaluate 36 methods dedicated to the assessment of image quality, which were presented in the literature over the past 40 years. We compare their effectiveness on simulated solar observations of both active regions and granulation patches, using reference data obtained by the Solar Optical Telescope on the Hinode satellite. To create images that are affected by a known degree of atmospheric degradation, we employed the random wave vector method, which faithfully models all the seeing characteristics. The results provide useful information about the method performances, depending on the average seeing conditions expressed by the ratio of the telescope’s aperture to the Fried parameter, D/r0

NIR finger vascular system imaging in angiology applications

D/r_{0}

A Passive FPAA-Based RF Scatter Meteor Detector

. The comparison identifies three methods for consideration by observers: Helmli and Scherer’s mean, the median filter gradient similarity, and the discrete cosine transform energy ratio. While the first method requires less computational effort and can be used effectively in virtually any atmospheric conditions, the second method shows its superiority at good seeing (D/r0<4

Drawbacks of impedance networks

D/r_{0}<4

Influence of Z-source output impedance on dynamic properties of single-phase voltage source inverters for uninterrupted power supply

). The third method should mainly be considered for the post-processing of strongly blurred images.

Different approaches to modelling single-phase voltage source inverters for uninterruptible power supply systems

Nowadays, in the age of technological development in various areas of life there is a growing interest in non-invasive techniques useful in medical examination. Angiology also called vascular medicine is a medical specialty with interest of diseases and disabilities of the human circulatory system. This domain uses different types of imaging. The acquired images are used for research, diagnostic, therapeutic or educational purposes. Different wavelengths and frequencies are used in the design of medical apparatus. In this paper the usability of near infrared light imaging is discussed and case studies of medical examinations are presented. There is a new approach with range area of applications in angiology.

Electromagnetic compatibility of voltage source inverters for uninterruptible power supply system depending on the pulse-width modulation scheme

In the article we present a hardware meteor detector. The detection principle is based on the electromagnetic wave reflection from the ionized meteor trail in the atmosphere. The detector uses the ANADIGM field programmable analogue array (FPAA), which is an attractive alternative for a typically used detecting equipment - a PC computer with dedicated software. We implement an analog signal path using most of available FPAA resources to obtain precise audio signal detection. Our new detector was verified in collaboration with the Polish Fireball Network - the organization which monitors meteor activity in Poland. When compared with currently used signal processing PC software employing real radio meteor scatter signals, our low-cost detector proved to be more precise and reliable. Due to its cost and efficiency superiority over the current solution, the presented module is going to be implemented in the planned distributed detectors system.