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Surveys are essential for marking property boundaries near water bodies. Different types of surveys are defined, each with its own function. Land surveys mark the property boundaries, while route surveys determine the position of properties on nearby highways. Topographic surveys create maps by capturing the three-dimensional features of the land. Hydrographic surveys focus on the shapes of underwater areas and the movement of streams through the properties. Mine surveys determine the relative...
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Related Experiment Video

Updated: Feb 8, 2026

Methods for Image-based Surveys of Benthic Macroinvertebrates and Their Habitat Exemplified by the Drop Camera Survey for the Atlantic Sea Scallop
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Second Epoch VLBA Calibrator Survey Observations - VCS-II.

David Gordon1, Christopher Jacobs2, Anthony Beasley3

  • 1NVI Inc @ NASA Goddard Space Flight Center, Code 698.2, Greenbelt, MD 20771, David.Gordon-1@nasa.gov.

The Astronomical Journal
|June 26, 2018
PubMed
Summary
This summary is machine-generated.

The VLBA Calibrator Survey (VCS-II) re-observed 2400 radio sources, significantly improving their positional accuracy. This enhances the International Celestial Reference Frame (ICRF3) and aids Very Long Baseline Interferometry (VLBI) calibrators.

Keywords:
astrometryquasars: generalradio continuum: galaxiesreference systemssurveystechniques: interferometric

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Area of Science:

  • Astronomy and Astrophysics
  • Geodesy
  • Radio Astronomy

Background:

  • The VLBA Calibrator Survey (VCS) has conducted six campaigns since 1994 to identify compact radio sources for VLBI phase reference calibration.
  • Accurate source positions are crucial for precise astrometry and the construction of celestial reference frames.

Purpose of the Study:

  • To report on the second epoch VLBA Calibrator Survey (VCS-II) observations.
  • To improve the International Celestial Reference Frame (ICRF3) through re-observation of VCS sources.
  • To enhance the utility of these sources as VLBI phase reference calibrators.

Main Methods:

  • Re-observation of 2400 previously cataloged VCS sources using the Very Long Baseline Array (VLBA) at X and S bands.
  • Detection of previously uncataloged sources.
  • Analysis of positional uncertainties and flux densities.

Main Results:

  • Revised positions for 2062 previously detected and 324 newly detected sources.
  • Reduction in average position uncertainties by a factor of approximately 5 (from ~1.14/1.98 mas to ~0.24/0.41 mas in RA/Dec).
  • Detection of sources with minimum flux values of ~15 mJy (X-band) and ~28 mJy (S-band), with median total fluxes of ~230/280 mJy.

Conclusions:

  • VCS-II significantly improved the positional accuracy of radio sources essential for ICRF3 and VLBI.
  • The survey identified a substantial number of new sources and refined positions for existing ones.
  • The results confirm the suitability of these flat-spectrum sources for high-precision astrometric applications.