The purpose is to do a survey of calibrators listed in the VLA Calibrator Manual in the EOVSA frequency range (2.5-18 GHz) to determine their spectral shapes. The results are very useful to determine whether or not a phase calibrator in question is suitable for the entire EOVSA bandwidth or is only usable for a fraction of the bandwidth. It is also valuable to test the sensitivity limit of EOVSA's 27-m + 2-m baseline within a reasonable amount of integration time (10 minutes). The best calibrator sources are those 1) bright enough over the entire band (within ~10 min of integration), and 2) show a rather flat visibility vs. UV distance curve (point source).
Bin wrote a routine named "eovsa_src_visibility.py" on helios. Dale upgraded it with more user-friendly features named "dg_src_visibility.py". They display the visibility of all VLA calibrators by the 27-m antenna above a certain flux density threshold (defined by parameter "minflux") in C band for a given time and duration. An example of this plot is shown in Fig. 1: X-axis is time and Y-axis is the source altitude.