JavaScript Pages for Astronomy, (Astro)Physics, Numerics, Electronics:

Joachim Köppen Kiel 2022

Contents

Introduction This is a collection of JavaScript programs written for teaching, creating exercises, allowing self-study and for use as small research tools. They aim to permit an interactive exploration of the behaviour of physical systems.

All programs work on Chrome, InternetExplorer, Edge, and Firefox (all in Windows10).

As time goes by, more is to come ... :-)

Space Exploration and Solar System

• Two Body Simulation shows the movement of a body in the attractive field of another body, e.g. a planet around the Sun. This is the simple Kepler problem, but done for a general attractive force. This version computes only 1000 time steps at one batch, but it does so quickly!
• Two Body Simulation (start/stop) shows the movement of a body in the attractive field of another body, e.g. a planet around the Sun. This is the simple Kepler problem, but done for a general attractive force. This version is slower, but one can start and stop the simulation ...
• Orbits in a Central Potential shows the movement of a body in the attractive field of another body, e.g. a planet around the Sun or a galaxy about another. This version also allows the use of a variety of computational methods.
• Spaceship in the Earth/Moon system simulates the flight of a spaceship in the combined gravitational field of Earth and Moon, which are orbiting each other. One may compute the flights from Earth to Moon by a fast direct trajectory or via a chaotic orbit in a slow but less expensive way, and study regular and chaotic solutions of the restricted Three Body Problem.
• Perturbation of a Stellar/Planetary Dust Disk by a Planet/Moon shows the how the gravitational attraction by the planet/moon leads to a re-arrangement of the orbits of dust particles, which is quite different from the initial evenly distribution. Due to the perturbations, the planet/moon sweeps clear a region about its own orbit, but also traps particles in horseshoe orbits about its Lagrangean points, and causes the presence of other gaps in the disk. This happened when our Solar System was formed. For instance Jupiter captured the Trojan astroids. Also, the rings around Saturn have been shaped by its moons.
• The Radio Sun shows the brightness profile of the Sun at any wavelength. The emission from photosphere, chromosphere, and corona are computed along several lines of sight across the solar face, taking into account that the path of the radio waves are curved due to the refraction by the plasma of the solar atmosphere.
• Eclipse of the Radio Sun shows how the radio flux observed from the Sun changes during a solar eclipse. The Sun's emission is modelled by the contributions from photosphere/chromosphere, corona, and one active region. The Moon's trajectory and radius can be altered to show total, partial, and annular eclipses.
• Temperatures and Radio Emission of the Lunar Soil shows the variation of the temperatures in the lunar soil due to the illumination by the Sun, during a whole month and during a total lunar eclipse. It also computes the lunar radio flux at various frequencies.
• Brightness Temperature of the Moon shows the monthly variation of the temperature of the Moon predicted for various frequencies from a simple model of the heat transport in the lunar soil. The data can be ouput in the form of a text table. Measured data from professional publications obtained since 1949 are also shown.

Exoplanets

• ExoPlanet Calculator is a simple tool to estimate the characteristics of the transit of an exoplanet which passes across the face of its parent star.

Stars and Nebulae

• Plasma Diagnostics interprets the emission line spectrum of ionized gaseous nebulae: from the observed intensities of the lines, temperature, density, and the abundances of the elements in the nebula are derived. This is a scaled-down version of my professional-level code HOPPLA.
• Solar Photospheric Abundances gives the data from Asplund et al. (2009) in the usual logarithmic values as well as the linear mass fractions. If the user changes one of the values, and hits the return key, all values are recomputed.
• Interstellar Extinction is a small utility that allows the conversion of extinction, optical depth, attenuation for any optical, ultraviolet and infrared wavelength, using various interstellar extinction curves.
• Photometric Colours from Spectra of Single Stars and Stellar Populations computes the spectrum of a stellar population composed of a mixture of main sequence and red giant stars, specified by their contributions, and the resultant photometric colours.
• Photometric Colours from Spectra of Single Stars and Stellar Populations (II) computes the spectrum of a stellar population composed of a mixture of main sequence and red giant stars, specified by their contributions, and the resultant photometric colours. This version also gives the colours in the photometric system of our practise telescope.
• Synthetic Stellar Populations generates a population of stars of different ages and metallicities and computes the distribution in the Hertzsprung-Russell diagram and in Colour-Magnitude and Colour-Colour diagrams.
• Blackbody plots this curve in various ways and displays the integrated energy and photon fluxes.
• Compute the radius and the mass of the Strömgren Sphere around a source of ionizing radiation, given the number of ionizing photons or the temperature and radius of the central star.
• Analysis of an emission nebula assumes the simple model of a Strömgren Sphere to estimate the distance of the object from its observed Hβ flux, angular diametre, and electron density. Also, we get the number of ionizing photons necessary to make the nebula, and the luminosity of the central star.

