This utility is still under construction. Users may experience delays in retrieval, outright failures, and errant data points. The phrase 'caveat emptor' certainly applies.
2) Select the desired wavelength. This will automatically invoke the plot. The wavelength bands correspond to the following frequencies: 90cm (P) = 0.302 -> 0.35 GHz; 20cm (L) = 1.36 -> 1.54 GHz; 6cm (C) = 4.81 -> 4.91 GHz; 3.6cm (X) = 8.41 -> 8.51 GHz; 2cm (U) = 14.89 -> 14.99 GHz; 1cm (K) = 22.41 -> 22.51 GHz; 0.7cm (Q) = 43.29 -> 43.39 GHz
The default mode of operation is to plot data from the last 60 days. The number of points plotted is described at the bottom of the plot. The Start and Stop times for the plot will be shown in the boxes marked. These fields can be editted to change the time range that the user would like to search. Use the windowing features described below to zoom the plot.
Flux densities are plotted for the AC and BD IF pairs as available. Most VLA observations record simultaneously at two independently tunable frequencies.
Accuracy of the measurements at X and C bands is better than 10%. At U and L bands it is generally within 10% although spurious measurements are more common. At P band measurements have much larger errors due to the higher system temperatures and more narrow bandwidths employed. RFI may also be problematic at P and L bands. At K and Q bands the atmosphere and antenna gain as a function of elevation introduce considerable scatter into the measurements. To reduce this scatter somewhat, only observations taken between 30 and 80 degrees are entered into the database. The accuracy here is still probably not much better than 50% but could be improved. Pointing errors at high frequencies may also introduce some poor measurements into the database.
No uv-restrictions are currently employed in the ANTSOL solutions so resolution effects _will_ be present. These effects and the effects of confusion will become more significant as we move into the smaller configurations.
Plots can be "zoomed" to reveal a time/flux range of interest.
Above 10 GHz observations below 30 degrees and above 80 degrees in elevation are discarded.
A table of raw measurements, frow which each plot is derived, can be examined in the Java console. And since the data is contained in an AIPS++ table, various other applications can be fairly readily built as the need arises.
Comments? Send them to firstname.lastname@example.org
Last Modified on 2006 Apr. 13
Return to the VLA Calibrator page , or to the Calibrator Flux History Database