Mediaspace scheduled maintenance: Aug 25, 2026 07:00 - 12:00 AM. During this time, videos will be temporarily unavailable. Check status updates.

Lecture

Radio Telescope Calibration

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

Official source

Related concepts (32)

Radio telescope

A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects, just as optical telescopes are the main observing instrument used in traditional optical astronomy which studies the light wave portion of the spectrum coming from astronomical objects.

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.

Antenna array

An antenna array (or array antenna) is a set of multiple connected antennas which work together as a single antenna, to transmit or receive radio waves. The individual antennas (called elements) are usually connected to a single receiver or transmitter by feedlines that feed the power to the elements in a specific phase relationship. The radio waves radiated by each individual antenna combine and superpose, adding together (interfering constructively) to enhance the power radiated in desired directions, and cancelling (interfering destructively) to reduce the power radiated in other directions.

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.

Related lectures (46)

Radio Interferometry: The Universe At Radio Wavelengths MOOC: The Radio Sky II: Observational Radio Astronomy

Explores radio interferometry, MeerKAT telescope, imaging vs. single measurement, and Fourier transform in radio astronomy.

The Incredible Diversity of Radio Telescopes MOOC: The Radio Sky II: Observational Radio Astronomy

Explores the incredible diversity of radio telescopes and covers primary beam patterns, sensitivity calculations, and historical significance.