Astrophysics (Index)About

baseline

(distance between dishes of an interferometer)

The term baseline, in interferometry, such as in radio astronomy, is used for the line between two telescopes (e.g., dishes) that comprise part of interferometer. The term is also commonly used for the length of this line, i.e., the distance between the two. This distance contributes to the angular resolution that can be discerned, e.g., through aperture synthesis. For an array of multiple dishes, often a maximum baseline is cited, i.e., the distance between the furthest two dishes, and if they are movable, e.g., on tracks, the distance when they are moved as far as the tracks allow. The potential angular resolution is inversely proportional to the baseline length, but also depends upon the wavelength. This resolution is only for angles of the sky across the direction of the baseline, so multiple dishes with more than one baseline are used, as well as moving dishes around on tracks, and using the rotation of Earth to produce baselines over different directions in relation to the target object.


The term baseline is also used in astronomy in a more general sense, as a reference level of some measurement, signal or statistic, usually a selected typical level. The term is also used, analogously to the interferometry meaning, for other cases where some distance or measure is of interest, e.g., the distance between two observations in parallax determination, or the time interval between two observations aimed at determining proper motion.


(interferometry,measure)
Further reading:
https://en.wikipedia.org/wiki/Aperture_synthesis
http://astronomy.swin.edu.au/cosmos/B/Baseline
http://planetfacts.org/baseline/
https://en.wiktionary.org/wiki/baseline

Referenced by pages:
angular resolution
aperture
aperture masking interferometry (AMI)
aperture synthesis
Australia Telescope Compact Array (ATCA)
CHARA
CLEAN
COAST
Combined Array for Research in Millimeter-wave Astronomy (CARMA)
Cosmic Anisotropy Telescope (CAT)
dirty image
Earth rotation synthesis
Earth-sized VLBI
electronic very-long-baseline interferometry (e-VLBI)
European Southern Observatory Very Large Telescope (ESO VLT)
Event Horizon Telescope (EHT)
GI2T
Giant Metrewave Radio Telescope (GMRT)
Greenland Telescope (GLT)
HERA
high-resolution imaging
IOTA
Keck Observatory
Long Baseline Array (LBA)
Low-frequency Array (LOFAR)
MeerKAT
MRO Interferometer (MROI)
Murchison Widefield Array (MWA)
Next Generation Very Large Array (ngVLA)
Northern Extended Millimeter Array (NOEMA)
Palomar Testbed Interferometer (PTI)
parallax
Plateau de Bure Interferometer (PdBI)
pulsar timing array (PTA)
Radio Camera Initiative (RCI)
Submillimeter Array (SMA)
SUSI
VERA
Very Large Array (VLA)
Very Long Baseline Array (VLBA)
very-long-baseline interferometry (VLBI)
visibility

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