our Milky Way galaxy

• Radial Velocities in the Galactic Plane shows the radial velocities measured at the position of the Solar System of gas clouds which travel in the plane of the Milky Way on circular orbits around the Galactic Centre.

Galaxies

• Photometric Colours from Spectra of Single Stars and Stellar Populations computes the spectrum of a stellar population composed of a mixture of main sequence and red giant stars, specified by their contributions, and the resultant photometric colours.
• Photometric Colours from Spectra of Single Stars and Stellar Populations (II) computes the spectrum of a stellar population composed of a mixture of main sequence and red giant stars, specified by their contributions, and the resultant photometric colours. This version also gives the colours in the photometric system of our practise telescope.
• Stellar Yields displays the amount of chemical elements (C, N, O, Mg, Fe) produced by fusion inside stars of different masses. Computes also the 'yield' for these elements which an entire single generation of stars provides.
• Synthetic Stellar Populations generates a population of stars of different ages and metallicities and computes the distribution in the Hertzsprung-Russell diagram and in Colour-Magnitude and Colour-Colour diagrams.
• Dark Matter in Galaxy Clusters shows the distribution of dark matter and hot intracluster medium (ICM) in clusters of galaxies, and the circular and escape velocities. It also deduces from an observed ICM distribution the distribution of dark matter, under the assumption of hydrostatic equilibrium.
• A Galaxy's Flight through the Gas in a Galaxy Cluster allows to trace the orbit as well as to compute the history of the ram pressure acting on the galaxy, which is able to strip away the galaxy's interstellar gas.
• My version of the Toomres' simulation of the Collision of Disk Galaxies is available here. The two galaxies are modeled by a number of stellar particles circling the centre in the shape of disks, and during the collision only the tidal forces are taken into account. The user specifies the parameters of the collision course as well as the masses and orientations of the disks. This classical simulation proved that extended arms observed in some galaxies are due to the tidal interaction between the two galaxies.
• Radio Views of a Rotating Galaxy is a simulation of how the rotating gas disk of a spiral galaxy with arbitrary orientation appears to an observer, who cannot have the full 3-D view, but the two dimensional image and the radial velocity information from spectroscopy. It takes into account the finite spatial resolution due to the width of the antenna beam.
• Radio Views of a Rotating Galaxy (Version 2) is a simulation of how the rotating gas disk of a spiral galaxy with arbitrary orientation appears to an observer, who cannot have the full 3-D view, but the two dimensional image and the radial velocity information from spectroscopy. It also allows to compute spectra seen when the antenna is pointed at a given position, and to create spectra when the galaxy is covered by a square grid of antenna positions. The numerical data can be obtained by copy&paste.
• Radio Views of a Rotating Galaxy (Version F1EHN) is a simulation of how the rotating gas disk of a spiral galaxy with arbitrary orientation appears to an observer, who cannot have the full 3-D view, but the two dimensional image and the radial velocity information from spectroscopy. It also allows to compute spectra seen when the antenna is pointed at a given position, and to create spectra when the galaxy is covered by a square grid of antenna positions. The numerical data can be obtained by copy&paste. This version also contains the spectra for M31 and M33 observed by F1EHN
• View of a Galaxy with a Gas Tail allows to make false colour images indicating the gas surface density seen from a galaxy and its gas tail. The tail is modeled by a simple cylindrical sheet of gas, whose geometry is specified by parameters, and the object can be viewed from various angles.

