Lecture

Radio Telescope Calibration

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Description

This lecture covers the calibration process for radio telescopes, focusing on cross-calibration and bandpass calibration. It explains the use of Jones matrices and the Radio Interferometry Measurement Equation (RIME) to correct for atmospheric effects, antenna beam patterns, and receiver gains. The importance of calibrator sources with known properties is highlighted, along with the calibration of absolute flux scale and complex gain variations. The instructor demonstrates the use of CASA software tools for calibration, including setjy for filling model columns, gaincal for temporal gains determination, and plotcal for visualizing calibration results.

In MOOC

The Radio Sky II: Observational Radio Astronomy

The first part of the course introduces the different types of telescope technologies available to astronomers, with a particular focus on single-dish radio telescopes and radio interferometers. Optical, UV, X-ray, Gamma, neutrino, and gravitational wave telescopes will also be briefly covered, as well as a foray into Search for Extraterrestrial Intelligence. We, then, dive deep into the principles of observational radio astronomy, covering the observables (flux, luminosity, brightness temperature), and th

Official source

Related concepts (32)

Absolute magnitude

Absolute magnitude (M) is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it were viewed from a distance of exactly , without extinction (or dimming) of its light due to absorption by interstellar matter and cosmic dust. By hypothetically placing all objects at a standard reference distance from the observer, their luminosities can be directly compared among each other on a magnitude scale.

Magnitude (astronomy)

In astronomy, magnitude is measure of the brightness of an object, usually in a defined passband. An imprecise but systematic determination of the magnitude of objects was introduced in ancient times by Hipparchus. Magnitude values do not have a unit. The scale is logarithmic and defined such that a magnitude 1 star is exactly 100 times brighter than a magnitude 6 star. Thus each step of one magnitude is times brighter than the magnitude 1 higher.

Direct-conversion receiver

A direct-conversion receiver (DCR), also known as homodyne, synchrodyne, or zero-IF receiver, is a radio receiver design that demodulates the incoming radio signal using synchronous detection driven by a local oscillator whose frequency is identical to, or very close to the carrier frequency of the intended signal. This is in contrast to the standard superheterodyne receiver where this is accomplished only after an initial conversion to an intermediate frequency.

Luminosity

Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a star, galaxy, or other astronomical objects. In SI units, luminosity is measured in joules per second, or watts. In astronomy, values for luminosity are often given in the terms of the luminosity of the Sun, L⊙.

Superheterodyne receiver

A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency. It was long believed to have been invented by US engineer Edwin Armstrong, but after some controversy the earliest patent for the invention is now credited to French radio engineer and radio manufacturer Lucien Lévy. Virtually all modern radio receivers use the superheterodyne principle.

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