|Date||Band||Project Code||Backend(s)||Types of Data|
|2003 October 19||400-450 MHz||TRFI450_OCT19||ACS(50MHz)||Az rotation|
Plot 15A shows the uncalibrated data for scan
15 averaged over all directions. Major RFI spikes are seen at
409.8, 422.8, and 432-434 MHz.
Plot 16A shows the uncalibrated data for scan 16 averaged over all directions.
Plot 18A shows the uncalibrated data for scan 18 averaged over all directions. Major RFI spikes are seen at 443-446 MHz, 409 MHz, and 432 MHz.
Doing median filter subtraction on all 599 integrations of 32786-channel spectra proved to be too time-consuming. The spectra were averaged to reduce the number of channels to 4096, increasing the channel spacing to 12.2 kHz. The data were calibrated and converted to units of Janskys (10**-26 Watts/sq.meter/Hz). A median-filtered baseline was subtracted to flatten the bandpass. A 7-point median filter was used on scans 15 and 16, 5-point on 18.
Plot 18B shows the calibrated data for scan 18 and integration number 599 after baseline flattening.
RFI spikes were identified as any data point exceeding 3.0 times the rms in the baseline-flattened spectra.
Plot 18C shows the same data as in plot 18B, with the identified RFI spikes superimposed in green.
Plot 18D shows the typical run of rms with frequency, for integration number 184. The rms was calculated over a 21-channel (256 kHz) window centered on each point in the spectrum. Outliers above 2.6 times the rms were thrown out and the rms re-calculated, so that the rms was not contaminated by RFI spikes. This procedure was sometimes overwhelmed by very large and wide RFI signals. In these cases, the rfi was so large that it was identified anyway.
Note that the typical rms ranges from 0.2 to 0.6 Jy across the spectrum. This may be a combination of the noise predicted by the radiometer equation (0.12 Jy) and confusion (0.5 Jy). The drop in rms at the band edges is probably bogus. In fact, the change in rms across the band is probably bogus because we used a single value for Tcal and deltacal for the whole band.
Scan 15, 594 2-second integrations.
Sweep from 0 up to 360 azimuth. Taken Oct 19, 02:46-03:06 AM (EDT) (34 MB)
Scan 16, 594 2-second integrations. Sweep from 360 to 0 azimuth. Taken Oct 19, 03:07-03:27 AM (EDT) (34 MB)
Scan 18, 599 2-second integrations. Sweep from 360 to 0 azimuth. Taken Oct 19, 11:20-11:40 AM (EDT) (34 MB)