1. AIPS

2. WSRT & VLA Y-shape array A - 21 km B - 10 km C - 3.6 km D - 0.6 km
27 telescopes Ø25m
east - west array
~ 2.8 km
14 telescopes Ø25m

3. GMRT & MERLIN random centre & Y-shape array 30 km 30 telescopes Ø45m
Lovel Ø76m

4. VLBA &
EVN & VLBI
10 telescopes Ø25m

5. UV-coverage

6. dirty &
clean Image

7. UV coverage & Image
12 hours WSRT observations

8. Clean Image I

9. Clean Image II

10. Why Calibration and Editing?
Synthesis radio telescopes, though well-designed, are not perfect
(e.g., surface accuracy, receiver noise, polarization purity, stability, etc.)
Need to accommodate engineering
(e.g., frequency conversion, digital electronics, etc.)
Hardware or control software occasionally fails or behaves unpredictably
Scheduling/observation errors sometimes occur (e.g., wrong source positions)
Atmospheric conditions not ideal (not limited to “bad” weather)
RFI radio frequency interference

11. That's why!
BAD GOOD

12. visibilities = amplitude[t] * e(i[t])
VLA observations
amplitude versus time
good diagnostic for bad data
amplitude versus UV distance

13. www-astro.physics.ox.ac.uk/~hrk/AIPS_TUTORIAL/HRK_AIPS_1.html