Inhalt

Abstract:

Within only a few decades in the 19th century, radio astronomy has rapidly gained high importance within astronomy. Especially the use of radio telescope arrays, along with the dramatically increased possibilities of information technology, has enabled a variety of ambitious and forward-looking projects which delivered spectacular results. Recent examples are the most detailed image ever of the Galactic Center with MeerKAT, a pilot project of the international Square Kilometer Array (SKA), or the first image of the shadow of a black hole by the global Event Horizon Telescope (EHT). Other selected important examples for radio telescope arrays are the Atacama Large Millimeter/submillimeter Array (ALMA) and the European Low-Frequency Array (LOFAR). The basis for all these measurements is radio interferometry, which also plays an important role for geodesy, since it allows high-precision measurements of the position and orientation of Earth in space. For this purpose, three radio telescopes are operated by the Bundesamt für Kartographie and TUM in Wettzell in the Bavarian Forest. Radio interferometry is a complex technique on a mathematical, information technological and physical level. Understanding radio-interferometric methods is also of interest to computer scientists who want to gain experience in the field of big data, since the next generation of radio interferometers, e.g., LOFAR and SKA, generate data amounts in the range of several 100 petabytes per day which corresponds to the entire amount of data stored by Google, Facebook and Microsoft together.

In this course students will learn the mathematical and theoretical basics of radio interferometry. Furthermore, students will gain knowledge of basic radio interferometric methods using examples from modern astronomy and current measurements from radio astronomical interferometers. The students will acquire the following skills: Understanding of the concept of interferometric observations and their calibration, processing and interpretation of raw data, data reduction, data analysis, application and understanding of established algorithms and handling large amounts of data. During practical exercises the students will learn how to reconstruct images from radio interferometrical data.

Gliederung:

Chapter 1 - Motivation and Background:

   1) History of radio astronomy;
   2) The role and development of radio interferometry;
   3) Applications of radio interferometry and scientific topics of special interest

Chapter 2 - Fundamental Concepts:
   1) Fourier optics:
      a) The concept of telescope aperture;
      b) Convolution and Fourier Theorems;
      c) (Radio) telescopes as spatial filters;
   2) Interefrometry:
      a) The Michelson interferometer;
      b) The two-element interferometer;
      c) The visibility function;
      d) The influence of limited bandwidth;
      e) Spatial frequencies in interferometry;
      f) Coordinate systems;
   3) Aperture Synthesis by Radio Interferometric Arrays:
      a) The concept of (u,v) coverage;
      b) Simple configurations and transit arrays;
      c) Tracking arrays;
      d) VLBI arrays;
      e) Antenna separations and geometry;
   4) Receiver Response:
      a) Heterodyne frequency conversion;
      b) Interferometer sensitivity;
      c) Sampling, weighting, gridding;
      d) Bandwidth smearing;
      e) Calibration;
   5) Image reconstruction:
      a) CLEAN and alternative imaging algorithms;
      b) Image defects;
      c) Self-calibration;
   6) Digital Beamforming:
      a) 3D path difference;
      b) Array element signal;
      c) Array factor;
      d) Beam steering

Chapter 3 - Special Applications and Challenges:

   1) Surveys and Wide-Field Imaging;
   2) Low-frequency Challenges in Interferometry;
   3) Very Long Baseline Interferometry:
      a) Differences between VLBI and convertional interferometry;
      b) VLBI-systems;
      c) The VLBI processor;
      d) Retarded baselines;
      e) Closure relations;
      f) Image reconstruction;
   4) Spectroscopy in Radio Interferometry:
      a) Cross-correlation and correlators;
      b) Analysis of spectral lines;
   5) Polarization in Radio Interferometry:
      a) Stokes visibilities;
      b) Linear polarization;
      c) Faraday rotation;
      d) Circular polarization;
   6) Time-Domain Science in Radio Interferometry;
   7) Big Data in Radio Interferometry;
   8) Interferometry and Geodesy

