Fringe Finder Survey

VLBA Test Memo #60

VLBA Fringe-Finder Survey

A. G. Markowitz and J. D. Wurnig

Advisor: J. Wrobel

• Observed under project code TF015--all 10 VLBA antennas, no VLA or other stations.
• For each source, we observed two scans of 5.5 minutes = 11 minutes total dwell time each for all wavelengths except 7mm/43GHz (four scans of 5.5 minutes each = 22 minutes total dwell time). Optimum UV coverage is advertised.
• RR selected in DIFMAP
• Tony Beasley's VLBA Calibrator Survey is a search engine for hundreds of sources, not just the biggest & brightest. S-band (13cm) & X-band (4cm) UV plots & contour images, as well as position information, are provided.
• Be sure to read 'Notes' column for each source for important additional information

Notes:

1. Observed under project code TF015A, 24-25 Nov. 1997. For this epoch, HN had high Tsys values throughout the project due to snow and ice in the dish, leading to amplitude errors during calibration. In order to recover HN, we found it necessary for us to use DIFMAP to construct a model without HN, then use that model to calibrate the full data set.  The noise factor associated with HN is therefore somewhat amplified. In the visibility plots, all baselines to HN have correct amplitude, but a larger than normal scatter due to the noise.
2. No FRING solutions were found for HN at Q-band (7mm) for any of the seven sources observed during the TF015A.971124 epoch; HN is therefore omitted from final Q-band UVPLT & contour plots for these sources.
3. Very poor FRING solutions were found for HN at U-band (2cm) for 0234+285, 2007+777 & 3C345. (TF015A.971124)
4. No FRING solutions found for HN at K-band (1cm) for 0234+285, 3C84, 3C345, 2007+777 & 3C454.3; HN is omitted from final K-band UVPLT & contour plots for these sources. (TF015A.971124)
5. For the TF015A.971124 epoch, MK's L-band compressor was experiencing some difficulties, and MK had high noise. Most of this was corrected with DIFMAP, but MK is still a bit noisy for 0234+285 & 2007+777.
6. For 2007+777 (obs. TF015A.971124) at Q-band (7mm), SC had missing or poor solutions for most time spent on this source; what little SC when on 2007+777 exists is noisy (in addition to no HN solutions found).
7. For 3C345 & 0234+285 (obs. TF015A.971124) at Q-band (7mm), we used DIFMAP to correct for abnormal amplitudes at SC.
8. For the TF015B.980426 epoch, LA had rain (and high Tsys) for the first several hours; PT had rain & fog (and high Tsys) for the last hour of the project. The resultant low amplitudes for PT & LA were corrected with DIFMAP, but both stations are still a bit noisy. LA had no 7mm data due to a receiver problem.
9. For 0528+134 L-band, MK is absent from the first 5.5 minute scan.
10. Observed under project code TF015H on 2000Jul16.