more Astrophysics

• Orbits in a Central Potential shows the movement of a body in the attractive field of another body, e.g. a planet around the Sun or a galaxy about another. This version also allows the use of a variety of computational methods.
• The Onedimensional Hydrodynamics simulation shows how the gas which had initially been confined to the left part in a tube, fills the entire volume, once its partition is opened; the formation of a shock and a rarefaction wave can be followed. Both the isothermal and the adiabatic case can be done. The hydrodynamical equations are discretized on a equidistant spatial grid, and are solved with an explicit method.
• The Smoothed Particle Hydrodynamics simulation shows how the gas which had initially been confined to the left part in a tube, fills the entire volume, once its partition is opened; the formation of a shock and a rarefaction wave can be followed. In SPH simulations the gas is represented by a number of particles, which move in such a way that quantities like density and velocity behave as described by the hydrodynamic equations.
• Blackbody plots this curve in various ways and displays the integrated energy and photon fluxes.

RadioAstronomy

• Radio sources in the sky shows the radio fluxes for well-known sources, and - given the effective antenna diameter and the system temperature - displays the antenna temperature and the expected signal to noise ratio.
• Atmospheric Attenuation computes for a given radio frequency, atmospheric temperature, pressure, and humidity the attenuation by the Earth atmosphere at zenith and a given elevation angle. This is done with the approximate formulae from ITU Recommendation P.676-10 (09/2013, Appendix 2) for frequencies between 1 and 350 GHz.
• Sky Profile Analysis Measurements of the noise of the empty sky at several different elevation angles can be used to determine the actual attenuation by the Earth atmosphere above a station, as well as the noise figure (or system temperature) of its receiving system. Given the measurements of the sky and the ground noise, this tool finds in an automatic way the values of the two parameters which provide a best fit to the data.
• Measures of the noise at Sun Moon & Ground along with the empty sky gives three estimates for the system temperature. Significant differences between the values are a sign for errors in some of the measured values, which indicates that the measuring methods or/and equipment need revision or improvement. If the three values agree with each other, they very likely indicate the true noise figure of the receiving system of antenna and receiver. This 'overall' noise figure includes also how much noise from the surroundings is picked up by the antenna's side and rear lobes. It thus gives an indication for the true efficiency of the antenna. Knowing this better helps in optimizing the antenna system.
• Parameters of Aperture Antennas computes the gain, half-power beam width, effective area and other parameters of circular antennas, as well as the antenna temperature and signal to noise ratio for a source of given radio flux and with specified system temperature.
• Antenna Patterns are computed for square and circular aperture antennas, either uniformly illuminated or with a few laws. This is done for a point source, which reveals the theoretical pattern, as well as for extended sources of specified angular diameter and with a few simple surface brightness distributions.
• Phased Square Aperture computes the patterns of square aperture antennas, illuminated in different ways in amplitude and phase.
• Performance of Parabolic Dish Antennas is computed for illumination by various feeds. The feed pattern, the antenna efficiency, spillover losses and illumination losses, and the resulting antenna radiation pattern are calculated for dishes with specified f/D ratio of focal length and diameter.
• Antenna Spill-Over computes from measurements of the sky noise at various elevations the system temperature of the radio telescope and the zenith temperature for the thermal emission of the Earth atmosphere. It then allows the user to add spill-over noise to account for the enhanced sky noise measured at elevations close to the zeinth. In this way, one can measure the spill-over contribution to the system noise.
• Filling Factors are the fraction of the antenna beam that is filled with the radiation of the source, and gives the ratio of antenna and brightness temperatures. This factor depends on the shapes of the antenna lobe and the source brightness pattern and on the ratio of their respective sizes. The tool computes and display filling factor functions for circular antenna beams with various antenna patterns and circular disc sources, including those with limb darkening or limb brightening. The user may download numerical tables of these functions.
• The relation between Gain and HPBW is independent of frequency. Here is a simple plot of this relation for uniformly illuminated dish antennas.
• The GroundNoise which an antenna picks up is partly thermal radiation from the soil and partly reflected noise from the sky. This is computed for different angles, frequencies, and properies of the ground material.
• For Scheduling Observations one needs to know when a celestial source stays above the horizon for a desired duration. This is done for the Sun, Moon, or celestial sources given by galactic or equatorial coordinates, for any geographical location, and time (UT or local sideral time).
