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Correcting atmospheric path variations in millimeter wavelength very long baseline interferometry using a scanning water vapor spectrometer
Author(s) -
Tahmoush David A.,
Rogers Alan E. E.
Publication year - 2000
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/2000rs002334
Subject(s) - water vapor , millimeter , radiometer , optics , interferometry , very long baseline interferometry , wavelength , remote sensing , path length , troposphere , spectrometer , coherence (philosophical gambling strategy) , environmental science , extremely high frequency , physics , materials science , atmospheric sciences , astrophysics , meteorology , geology , quantum mechanics
The coherence of very long baseline interferometry (VLBI) at millimeter wavelengths can be improved through the use of a water vapor radiometer (WVR) to estimate the atmospheric path length variations along the line of sight to each antenna. Measurements of the water vapor emission spectrum using a simple scanning WVR have been used to correct the interferometer phases, thereby lowering the rms phase variation and increasing the coherence time. The average improvement in the coherent fringe amplitude of 400 s VLBI scans at 3 mm wavelength was 20% with a general trend of a greater improvement for the scans with larger phase variations. Sampling of the spectrum from 18 to 26 GHz allows separation of the water vapor emission from instrumental effects and from the emission of water droplets in clouds. The observed line profiles favor the Van Vleck‐Weisskopf line shape.