Chapter 4 - Technical Realization: Current and Upcoming Radio Interferometers

   1) Low-frequency arrays;
   2) Centimeter-band arrays;
   3) (Sub-) Millimeter arrays;
   4) Upcoming arrays

Detaillierter Inhalt:

This course is divided into four chapters: Motivation and background, fundamental concepts, special applications and challenges and technical realization: current and upcoming radio interferometers. In the first chapter, a historical overview of the development of radio interferometry as well as an overview of the main scientific applications of radio interferometry is given. In the second chapter, the mathematical basics and physical concepts of radio interferometry are introduced that are necessary for the understanding of the later sections. The focus of this chapter is on the aperture synthesis in radio-interferometric arrays, receiver systems and image reconstruction. In chapter 3 special applications in radio interferometry are discussed in more detail. Here, the technique of Very Long Baseline Interferometry is discussed in detail. In addition, applications on polarimetry, spectroscopy, surveys, low-frequency and time-resolved measurements, big data aspects and geodesy are also discussed. In chapter 4, links to important radio interferometers in current research are given. Students learn to be able to independently assess which instruments are suitable for given scientific questions.

Lern-/Qualifikationsziele:

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Lehrveranstaltungstyp:

Kurs

Interaktionsformen mit Betreuer/in:

E-Mail, Übungsaufgaben

Interaktionsformen mit Mitlernenden:

Chat, Forum

Kursdemo:

zur Kursdemo

Nutzung

Kurs ist konzipiert für:

Uni Würzburg:

• Physik (Master)
• Physics international (Master)

FAU Erlangen-Nürnberg:

• Physik (Master)
• Elitestudiengang Physik mit integrierten Doktorandenkolleg (Master)
• Lehramt Physik
• Ingenieurwiss. Studiengänge (insbes. Informatik) (Master)

TU München:

• Geodäsie und Geoinformatik (Master)
• Earth Oriented Space Science and Technology (ESPACE) (Master)

LMU München:

• Physik (Master)
• Astrophysik (Master)

Formale Voraussetzungen:

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Erforderliche Vorkenntnisse:

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Hinweise zur Nutzung:

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Kursumsetzung (verwendete Medien):

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Erforderliche Technik:

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Nutzungsentgelte:

für andere Personen als (reguläre) Studenten der vhb Trägerhochschulen nach Maßgabe der Benutzungs- und Entgeltordnung der vhb

Rechte hinsichtlich des Kursmaterials:

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Verantwortlich

Anbieterhochschule:

Uni Würzburg

Anbieter:

Prof. Dr. Matthias Kadler

Prof. Dr. Jörn Wilms

Prof. Dr. Urs Hugentobler

Prof. Dr. Joseph Mohr

Autoren:

Florian Rösch

Alexander Kappes

Matthias Kadler

Jörn Wilms

Betreuer:

Prof. Dr. Matthias Kadler

Prüfung

Project Report for "Radio-Astronomical Interferometry"

Art der Prüfung:

Projektarbeit

Bemerkung:

Project Report for "Radio-Astronomical Interferometry"

Prüfer:

Prof. Dr. Matthias Kadler

Prüfungsanmeldung erforderlich:

ja

Anmeldeverfahren:

Anmeldung per E-Mail

Prüfungsanmeldefrist:

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Prüfungsabmeldefrist:

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Kapazität:

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Prüfungsdatum:

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Prüfungszeitraum:

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Prüfungsdauer:

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Prüfungsort:

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Zuständiges Prüfungsamt:

Anerkennung: Heimathochschule

Zugelassene Hilfsmittel:

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Formale Voraussetzungen für die Prüfungsteilnahme:

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Inhaltliche Voraussetzungen für die Prüfungsteilnahme:

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Zertifikat:

Ja (Benoteter Schein)

Anerkennung:

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