• RoenneRadioMeter is a simulator for observations at 1304 MHz with the 9m parabolic antenna of DL0SHF in Rönne. Its graphical user interface, its controls, and their behaviour are very similar to the software used on the real instrument. It allows realistic measurements of the Sun, Moon, and other celestial sources and produces realistic data in the same format as the real software. Furthermore it allows to set freely the time of observation.
• RoenneSpectroMeter is a simulator for observations in the 21 cm line of neutral hydrogen with the 9m parabolic antenna of DL0SHF in Rönne. Its graphical user interface, its controls, and their behaviour resemble closely the software used on the real instrument. It allows realistic measurements of the positions in the Galactic Plane (based on real measurements using this antenna), and also continuum measurements of the Sun, Moon, and other celestial sources. The realistic data are in the same format as from the real software. Furthermore one may freely set the time of observation.
• RoenneRadioMeter (Version CMB) is a simulator for observations at 1304 MHz with a parabolic dish antenna (like the 9m parabolic antenna of DL0SHF in Rönne), which also includes the direct calibration by placing an absorbing body of known temperature in front of the feed antenna. Although this technique is not feasible in the real instrument, its simulation allows the user to evaluate and practise how one determines the temperature of the Cosmic Microwave Background. Note that for this task the results are independent of the diameter of the antenna.
• Simple Radio Interferometer computes the relative power measured by either a single radio telescope or an interferometer with 2 or 3 antennas, when one of a few simple radio sources pass over the instrument. One can choose the frequency, antenna diameter, separation of the antennas, the angular size of a single source and the separation and brightness ratio of a pair of sources. For computational convenience, the simulation is restricted to one angular dimension, so that the source travels straight through the centre of the optical axis of the instrument. But this allows to capture the principal features of observing with an interferometer. The data can be outputted in numerical form for further analysis by the user.
• Radio Views of a Rotating Galaxy is a simulation of how the rotating gas disk of a spiral galaxy with arbitrary orientation appears to an observer, who cannot have the full 3-D view, but the two dimensional image and the radial velocity information from spectroscopy. It takes into account the finite spatial resolution due to the width of the antenna beam.
• Radio Views of a Rotating Galaxy (Version 2) is a simulation of how the rotating gas disk of a spiral galaxy with arbitrary orientation appears to an observer, who cannot have the full 3-D view, but the two dimensional image and the radial velocity information from spectroscopy. It also allows to compute spectra seen when the antenna is pointed at a given position, and to create spectra when the galaxy is covered by a square grid of antenna positions. The numerical data can be obtained by copy&paste.
• The Radio Sun shows how the brightness profile of the Sun at any wavelength is calculated by integrating the emissions from photosphere, chromosphere, and corona along several lines of sight across the solar face, taking into account that the path of the radio waves are curved due to the refraction by the plasma of the solar atmosphere.
• The Solar Radio Profiles shows the brightness profile of the Sun at any wavelength, interpolated from computations by Waldmeier & Müller (1948, 1950) and Smerd (1950). Also is displayed how a drift scan across the Sun looks like, as done with an antenna of specified beam width.
• Eclipse of the Radio Sun shows how the radio flux observed from the Sun changes during a solar eclipse. The Sun's emission is modelled by the contributions from photosphere/chromosphere, corona, and one active region. The Moon's trajectory and radius can be altered to show total, partial, and annular eclipses.
• Temperatures and Radio Emission of the Lunar Soil shows the variation of the temperatures in the lunar soil due to the illumination by the Sun, during a whole month and during a total lunar eclipse. It also computes the lunar radio flux at various frequencies.
• Brightness Temperature of the Moon shows the monthly variation of the temperature of the Moon predicted for various frequencies from a simple model of the heat transport in the lunar soil. The data can be ouput in the form of a text table. Measured data from professional publications obtained since 1949 are also shown.
• Lunar Radio Images shows the distribution of radio brightness on the face of the Moon predicted for any frequency and lunar phase computed with the above simple model for the heat transport in the lunar soil.
• Lunar Radio Images (Version II) shows the distribution of radio brightness on the face of the Moon predicted for any frequency and lunar phase computed with the above simple model for the heat transport in the lunar soil. In this version one may also look at the radio Moon, as it is blurred by the finite width of the beam of an radio antenna.
• Lunar Drift Scans computes and display the results of letting the radio Moon drift through the antenna beam of a radio telescope.
• Aim at the Radio Moon computes and displays the radio image of the Moon in the proper orientation with respect to the local horizon, for any location, date and time, and frequency. One may also view the image as it is blurred by the finite width of the radio telescope's beam.

