Asian Radio Astronomy Winter School 2007
VLBI Data Reduction Course

Written by Seiji Kameno (Kagoshima University, Japan)
Translated and edited by Tomoharu Kurayama
(VERA, National Astronomical Observatory of Japan, Japan)
Japanese version

We are going to analyze the data observing a simple-structure radio source DA193. The observation frequency is 15 GHz. The VLBA stations are used, and the observation time is only about 20 minutes. Although this is very short observation, the map dynamic range exceeds 1000. At first, let’s see the results.


(u, v) plot


Final image

Observation parameters

Observation date2001 August 17
VLBI arrayVLBA (10 stations)
Observed sourcesDA193 (Note: Originally the target source of this observation is NGC1052. DA193 is observed for calibration.)
Observation frequency15.4 GHz
Bandwidth16 MHz × 2 IF, 64 frequency channels/IF
Data size97.3 MB

Procedure of analysis

We are going to analyze the data with AIPS and difmap. We carry out the data calibration mainly with AIPS, and imaging and self-calibration with difmap.

  1. Processing by AIPS
    Lesson 1.
    Loading data into AIPS
    Lesson 2.
    Confirming the data
    Lesson 3.
    Calibrating amplitudes of visibilities
    Lesson 4.
    Fringe fitting (calibration of delay)
    Lesson 5.
    Bandpass calibration (calibration of frequency characteristics)
    Lesson 6.
    Reducing data size by frequency integration
    Lesson 7.
    Creating FITS file in order to image with difmap
  2. Processing by difmap
    Lesson 8.
    Loading data into difmap
    Lesson 9.
    Displaying visibilities and time integration
    Lesson 10.
    Fragging bad data (avoiding bad data from analysis)
    Lesson 11.
    Creating a dirty map
    Lesson 12.
    Lesson 13.
    Self-calibration of phase
    Lesson 14.
    Self-calibration of amplitude
    Lesson 15.
    Creating a final image