Radio astronomy involves the observation and analysis of radio waves emitted by celestial objects to gain insights into their properties and behavior.

Interferometry in radio astronomy involves combining signals from multiple radio telescopes to achieve higher resolution and sensitivity, allowing astronomers to study celestial objects in greater detail.

Radio waves have the ability to penetrate interstellar dust and gas, allowing astronomers to study regions that are obscured by visible light, such as the centers of galaxies and dense molecular clouds.

Arecibo Observatory, located in Puerto Rico, was a single-dish radio telescope with a 305-meter dish that made significant contributions to radio astronomy before its collapse in 2020.

The Very Large Array (VLA) is a radio interferometer located in New Mexico, USA, and is primarily used to study the structure and evolution of galaxies, as well as other astronomical phenomena.

The Atacama Large Millimeter Array (ALMA) is a radio interferometer located in Chile and is renowned for its ability to observe radio waves at millimeter wavelengths, allowing astronomers to study cold gas and dust in galaxies and star-forming regions.

The Square Kilometer Array (SKA) project aims to construct the world's largest radio telescope with the goal of exploring the early universe, the formation and evolution of galaxies, and other fundamental questions in cosmology.

In interferometry, the process of combining signals from multiple radio telescopes is known as correlation, which involves aligning and comparing the signals to enhance the sensitivity and resolution of the observations.

The baseline length in interferometry refers to the distance between the radio telescopes. A longer baseline length provides higher resolution, allowing astronomers to distinguish finer details in the observed astronomical objects.

Fringe spacing in interferometry is the distance between adjacent fringes in the interference pattern. It is inversely proportional to the baseline length, and a smaller fringe spacing corresponds to higher angular resolution, enabling astronomers to resolve finer details in the observed astronomical objects.

Closure phase in interferometry refers to the phase difference between three or more antennas in an interferometer array. It is used to calibrate the phase errors and uncertainties in the interferometer, ensuring accurate and reliable measurements.

Self-calibration techniques in radio interferometry are employed to correct for instrumental and atmospheric effects that can distort the observed data. These techniques utilize the redundancy in the interferometric measurements to estimate and remove these effects, resulting in improved data quality and accuracy.

Aperture synthesis in radio interferometry involves combining signals from multiple radio telescopes to effectively create a larger virtual telescope. This technique allows astronomers to achieve higher angular resolution and sensitivity, enabling them to study astronomical objects in greater detail.

uv-coverage in radio interferometry refers to the distribution of baseline vectors in the uv-plane. It is crucial for determining the angular resolution of the synthesized images. A well-sampled uv-coverage ensures that the synthesized images have high angular resolution and accurately represent the observed astronomical objects.