Interferometry

• KURT = Kiel's Universal Radio Telescope is a simulator on any frequencies between about 100 MHz and 350 GHz. It can be used as a single paraboloidal dish of any diameter (larger than 10 wavelengths ... and with a smallest beam width of about 0.01°). As an interferometer it can work with 2 antennas or up to 256 separations of antennas that are positioned along the East-West direction. The instrument's sensitivity is like what one could expect if it were constructed from freely available apparatus and electronic components. Its behaviour is modelled in a realistic manner, the measurements of Sun, Moonm other celestial sources, and the atmospheric foreground yield realistic data. For tests and the planning of observations it can be set to arbitrary times.
• InterferometerExplorer is a tool to show the results of interferometric observations done with systems whose properties may be freely chosen, in order to get the impressions of results under ideal conditions. In this manner, the most suitable configuration of the interferometer can be found to achieve the desired data quality. Also, one may explore and test the basic operations of an interferometer and the dependence on the system properties.
• Simple Radio Interferometer computes the relative power measured by either a single dish radio telescope or an interferometer with 2 or 3 antennas, when a simple radio source pass over the instrument. One can choose the frequency, antenna diameter, separation of the antennas, the angular size of a single source and the separation and brightness ratio of a pair of sources. For computational convenience, the simulation is restricted to one angular dimension, so that the source travels straight through the centre of the optical axis of the instrument. But this allows to capture the principal features of observing with an interferometer. The data can be outputted in numerical form for further analysis by the user.

Observation and Instruments

• Local Sidereal Time is a clock which shows the current UTC and local sidereal time for any location.
• Sun and Moon Position computes for any time and location the positions in the sky of the Sun and the Moon, both in celestial and horizontal coordinates, their angular diameters, the lunar phase and radio flux.
• For Scheduling Observations one needs to know when a celestial source stays above the horizon for a desired duration. This is done for the Sun, Moon, or celestial sources given by galactic or equatorial coordinates, for any geographical location, and time (UT or local sidereal time).
• Airglow Spectrum depicts a typical observed optical spectrum of the night sky; this must always be subtracted from the raw observational data of a star, nebula or galaxy before one gets its true spectrum.
• Coordinate conversion allows to change between azimuth/elevation, right ascension/declination, ecliptical and galactic coordinates.
• If a celestial source has Position Errors in right ascension and declination, the observed position in the sky shows offsets in azimuth and elevation which depend on the sky position. This is shown to aid the determination of the RaDec errors from the observed tracking errors of the source.
• Parameters of Aperture Antennas computes the gain, half-power beam width, effective area and other parameters of circular antennas, as well as the antenna temperature and signal to noise ratio for a source of given radio flux and with specified system temperature.
• Measures of the noise at Sun Moon & Ground along with the empty sky gives three estimates for the system temperature. Significant differences between the values are a sign for errors in some of the measured values, which indicates that the measuring methods or/and equipment need revision or improvement. If the three values agree with each other, they very likely indicate the true noise figure of the receiving system of antenna and receiver. This 'overall' noise figure includes also how much noise from the surroundings is picked up by the antenna's side and rear lobes. It thus gives an indication for the true efficiency of the antenna. Knowing this better helps in optimizing the antenna system.
• Antenna Patterns are computed for square and circular aperture antennas, either uniformly illuminated or with a few laws. This is done for a point source, which reveals the theoretical pattern, as well as for extended sources of specified angular diameter and with a few simple surface brightness distributions.
• Antenna Patterns with Shadowing by the Feed are computed for square and circular aperture antennas, which are uniformly illuminated except for a central region shadowed by the apparatus in the focal point. This is done for a point source, which reveals the theoretical pattern, as well as for extended sources of specified angular diameter and with a few simple surface brightness distributions.
• Performance of Parabolic Dish Antennas is computed for illumination by various feeds. The feed pattern, the antenna efficiency, spillover losses and illumination losses, and the resulting antenna radiation pattern are calculated for dishes with specified f/D ratio of focal length and diameter.
• Antenna Spill-Over computes from measurements of the sky noise at various elevations the system temperature of the radio telescope and the zenith temperature for the thermal emission of the Earth atmosphere. It then allows the user to add spill-over noise to account for the enhanced sky noise measured at elevations close to the zeinth. In this way, one can measure the spill-over contribution to the system noise.
• Blurring of an Object by a Telescope The apparent angular diameter of a (sky) object depends on the angular resolution of the observing instrument. When the instrumental profile - such as the beam width of a radio telescope - is comparable to the size of the object, the object appears to be somewhat larger than it truly is. This one-dimensional simulation allows to explore this effect for various simple objects and for various instrumental profiles.
• Filling Factors are the fraction of the antenna beam that is filled with the radiation of the source, and gives the ratio of antenna and brightness temperatures. This factor depends on the shapes of the antenna lobe and the source brightness pattern and on the ratio of their respective sizes. The tool computes and display filling factor functions for circular antenna beams with various antenna patterns and circular disc sources, including those with limb darkening or limb brightening. The user may download numerical tables of these functions.
• Simple Radio Interferometer computes the relative power measured by either a single radio telescope or an interferometer with 2 or 3 antennas, when one of a few simple radio sources pass over the instrument. One can choose the frequency, antenna diameter, separation of the antennas, the angular size of a single source and the separation and brightness ratio of a pair of sources. For computational convenience, the simulation is restricted to one angular dimension, so that the source travels straight through the centre of the optical axis of the instrument. But this allows to capture the principal features of observing with an interferometer. The data can be outputted in numerical form for further analysis by the user.
• RoenneRadioMeter is a simulator for observations at 1304 MHz with the 9m parabolic antenna of DL0SHF in Rönne. Its graphical user interface, its controls, and their behaviour are very similar to the software used on the real instrument. It allows realistic measurements of the Sun, Moon, and other celestial sources and produces realistic data in the same format as the real software. Furthermore it allows to set freely the time of observation.
• RoenneSpectroMeter is a simulator for observations in the 21 cm line of neutral hydrogen with the 9m parabolic antenna of DL0SHF in Rönne. Its graphical user interface, its controls, and their behaviour resemble closely the software used on the real instrument. It allows realistic measurements of the positions in the Galactic Plane (based on real measurements using this antenna), and also continuum measurements of the Sun, Moon, and other celestial sources. The realistic data are in the same format as from the real software. Furthermore one may freely set the time of observation.
• RoenneRadioMeter (Version CMB) is a simulator for observations at 1304 MHz with a parabolic dish antenna (like the 9m parabolic antenna of DL0SHF in Rönne), which also includes the direct calibration by placing an absorbing body of known temperature in front of the feed antenna. Although this technique is not feasible in the real instrument, its simulation allows the user to evaluate and practise how one determines the temperature of the Cosmic Microwave Background. Note that for this task the results are independent of the diameter of the antenna.
• Sky Profile Analysis (for frequencies below 10 GHz) allows to separate and determine the level of the electronic noise of the receiver of a radio telescope (the system temperature) and the level of the foreground by the Earth atmosphere's thermal emission (zenith temperature) from the measurements of the noise level of the empty sky taken at several elevations. The results are reliable for low atmospheric absorption only, hence for low frequencies.
• Sky Profile Analysis Measurements of the noise of the empty sky at several different elevation angles can be used to determine the actual attenuation by the Earth atmosphere above a station, as well as the noise figure (or system temperature) of its receiving system. Given the measurements of the sky and the ground noise, this tool finds in an automatic way the values of the two parameters which provide a best fit to the data.
• Aim at the Radio Moon computes and displays the radio image of the Moon in the proper orientation with respect to the local horizon, for any location, date and time, and frequency. One may also view the image as it is blurred by the finite width of the radio telescope's beam.

Amateur Radio and Earth-Moon-Earth Communication (EME)

• Aim at the Radio Moon computes and displays the radio image of the Moon in the proper orientation with respect to the local horizon, for any location, date and time, and frequency. One may also view the image as it is blurred by the finite width of the radio telescope's beam.
• Lunar reflectivity shows for any frequency how the reflectivity of the lunar disc varies from the centre to the rim. This is done by an image of the Moon and a plot of the relative reflectivity as a function of radius. The results from radar measurements are interpolated to any frequency.
• Two Narrow Beams on the Moon When EME operations are done with large antennas and/or at high frequencies, the antenna beams may become comparable to the angular size of the Moon, or even smaller. Then the strength of the reflected signal depends on the widths of transmitting and receiving beams, as well as on their positions on the lunar disc. This tool computes and displays the illumination of the Moon's face by the transmitting antenna, the overlap of the two antenna beams, and the correction factor for EME link budget. It also computes the offset loss which occurs when the two beams are not directed to the same spot.
• Lunar Radio Images shows the distribution of radio brightness on the face of the Moon predicted for any frequency and lunar phase computed with the above simple model for the heat transport in the lunar soil.
• Lunar Radio Images (Version II) shows the distribution of radio brightness on the face of the Moon predicted for any frequency and lunar phase computed with the above simple model for the heat transport in the lunar soil. In this version one may also look at the radio Moon, as it is blurred by the finite width of the beam of an radio antenna.
• Lunar Drift Scans computes and display the results of letting the radio Moon drift through the antenna beam of a radio telescope.
• Atmospheric Attenuation computes for a given radio frequency, atmospheric temperature, pressure, and humidity the attenuation by the Earth atmosphere at zenith and a given elevation angle. This is done with the approximate formulae from ITU Recommendation P.676-10 (09/2013, Appendix 2) for frequencies between 1 and 350 GHz.
• Sky Profile Analysis Measurements of the noise of the empty sky at several different elevation angles can be used to determine the actual attenuation by the Earth atmosphere above a station, as well as the noise figure (or system temperature) of its receiving system. Given the measurements of the sky and the ground noise, this tool finds in an automatic way the values of the two parameters which provide a best fit to the data.
• Measures of the noise at Sun Moon & Ground along with the empty sky gives three estimates for the system temperature. Significant differences between the values are a sign for errors in some of the measured values, which indicates that the measuring methods or/and equipment need revision or improvement. If the three values agree with each other, they very likely indicate the true noise figure of the receiving system of antenna and receiver. This 'overall' noise figure includes also how much noise from the surroundings is picked up by the antenna's side and rear lobes. It thus gives an indication for the true efficiency of the antenna. Knowing this better helps in optimizing the antenna system.

Other Stuff ....

Statistics Simulations

Numerical Techniques

Radio and Electronics

• Parameters of Aperture Antennas computes the gain, half-power beam width, effective area and other parameters of circular antennas, as well as the antenna temperature and signal to noise ratio for a source of given radio flux and with specified system temperature.
• Antenna Patterns are computed for square and circular aperture antennas, either uniformly illuminated or with a few laws. This is done for a point source, which reveals the theoretical pattern, as well as for extended sources of specified angular diameter and with a few simple surface brightness distributions.
• Crystal Ladder Bandpass Filters computes from the measured quartz parameters the necessary shunt capacitors, and the frequency response curve.
• Design of Interdigital Bandpass Filters computes the mechanical details of filters of specified design parameters, and shows the resulting frequency response.
• Design of Active Low and Highpass Filters computes the resistor and capacitor values for sections using operational amplifiers and shows the resulting frequency response.

last update: May 2024 J.Köppen